# CYSTS OF THE JAWS DR. MAY LAM ORAL AND MAXILLOFACIAL RADIOLOGIST SENIOR LECTURER BDSC (HONS) FRACDS (GDP) DCLINDENT (DMFR) MRACDS (DMFR) Dr. May Lam Oral and Maxillofacial Radiologist Senior Lecturer BDSc (Hons) FRACDS (GDP) DClinDent (DMFR) MRACDS (DMFR) <h2>WHAT IS A CYST?</h2> <ul> <li><b>Definition:</b> a pathologic cavity filled with fluid, lined by epithelium, and surrounded by a definite connective tissue wall.</li> <li>Cysts occur more often in the jaws than in any other bone because most cysts originate from the numerous rests of odontogenic epithelium that remain after tooth formation.</li> <li>The cystic fluid either is secreted by the cells lining the cavity or is derived from the surrounding tissue fluid.</li> <li><b>Clinical Features:</b> asymptomatic swelling (most common)</li> </ul> - **Definition:** a pathologic cavity filled with fluid, lined by epithelium, and surrounded by a definite connective tissue wall. - Cysts occur more often in the jaws than in any other bone because most cysts originate from the numerous rests of odontogenic epithelium that remain after tooth formation. - The cystic fluid either is secreted by the cells lining the cavity or is derived from the surrounding tissue fluid. - **Clinical Features:** asymptomatic swelling (most common) - ==Some cysts produce a hard swelling==. **GENERAL IMAGING FEATURES** • **Location:** – Within bone anywhere in the maxilla or mandible (rare in condyle and coronoid process) – Odontogenic cysts occur in tooth-bearing regions of the jaws (above IAC) • **Periphery/Shape:** – Usually spherical/round, but its shape is influenced by adjacent structures – Well-defined, corticated • If secondarily infected, this may change to a thicker, sclerotic border or make the cortex less apparent   #### Location - Within bone anywhere in the maxilla or mandible (rare in condyle and coronoid process) - Odontogenic cysts occur in tooth-bearing regions of the jaws (above IAC) #### Periphery/Shape - Usually spherical/round, but its shape is influenced by adjacent structures - Well-defined, corticated - If secondarily infected, this may change to a thicker, sclerotic border or make the cortex less apparent - ==In the maxilla, odontogenic cysts are generally below the floor of the maxillary antrum==. - ==A cyst suspended in the maxillary sinus may grow concentrically and remain spherical==. - ==A cyst contacting thick cortical bone may develop a flattened edge==. - ==The well-defined, corticated border is usually thin and uniform==. Two periapical radiographs of the posterior mandible displaying well-defined, corticated radiolucencies located in tooth-bearing regions. Arrows on the upper image highlight the sclerotic border of a lesion associated with an impacted third molar, while the lower image shows a similar cystic lesion situated between the roots of adjacent teeth. Radiograph: A dental X-ray of the mandible showing a well-defined, corticated radiolucent lesion located below the roots of the teeth. Three black arrows point to the distinct borders of this spherical lesion, illustrating the general imaging features described. # GENERAL IMAGING FEATURES * **Internal Structure:** * Mostly radiolucent * Long standing cysts may have dystrophic calcification (gives a sparse particulate appearance) * Some cysts have septa * **Effects on Surrounding Structures:** * Displacement and resorption of teeth * Expansion and thinning of the jaw cortices * Displacement of the inferior alveolar canal (IAC) * Elevation of the antral +/- nasal cortical floors White and Pharoah, 2014   #### Internal Structure - Mostly radiolucent - Long standing cysts may have dystrophic calcification (gives a sparse particulate appearance) - Some cysts have septa #### Effects on Surrounding Structures - Displacement and resorption of teeth - Expansion and thinning of the jaw cortices - Displacement of the inferior alveolar canal (IAC) - Elevation of the antral +/- nasal cortical floors *White and Pharoah, 2014* - ==Cysts are usually radiolucent because fluid is lucent on X-rays==. - ==Dystrophic calcifications in long-standing cysts appear as sparse, small radiopaque dots==. - ==Septa are seen as thin radiopaque lines==. - ==Expansion and thinning of the jaw cortices may be difficult to appreciate on periapical, bitewing, and panoramic radiographs==. - ==These cortical changes are more clearly demonstrated on CBCT and multislice CT==. - ==The inferior alveolar canal is commonly displaced in an inferior direction==. Radiograph: A dental X-ray showing the lower jaw with teeth, highlighting a large radiolucent area (cyst) indicated by black arrows. The image illustrates the displacement of tooth roots and the inferior alveolar canal caused by the lesion. A panoramic dental radiograph showing the full dentition and jaws. White arrows point to a large, well-defined radiolucent area in the left posterior mandible (patient's left) that has caused expansion and thinning of the inferior cortical border. **CYSTS OF THE JAWS** 1. Radicular cyst a. Residual radicular cyst 2. Dentigerous cyst 3. Odontogenic keratocyst 4. Inflammatory collateral cysts a. Mandibular buccal bifurcation cyst b. Paradental cyst 5. Lateral periodontal cyst and botryoid odontogenic cyst 6. Nasopalatine duct cyst 7. Surgical ciliated cyst 8. Orthokeratinised odontogenic cyst 9. Calcifying odontogenic cyst 10. Glandular odontogenic cyst 1. Radicular cyst 1. Residual radicular cyst 2. Dentigerous cyst 3. Odontogenic keratocyst 4. Inflammatory collateral cysts 1. Mandibular buccal bifurcation cyst 2. Paradental cyst 5. Lateral periodontal cyst and botryoid odontogenic cyst 6. Nasopalatine duct cyst 7. Surgical ciliated cyst 8. Orthokeratinised odontogenic cyst 9. Calcifying odontogenic cyst 10. Glandular odontogenic cyst **1. RADICULAR CYST** * **Definition:** An inflammatory odontogenic cyst associated with the root of a non-vital tooth * **Related terminology:** – Acceptable: periapical cyst, apical cyst – Not recommended: (Apical) periodontal cyst, inflammatory dental cyst, dental cyst * **Subtype:** Residual radicular cyst * **Epidemiology:** most common cyst in the jaw (60% of all odontogenic cysts) * **Age:** wide range, peak incidence in 4th – 5th decades of life * **Gender:** slight male predilection WHO, 2022   - **Definition:** An inflammatory odontogenic cyst associated with the root of a non-vital tooth - **Related terminology:** - Acceptable: periapical cyst, apical cyst - Not recommended: (Apical) periodontal cyst, inflammatory dental cyst, dental cyst - **Subtype:** Residual radicular cyst - **Epidemiology:** Most common cyst in the jaw (60% of all odontogenic cysts) - **Age:** Wide range, peak incidence in 4th–5th decades of life - **Gender:** Slight male predilection *WHO, 2022* - ==A residual radicular cyst remains after extraction when the cystic epithelium is left behind and continues to grow.== A dental radiograph showing the maxillary anterior region with a distinct, well-defined radiolucent area located at the root apices of two central incisors. This periapical lesion appears as a dark shadow surrounding the tips of the tooth roots. A dental radiograph (X-ray) showing a cross-section of the jawbone with teeth visible at the top. A distinct, circular radiolucent area (dark spot) is present in the lower right region, illustrating the appearance of a cyst. # 1. RADICULAR CYST * **Aetiology:** – Chronic inflammation at the apex of a non-vital tooth causes proliferation of the epithelial cell rests of Malassez (remnants of Hertwig’s epithelial root sheath) in the PDL * This forms the epithelial lining of the radicular cyst – A cyst cavity is formed and enlarges as a result of osmotic pressure and peripheral bone resorption * **Clinical Features:** – Always associated with a non-vital tooth – Asymptomatic, unless secondarily infected * There may be a history of dental pain or abscess – May cause bluish swelling * May feel bony and hard (cortex intact), crepitant (bone thinning), rubbery and fluctuant (cortex perforated) Dentine Reduced Dental Epithelium Predentine Pulp Enamel Cementum Precementum Cementoblast Epithelial Rest Cells of Malassez Hertwig's Root Epithelium Dentine Predentine Figure courtesy of Dr T Matias RACDS Oral Histology Orientation Course Booklet Cawson’s Essentials of Oral Pathology and Oral Medicine, 2008   #### Aetiology - Chronic inflammation at the apex of a non-vital tooth causes proliferation of the epithelial cell rests of Malassez (remnants of Hertwig's epithelial root sheath) in the PDL - This forms the epithelial lining of the radicular cyst - A cyst cavity is formed and enlarges as a result of osmotic pressure and peripheral bone resorption #### Clinical Features - Always associated with a non-vital tooth - Asymptomatic, unless secondarily infected - There may be a history of dental pain or abscess - May cause bluish swelling - May feel bony and hard (cortex intact), crepitant (bone thinning), rubbery and fluctuant (cortex perforated) #### Tooth Anatomy (Figure Labels) Dentine; Reduced Dental Epithelium; Predentine; Pulp; Enamel; Cementum; Precementum; Cementoblast; Epithelial Rest Cells of Malassez; Hertwig's Root Epithelium; Dentine; Predentine *Figure courtesy of Dr T Matias — RACDS Oral Histology Orientation Course Booklet* *Cawson's Essentials of Oral Pathology and Oral Medicine, 2008.* Labelled diagram showing the histological structure of a tooth root and its surrounding tissues, specifically highlighting the components involved in radicular cyst formation. The illustration identifies key anatomical layers including Enamel, Dentine, Predentine, Pulp, Cementum, Precementum, Cementoblast, Reduced Dental Epithelium, Hertwig's Root Epithelium, and the Epithelial Rest Cells of Malassez. Clinical photo: An intraoral photograph showing the floor of the mouth and the ventral surface of the tongue. A distinct, bluish-purple swelling is visible on the lateral aspect of the tongue/floor of mouth area, adjacent to the lower teeth. **1. RADICULAR CYST – IMAGING FEATURES** * **Location:** * Maxilla > Mandible * 40-50% arise in the anterior maxilla, followed by the posterior mandibular region * Epicentre at tooth apex * Unless associated with a lateral root canal (*Lateral radicular cyst*) * **Periphery/Shape:** * Well-defined, cortical border * Cortex may be sclerotic or lost if cyst is secondarily infected * Curved or circular * Unless influenced by surrounding structures * >10mm White and Pharoah, 2014   #### Location - Maxilla > Mandible - 40–50% arise in the anterior maxilla, followed by the posterior mandibular region - Epicentre at tooth apex - Unless associated with a lateral root canal (*Lateral radicular cyst*) #### Periphery/Shape - Well-defined, cortical border - Cortex may be sclerotic or lost if cyst is secondarily infected - Curved or circular - Unless influenced by surrounding structures - >10 mm *White and Pharoah, 2014.* - ==A periapical radiolucency smaller than 10 mm is considered apical periodontitis.== - ==The border may become thicker and sclerotic with inflammatory change, but less distinct with secondary infection.== - ==A periapical radiolucency smaller than 10 mm is considered apical periodontitis.== A radiograph of the anterior maxilla showing a well-defined, unilocular radiolucency associated with the apex of an incisor tooth. Two black arrows point to the superior border of the lesion, indicating its cortical periphery. A periapical radiograph of the anterior maxilla showing teeth with roots. An orange arrow points to a well-defined, circular radiolucency (dark area) at the apex of a tooth root, illustrating the typical location and shape of a radicular cyst. **1. RADICULAR CYST** **– IMAGING FEATURES** • **Internal Structure:** – Radiolucent – Dystrophic calcifications may develop in long-standing cysts • Sparsely distributed, small particulate radiopacities • **Surrounding Structures:** – Displacement and resorption of roots of adjacent teeth • Resorption pattern has curved outline • Can resorb the root(s) of the involved non-vital tooth (rare) – May extend into the maxillary sinus (sinus floor remains intact but is elevated) – Outer cortical plates may expand in curved or circular shape – May displace the IAC in an inferior direction White and Pharoah, 2014   #### Internal Structure - Radiolucent - Dystrophic calcifications may develop in long-standing cysts - Sparsely distributed, small particulate radiopacities #### Surrounding Structures - Displacement and resorption of roots of adjacent teeth - Resorption pattern has curved outline - Can resorb the root(s) of the involved non-vital tooth (rare) - May extend into the maxillary sinus (sinus floor remains intact but is elevated) - Outer cortical plates may expand in curved or circular shape - May displace the IAC in an inferior direction *White and Pharoah, 2014.* Radiograph: A periapical radiograph showing a large, well-defined radiolucent lesion (cyst) associated with the root of a tooth that has a dense radiopaque restoration. The image illustrates the displacement and resorption of adjacent tooth roots by the expanding cystic structure. Radiograph showing a periapical lesion associated with a tooth containing a radiopaque restoration. Two white arrows point to the distinct, curved corticated border of the radiolucent area, illustrating the expansion of the cyst. # 1. RADICULAR CYST * **Histopathology:** * **Epithelium:** non-keratinised stratified squamous epithelium that is proliferative with elongated rete pegs in a characteristic arcading pattern * +/- hyaline (Rushton) bodies, mucous (goblet) cells, or small areas of keratinisation * **Cyst wall:** inflamed fibrous tissue, often with foamy histiocytes * Deposits of cholesterol crystals (clefts) with foreign body giant cells are often seen and may form luminal nodules * Residual and long-standing cysts are less inflamed and have more regular thin epithelium Mixed inflammatory infiltrate Foamy histocytes Cawson’s Essentials of Oral Pathology and Oral Medicine, 2008      #### Histopathology - **Epithelium:** Non-keratinised stratified squamous epithelium that is proliferative with elongated rete pegs in a characteristic arcading pattern - +/- hyaline (Rushton) bodies, mucous (goblet) cells, or small areas of keratinisation - **Cyst wall:** Inflamed fibrous tissue, often with foamy histiocytes - Deposits of cholesterol crystals (clefts) with foreign body giant cells are often seen and may form luminal nodules - Residual and long-standing cysts are less inflamed and have more regular thin epithelium Figure labels: Mixed inflammatory infiltrate; Foamy histocytes *Cawson's Essentials of Oral Pathology and Oral Medicine, 2008.* Histological micrograph showing a cystic lesion with an epithelial lining arranged in a characteristic arcading pattern. Two yellow arrows point to the underlying fibrous connective tissue wall, which is heavily infiltrated by inflammatory cells. This is a photomicrograph of a histological section stained with H&E. It illustrates the characteristic arcading pattern of proliferating epithelium forming anastomosing strands, situated above a connective tissue wall heavily infiltrated by inflammatory cells. A histological micrograph showing several hyaline (Rushton) bodies within the connective tissue. These appear as curved, laminated structures with a characteristic pink-to-purple staining pattern, contrasting against the surrounding pale stroma. This is a histopathological micrograph showing a section of cyst lining epithelium. The image illustrates mucous metaplasia, characterized by numerous clear, vacuolated goblet cells interspersed within the dark-staining basal layer of the epithelium. Histopathology micrograph showing cholesterol clefts, which appear as empty needle-shaped spaces where crystals were dissolved during section preparation. Flattened multinucleate foreign body giant cells are visible lining the edges of several clefts within the inflamed fibrous tissue. 1. RADICULAR CYST • Treatment: – Extraction or root canal therapy of tooth and enucleation of cyst +/- apicoectomy – Healing: new bone grows into defect from periphery and may result in a radiating pattern resembling the spokes of a wheel • Recurrence: – rare, although may persist as residual cysts (may follow extraction or RCT alone) BOX_A: A 6 BOX_B: B BOX_C: Koong, 2017 Essential diagnostic criteria: 1. Non-vital tooth 2. Cyst lined by non-keratinising epithelium in characteristic arcading pattern    #### Treatment - Extraction or root canal therapy of tooth and enucleation of cyst +/- apicoectomy - Healing: new bone grows into defect from periphery and may result in a radiating pattern resembling the spokes of a wheel #### Recurrence - Rare, although may persist as residual cysts (may follow extraction or RCT alone) #### Essential Diagnostic Criteria 1. Non-vital tooth 2. Cyst lined by non-keratinising epithelium in characteristic arcading pattern *Koong, 2017.* - ==A central lucent area may persist because it contains fibrous scar tissue and is considered normal.== Axial CT scan of the midface showing a large radiolucent lesion in the left maxillary sinus that has expanded and thinned the surrounding bone, consistent with a radicular cyst. The right maxillary sinus appears clear for comparison. Coronal CT scan of the paranasal sinuses showing a large radiolucent lesion in the left maxillary sinus (indicated by white arrows) that displaces the medial wall and extends superiorly toward the orbit. A periapical radiograph showing the maxillary teeth with two white arrows pointing to a large, dark (radiolucent) area surrounding the root tips of the upper premolars/molars. This lesion represents the cystic defect described in the text as associated with non-vital teeth. **2. DENTIGEROUS CYST** * **Definition:** A developmental odontogenic cyst of the jaws surrounding the crown of an unerupted tooth, the lining attached to the cementoenamel junction (CEJ). * **Related terminology:** follicular cyst * **Subtype:** eruption cyst (a superficial dentigerous cyst over an erupting tooth in a child, usually a deciduous first molar) * **Epidemiology:** 2nd most common cyst in the jaws (~25% of all jaw cysts) * **Age:** wide range (5-83 years), peak incidence in 2nd – 3rd decades * **Gender:** 1.7 times more frequent in males Cawson’s Essentials of Oral Pathology and Oral Medicine, 2008  - **Definition:** A developmental odontogenic cyst of the jaws surrounding the crown of an unerupted tooth, the lining attached to the cementoenamel junction (CEJ). - **Related terminology:** follicular cyst - **Subtype:** eruption cyst (a superficial dentigerous cyst over an erupting tooth in a child, usually a deciduous first molar) - **Epidemiology:** 2nd most common cyst in the jaws (~25% of all jaw cysts) - **Age:** wide range (5–83 years), peak incidence in 2nd–3rd decades - **Gender:** 1.7 times more frequent in males *Cawson's Essentials of Oral Pathology and Oral Medicine, 2008.* - ==An eruption cyst is located entirely within soft tissue above an erupting tooth.== - ==In children, dentigerous cysts account for approximately 25% of jaw cysts.== Clinical photo: An intraoral view showing a bluish, fluid-filled swelling on the alveolar ridge over an erupting tooth. The dark blue-purple coloration visible in the cyst cavity indicates bleeding into the space as a result of trauma. # 2. DC * **Aetiology:** – Develops from accumulation of fluid between the reduced enamel epithelium and crown of the unerupted tooth * **Clinical Features:** – Asymptomatic and usually discovered on routine dental radiographs or when investigating the failure of a tooth to erupt – Larger cysts cause slow expansion of jaw (hard swelling) – Pain and swelling if infected (usually due to communication with oral cavity) Cawson’s Essentials of Oral Pathology and Oral Medicine, 2008  #### Aetiology - Develops from accumulation of fluid between the reduced enamel epithelium and crown of the unerupted tooth #### Clinical Features - Asymptomatic and usually discovered on routine dental radiographs or when investigating the failure of a tooth to erupt - Larger cysts cause slow expansion of jaw (hard swelling) - Pain and swelling if infected (usually due to communication with oral cavity) *Cawson's Essentials of Oral Pathology and Oral Medicine, 2008.* A gross pathology specimen showing a surgically removed dentigerous cyst attached to an extracted tooth. The cystic sac surrounds the crown of the tooth, with the roots protruding from the base of the lesion. **2. DC – IMAGING FEATURES** • **Location:** – ~75% associated with unerupted mandibular 3rd molar – Lower 8s > Upper 3s > Upper 8s > Lower 5s – ~5% around supernumerary teeth (esp. mesiodens in anterior maxilla) – Epicentre above crown – Cyst attaches at CEJ • **Periphery/Shape:** – Well-defined corticated (may be missing if secondarily infected) – Curved or circular outline – More likely cystic if follicular cortex is >5mm from crown surface White and Pharoah, 2014   #### Location - ~75% associated with unerupted mandibular 3rd molar - Frequency: lower 8s > upper 3s > upper 8s > lower 5s - ~5% around supernumerary teeth (esp. mesiodens in anterior maxilla) - Epicentre above crown - Cyst attaches at CEJ #### Periphery and Shape - Well-defined corticated (may be missing if secondarily infected) - Curved or circular outline - More likely cystic if follicular cortex is >5 mm from crown surface *White and Pharoah, 2014.* Radiograph: A dental panoramic X-ray showing the lower jaw with an impacted third molar (wisdom tooth) associated with a large, well-defined radiolucent cystic lesion surrounding its crown. Radiograph: A dental panoramic X-ray showing an impacted mandibular third molar (wisdom tooth) surrounded by a well-defined radiolucent area, characteristic of a dentigerous cyst. **2. DC – IMAGING FEATURES** • **Internal Structure:** – Radiolucent, except crown of tooth • **Surrounding Structures:** – Displacement and resorption of adjacent teeth – Displacement of involved tooth – Displacement of maxillary antrum/IAC – Expansion of outer cortex of involved jaw White and Pharoah, 2014     #### Internal Structure - Radiolucent, except crown of tooth #### Surrounding Structures - Displacement and resorption of adjacent teeth - Displacement of involved tooth - Displacement of maxillary antrum/IAC - Expansion of outer cortex of involved jaw *White and Pharoah, 2014.* > [!note] Lecturer — Imaging Displacement > The cyst may displace developing teeth, including mandibular second molars and premolars. > > - In the maxilla, it may elevate the maxillary antral floor. > - In the mandible, it may displace the inferior alveolar canal inferiorly. > - Expansion of the outer cortex may be difficult to appreciate on two-dimensional imaging. Radiograph: A dental X-ray showing a radiolucent lesion (indicated by the white arrow) adjacent to the root of a tooth, illustrating an internal structure feature. Radiograph: A dental X-ray showing a large, well-defined radiolucent lesion in the posterior mandible. The lesion surrounds the crown of an impacted tooth and has displaced adjacent teeth inferiorly. Radiograph: A dental X-ray showing a large, well-defined radiolucent area surrounding the crown of an impacted tooth (likely a third molar). The image illustrates the displacement of adjacent teeth and the expansion of the jaw cortex associated with the lesion. Radiograph: A cropped dental radiograph (likely a panoramic or periapical view) showing a large, well-defined radiolucent lesion in the jaw. The lesion surrounds the crown of an impacted tooth located in the upper right quadrant, consistent with the imaging features described for a dentigerous cyst. 2. DENTIGEROUS CYST • Histopathology: – Epithelium: thin, non-keratinized stratified squamous epithelial lining. • +/- cuboidal, columnar and ciliated cells • +/- mucous or sebaceous metaplasia • +/- Hyaline (Rushton) bodies and focal keratinisation – Cyst wall: loose, often myxoid, fibrous connective tissue and may contain occasional odontogenic epithelial rests A CEJ B C WHO classification of head and neck tumours, 2017    #### Histopathology - **Epithelium:** thin, non-keratinized stratified squamous epithelial lining - +/- cuboidal, columnar and ciliated cells - +/- mucous or sebaceous metaplasia - +/- hyaline (Rushton) bodies and focal keratinisation - **Cyst wall:** loose, often myxoid, fibrous connective tissue and may contain occasional odontogenic epithelial rests *Panels A, B, C; CEJ labelled on figure.* *WHO classification of head and neck tumours, 2017.* - ==Attachment of the cyst lining to the CEJ is the defining feature both radiographically and histopathologically.== A histopathology slide showing a cross-section of tissue with a thin, non-keratinized epithelial lining attached to the CEJ (cementoenamel junction). The cyst wall appears as loose connective tissue, and an arrow indicates a specific area of interest near the attachment site. This is a histopathology micrograph (labeled B) showing a cyst lining consisting of a thin, non-keratinized stratified squamous epithelium resting on a loose, often myxoid, fibrous connective tissue wall. A histopathology micrograph showing a cyst wall with a thin, non-keratinized stratified squamous epithelial lining overlying loose fibrous connective tissue. An orange arrow points to a clear vacuole within the basal layer of the epithelium, likely representing mucous or sebaceous metaplasia. **2. DENTIGEROUS CYST** * **Treatment:** – Surgical enucleation (may include removal of tooth) – Large cysts may require marsupialisation before removal – Marsupialisation of eruption cysts to allow affected tooth to erupt normally – Submit cyst lining for histology as benign/malignant tumours have been reported to arise (e.g. ameloblastomas, SCC, mucoepidermoid carcinoma) * **Recurrence:** – Do not recur **Essential diagnostic criteria:** 1. Well-defined radiolucency associated with the crown of an unerupted tooth 2. Epithelium and cyst wall attached to the CEJ of the unerupted tooth #### Treatment - Surgical enucleation (may include removal of tooth) - Large cysts may require marsupialisation before removal - Marsupialisation of eruption cysts to allow affected tooth to erupt normally - Submit cyst lining for histology as benign/malignant tumours have been reported to arise (e.g. ameloblastomas, SCC, mucoepidermoid carcinoma) #### Recurrence - Do not recur #### Essential Diagnostic Criteria 1. Well-defined radiolucency associated with the crown of an unerupted tooth 2. Epithelium and cyst wall attached to the CEJ of the unerupted tooth > [!note] Lecturer — Marsupialisation Purpose > Marsupialisation may be used to decompress a large cyst and reduce its size. > > - It may also stimulate peripheral bony healing. **3. ODONTOGENIC KERATOCYST** • **Definition:** a developmental odontogenic cyst that is characterized histologically by a thin parakeratinzed stratified squamous epithelial lining with palisaded and hyperchromatic basal cells and clinically by a tendency to recur after treatment. • **Related terminology:** keratocystic odontogenic tumour • **Epidemiology:** 3rd most common, ~10-20% of odontogenic cysts – 5% of all OKCs occur as part of naevoid basal cell carcinoma syndrome (NBCCS) (usually multiple and in younger patients) • **Age:** all ages, peak incidence 2nd – 3rd decade and smaller peak at 50-70 years • **Gender:** slight male predilection WHO, 2022  - **Definition:** a developmental odontogenic cyst that is characterized histologically by a thin parakeratinized stratified squamous epithelial lining with palisaded and hyperchromatic basal cells and clinically by a tendency to recur after treatment. - **Related terminology:** keratocystic odontogenic tumour - **Epidemiology:** 3rd most common, ~10–20% of odontogenic cysts - 5% of all OKCs occur as part of naevoid basal cell carcinoma syndrome (NBCCS) (usually multiple and in younger patients) - **Age:** all ages, peak incidence 2nd–3rd decade and smaller peak at 50–70 years - **Gender:** slight male predilection *WHO, 2022* - ==It is also known as Gorlin-Goltz syndrome when referring to the syndromic condition.== A cropped panoramic radiograph showing the posterior mandible and ramus. The image reveals a large, ill-defined radiolucent lesion extending from the molar region into the ascending ramus, causing displacement of tooth roots. **3. OKC** * **Aetiology:** – Arise from remnants of dental lamina – Mutations in the PTCH1 gene (tumour suppressor gene) * In syndromic cases and 80% of sporadic cases * **Clinical Features:** – Painless, unless secondarily infected – Lesions are often large at diagnosis due to insidious growth pattern (significant bone destruction, but minimal bone expansion) – Tooth displacement if lesion is large – Pathologic fracture risk – Aspiration reveals yellow, cheesy material (keratin) #### Aetiology - Arise from remnants of dental lamina - Mutations in the PTCH1 gene (tumour suppressor gene) - In syndromic cases and 80% of sporadic cases #### Clinical Features - Painless, unless secondarily infected - Lesions are often large at diagnosis due to insidious growth pattern (significant bone destruction, but minimal bone expansion) - Tooth displacement if lesion is large - Pathologic fracture risk - Aspiration reveals yellow, cheesy material (keratin) > [!note] Lecturer — PTCH1 Signalling > PTCH1 mutation or inactivation activates the SHH signalling pathway and produces abnormal epithelial proliferation. > [!note] Lecturer — Growth Pattern > The cyst tends to tunnel through bone between the cortices with minimal expansion. > > - A jaw fracture may occur because the bone has been hollowed out and replaced by fluid. # 3. OKC – IMAGING FEATURES • Location: – ~80% in mandible • Mostly posterior body and ramus • Epicentre superior to IAC – If found in posterior maxilla, often associated with NBCCS – Sometimes form around an unerupted tooth – Rarely extraosseous (in the gingiva) • Periphery/Shape: – Well-defined and corticated (unless secondarily infected) – Smooth, round/oval shape, or scalloped outline White and Pharoah, 2014   #### Location - ~80% in mandible - Mostly posterior body and ramus - Epicentre superior to IAC - If found in posterior maxilla, often associated with NBCCS - Sometimes form around an unerupted tooth - Rarely extraosseous (in the gingiva) #### Periphery and Shape - Well-defined and corticated (unless secondarily infected) - Smooth, round/oval shape, or scalloped outline *White and Pharoah, 2014* - ==Multislice CT is useful for assessing the lesion’s extent and any cortical perforation.== A dental radiograph (X-ray) showing the posterior mandible. It illustrates a large, well-defined radiolucent lesion with a corticated border that is associated with an impacted tooth. Radiograph: A panoramic dental X-ray of the posterior mandible showing a large, well-defined radiolucent lesion with a scalloped outline situated between and around the roots of the teeth. The lesion extends superiorly toward the alveolar crest and inferiorly toward the lower border of the mandible. **3. OKC –** **IMAGING FEATURES** • **Internal Structure:** – Radiolucent – Curved internal septa may be present = multilocular appearance • **Surrounding Structures:** – Minimal expansion for size • Except upper ramus and coronoid process – Cystic wall may contact soft tissue peripheral to outer cortex of mandible – Occasionally displace and resorb teeth – IAC displaced inferiorly – May invaginate and occupy the entire maxillary antrum White and Pharoah, 2014  #### Internal Structure - Radiolucent - Curved internal septa may be present = multilocular appearance #### Surrounding Structures - Minimal expansion for size - Except upper ramus and coronoid process - Cystic wall may contact soft tissue peripheral to outer cortex of mandible - Occasionally displace and resorb teeth - IAC displaced inferiorly - May invaginate and occupy the entire maxillary antrum *White and Pharoah, 2014* > [!note] Lecturer — Internal Septa > Large lesions may appear multilocular, but they are not considered true multilocular lesions with separate compartments. > > - The septa represent residual dense bone and are often incomplete rather than extending from cortex to cortex. > [!note] Lecturer — Ramus Expansion > In the ramus or coronoid process, the lesion may balloon out and cause marked thinning, expansion, or perforation. > [!note] Lecturer — Surgical Planning > Cortical perforation indicates contact with adjacent soft tissues and may affect surgical planning. Tooth displacement and resorption may occur but are less pronounced than with other cysts. The image displays three radiographic panels labeled A, B, and C. Panel A is a lateral jaw radiograph showing arrows pointing to specific anatomical features or lesions, while Panels B and C are axial CT scans of the mandible (lower jaw) at different levels. 3. OKC • Histopathology: – Epithelium: Thin, regular, folded parakeratinised epithelium 4-8 cell layers thick without rete ridges • + corrugated with parokeratin • +/- focal orthokeratosis • Characteristic palisading basal layer with hyperchromatic nuclei – Cyst wall: uninflamed fibrous wall – Satellite cysts are more common in NBCCS     #### Histopathology - **Epithelium:** thin, regular, folded parakeratinised epithelium 4–8 cell layers thick without rete ridges - Corrugated with parakeratin - +/- focal orthokeratosis - Characteristic palisading basal layer with hyperchromatic nuclei - **Cyst wall:** uninflamed fibrous wall - Satellite cysts are more common in NBCCS Histopathology: A photomicrograph of a cystic lesion showing a thin, regular, folded epithelial lining with a corrugated parakeratinized surface and a characteristic palisading basal layer of hyperchromatic nuclei. The underlying connective tissue wall appears uninflamed. A photomicrograph of an odontogenic keratocyst lining, showing a thin, regular epithelium with a palisaded basal layer. The dark nuclei of the basal cells are shifted away from the basement membrane towards the upper layers, illustrating the characteristic reversal of nuclear polarity. A histopathology micrograph showing a cystic epithelial lining with a basal layer exhibiting small, downward-projecting proliferations or 'buds' into the underlying connective tissue. The image illustrates the concept of basal cell budding, a feature associated with odontogenic keratocysts. A histological micrograph stained with hematoxylin and eosin showing a cyst wall composed of pink connective tissue. Within the fibrous stroma, there are multiple distinct islands and small cystic spaces lined by epithelium, illustrating the presence of satellite cysts. # 3. OKC * **Treatment:** – Need CT imaging to determine extent and location of any cortical perforations with soft tissue extension – Enucleation, marsupialisation or resection – Periodic post-tx clinical and radiographic examination – Submit for histopathology – odontogenic carcinoma arising from the epithelial lining of OKCs has been reported * **Recurrence:** – High recurrence rate with traditional enucleation (20-30%) * Even higher in NBCCS (50%) * Recurrence can be reduced by more aggressive or adjunctive treatment including curettage, resection, peripheral ostectomy, cryotherapy or chemical cautery of the cavity, with excision of overlying mucosa – Usually within first 5 years, but may occur as late as 10 years – Likely due to small satellite cysts or fragments of epithelium left behind after surgical removal **Essential diagnostic criteria:** 1. Located in jaws 2. Stratified squamous epithelial lining with surface parakeratin 3. Palisaded hyperchromatic basal cells #### Treatment - Need CT imaging to determine extent and location of any cortical perforations with soft tissue extension - Enucleation, marsupialisation or resection - Periodic post-treatment clinical and radiographic examination - Submit for histopathology — odontogenic carcinoma arising from the epithelial lining of OKCs has been reported #### Recurrence - High recurrence rate with traditional enucleation (20–30%) - Even higher in NBCCS (50%) - Recurrence can be reduced by more aggressive or adjunctive treatment including curettage, resection, peripheral ostectomy, cryotherapy or chemical cautery of the cavity, with excision of overlying mucosa - Usually within first 5 years, but may occur as late as 10 years - Likely due to small satellite cysts or fragments of epithelium left behind after surgical removal #### Essential Diagnostic Criteria 1. Located in jaws 2. Stratified squamous epithelial lining with surface parakeratin 3. Palisaded hyperchromatic basal cells - ==Marsupialisation may be used for decompression of larger lesions.== - ==More aggressive approaches may include ostectomy, cryotherapy or chemical cautery with Carnoy solution.== # 4. INFLAMMATORY COLLATERAL CYSTS * **Definition:** inflammatory cysts on the buccal or distobuccal aspect of the roots of partially or recently erupted teeth. * Two main types: – Paradental cysts (PC) (60%) – Mandibular buccal bifurcation cysts (MBBC) (40%) * **Epidemiology:** 5% of all odontogenic cysts * **Average age:** 30 years (PC); 9 years (1st molar MBBC); 17 years (2nd molar MBBC) * **Gender:** more common in males (70%)  - **Definition:** inflammatory cysts on the buccal or distobuccal aspect of the roots of partially or recently erupted teeth. - Two main types: - Paradental cysts (PC) (60%) - Mandibular buccal bifurcation cysts (MBBC) (40%) - **Epidemiology:** 5% of all odontogenic cysts - **Average age:** 30 years (PC); 9 years (1st molar MBBC); 17 years (2nd molar MBBC) - **Gender:** more common in males (70%) Radiograph: A panoramic dental X-ray (orthopantomogram) of a pediatric patient in the mixed dentition stage, showing developing permanent teeth and erupted primary molars. The image displays radiolucent areas associated with the roots of the lower first molars, consistent with the inflammatory collateral cysts discussed on the slide. # 4. ICC * **Aetiology:** – Inflammation and dilation of the pericoronal tissues and lined by sulcular/junctional epithelium (derived from reduced enamel epithelium) – Cyst formation may be exacerbated by food impaction or enamel cervical projections * **Clinical Features:** | Paradental Cysts | Mandibular Buccal Bifurcation Cysts | | :--- | :--- | | • History of longstanding pericoronitis, but often asymptomatic at presentation<br>• Pain, swelling, and trismus<br>• Tooth is vital | • May be infected with pain, tenderness, and suppuration<br>• Tooth is tilted buccally<br>• Deep periodontal pockets<br>• Delayed eruption of associated molar<br>• Tooth is vital |  #### Aetiology - Inflammation and dilation of the pericoronal tissues and lined by sulcular/junctional epithelium (derived from reduced enamel epithelium) - Cyst formation may be exacerbated by food impaction or enamel cervical projections #### Clinical Features | Paradental Cysts | Mandibular Buccal Bifurcation Cysts | | :--- | :--- | | • History of longstanding pericoronitis, but often asymptomatic at presentation<br>• Pain, swelling, and trismus<br>• Tooth is vital | • May be infected with pain, tenderness, and suppuration<br>• Tooth is tilted buccally<br>• Deep periodontal pockets<br>• Delayed eruption of associated molar<br>• Tooth is vital | - ==Enamel cervical projections may extend beyond the CEJ onto the root surface, particularly near the bifurcation==. A two-column comparison table contrasting the clinical features of Paradental Cysts and Mandibular Buccal Bifurcation Cysts. The left column lists symptoms such as history of pericoronitis, pain, swelling, trismus, and tooth vitality, while the right column details signs including infection, buccal tilting, deep periodontal pockets, delayed eruption, and tooth vitality. **4. ICC – IMAGING FEATURES** * **Location:** – PC: typically distobuccal aspect of mandibular 3rd molars (depending on angle of impaction) – MBBC: at the buccal aspect of mandibular 1st or 2nd molars and are often bilateral – Other sites: rare (4%) * **Periphery and Shape:** – May not be readily apparent with very subtle radiolucent region superimposed over the roots – Circular shape with well-defined cortical border – Can become quite large WHO, 2022  #### Location - PC: typically distobuccal aspect of mandibular 3rd molars (depending on angle of impaction) - MBBC: at the buccal aspect of mandibular 1st or 2nd molars and are often bilateral - Other sites: rare (4%) #### Periphery and Shape - May not be readily apparent with very subtle radiolucent region superimposed over the roots - Circular shape with well-defined cortical border - Can become quite large *WHO, 2022* Two dental radiographs (likely periapical views) showing impacted mandibular third molars. The images illustrate the characteristic pericoronal radiolucencies associated with odontogenic keratocysts, appearing as well-defined dark areas surrounding the crowns of the unerupted teeth. **4. ICC –** **IMAGING FEATURES** • **Internal Structure:** – Radiolucent • **Surrounding Structures:** – Tipping of involved molar so root tips are pushed into the lingual cortical plate of mandible and occlusal surface tipped toward buccal aspect – May displace and resorb adjacent teeth – May cause considerable amount of smooth expansion of the buccal cortical plate – If secondarily infected, periosteal new bone formation may be seen on the buccal cortex adjacent to involved tooth White & Pharoah, 2014 A B (a) Well-defined corticated lucent lesion (b) (c) Inflammatory periosteal response This border is sclerotic, related to the secondary infection Inflammatory effacement of the buccal cortex. This corresponds with the draining fistula Centred at the bifurcations. Note the tendency to extend distally (d) Slight flattening of the mandibular canal Koong, 2017  #### Internal Structure - Radiolucent #### Surrounding Structures - Tipping of involved molar so root tips are pushed into the lingual cortical plate of mandible and occlusal surface tipped toward buccal aspect - May displace and resorb adjacent teeth - May cause considerable amount of smooth expansion of the buccal cortical plate - If secondarily infected, periosteal new bone formation may be seen on the buccal cortex adjacent to involved tooth #### Figure Annotations (A, B) - (a) Well-defined corticated lucent lesion — centred at the bifurcations. Note the tendency to extend distally - (b) This border is sclerotic, related to the secondary infection - (c) Inflammatory periosteal response; inflammatory effacement of the buccal cortex. This corresponds with the draining fistula - (d) Slight flattening of the mandibular canal *White & Pharoah, 2014* *Koong, 2017* - ==Infection may produce layers of periosteal new bone, creating an onion-peel appearance==. - ==The tilted molar has more prominent, superiorly positioned lingual cusps, and CBCT demonstrates the tooth angulation and contact between the root apices and lingual cortical plate==. Composite radiographic images including a panoramic view (a) and cross-sectional CT scans (b, c, d) showing the imaging features of a lesion. Red leader lines connect specific anatomical findings to text labels describing them. # 4. ICC * **Histopathology:** * Resembles radicular cyst * **Treatment:** * Resolution without intervention * Curettage and enucleation * 3rd molars associated with PC are often removed * 1st and 2nd molars with MBBC can be conserved and erupt normally * **Recurrence:** * Does not recur This paradental cyst is composed of an inflamed fibrous wall lined by hyperplastic epithelium. The cyst appears as an open pocket. (WHO, 2022) **Essential diagnostic criteria:** 1. Associated with partially or recently erupted vital tooth 2. Radiolucency distinct from dental follicle 3. Intact lamina dura 4. Non keratinised epithelium  #### Histopathology - Resembles radicular cyst > This paradental cyst is composed of an inflamed fibrous wall lined by hyperplastic epithelium. The cyst appears as an open pocket. (WHO, 2022) #### Treatment - Resolution without intervention - Curettage and enucleation - 3rd molars associated with PC are often removed - 1st and 2nd molars with MBBC can be conserved and erupt normally #### Recurrence - Does not recur #### Essential Diagnostic Criteria 1. Associated with partially or recently erupted vital tooth 2. Radiolucency distinct from dental follicle 3. Intact lamina dura 4. Non keratinised epithelium A composite histopathology image showing a low-power view of an inflamed cyst wall (left) and a high-power view of the lining epithelium (right). The images illustrate the hyperplastic non-keratinised epithelium described in the diagnostic criteria. **5. NASOPALATINE DUCT CYST** * **Definition:** a developmental non-odontogenic cyst arising in the incisive canal. * **Related terminology:** Incisive canal cyst * **Epidemiology:** 5% of all cysts in the jaws; 80% of all non-odontogenic cysts * **Age:** 30-60 years * **Gender:** M>F; 3:1 - **Definition:** a developmental non-odontogenic cyst arising in the incisive canal. - **Related terminology:** Incisive canal cyst #### Epidemiology - 5% of all cysts in the jaws; 80% of all non-odontogenic cysts - **Age:** 30-60 years - **Gender:** M>F; 3:1 **5. NPDC** * **Aetiology:** – Arises from respiratory and squamous epithelial vestigial remnants of an embryonic nasopalatine duct present in some individuals – In one third of cases, inflammation from non-vital teeth or periodontal ligament may be a factor by stimulating the epithelial remnants to proliferate * **Clinical Features:** – Sessile swelling just posterior to maxillary incisors OR asymptomatic – May arise deeper and present as swelling on labial alveolus or bulging of nasal floor – Often traumatised and may become infected #### Aetiology - Arises from respiratory and squamous epithelial vestigial remnants of an embryonic nasopalatine duct present in some individuals - In one third of cases, inflammation from non-vital teeth or periodontal ligament may be a factor by stimulating the epithelial remnants to proliferate #### Clinical Features - Sessile swelling just posterior to maxillary incisors OR asymptomatic - May arise deeper and present as swelling on labial alveolus or bulging of nasal floor - Often traumatised and may become infected - ==A sessile swelling may be located at the incisive papilla.== **5. NPDC** * **Location:** – Found only in the midline of anterior hard palate – Between roots of incisors * **Periphery/Shape:** – Well-defined – Often corticated – May have characteristic heart shape – Size: incisive canal >6mm considered to be cyst (average diameter 18mm) * **Internal Structures:** – Radiolucency * **Surrounding Structures:** – Incisor roots may be displaced, but are vital – Lamina dura is intact White and Pharoah, 2014  #### Location - Found only in the midline of anterior hard palate - Between roots of incisors #### Periphery and Shape - Well-defined - Often corticated - May have characteristic heart shape - Size: incisive canal >6mm considered to be cyst (average diameter 18mm) #### Internal Structures - Radiolucency #### Surrounding Structures - Incisor roots may be displaced, but are vital - Lamina dura is intact *White and Pharoah, 2014* - ==The characteristic heart shape is particularly apparent on two-dimensional imaging.== A composite image of six periapical radiographs showing the anterior maxillary region, specifically focusing on the midline between the central incisors. The radiographs display a well-defined radiolucency in this area, consistent with the appearance of a Nasopalatine Duct Cyst (NPDC). Several images illustrate the characteristic heart-shaped border of the lesion caused by superimposition of the nasal spine. # 5. NPDC * **Histopathology:** – **Epithelium:** 90% lined by stratified squamous epithelium with focal areas of cuboidal, columnar, ciliated change * 50% of cases contain respiratory epithelium (but <10% are lined entirely by respiratory epithelium) – **Cyst wall:** Prominent neurovascular bundles with occasional small mucous glands or cartilage – Traumatised cysts are inflamed    - **Epithelium:** 90% lined by stratified squamous epithelium with focal areas of cuboidal, columnar, ciliated change - 50% of cases contain respiratory epithelium (but <10% are lined entirely by respiratory epithelium) - **Cyst wall:** Prominent neurovascular bundles with occasional small mucous glands or cartilage - Traumatised cysts are inflamed Clinical photo: A histopathological micrograph showing a cyst wall lined by a thin layer of epithelium overlying fibrous connective tissue. A histopathological micrograph showing a cyst lining composed of stratified squamous epithelium resting on a fibrous connective tissue wall. The image illustrates the characteristic epithelial changes described for Nasopalatine Duct Cysts, with multiple layers of cells and a prominent basement membrane. Histopathology slide showing a cyst wall lined by stratified epithelium overlying a fibrous connective tissue stroma. The image illustrates the variable lining described in the caption, appearing here as a multilayered (squamous) epithelium with underlying eosinophilic collagenous tissue. **5. NPDC** * **Treatment:** – Enucleation * **Recurrence:** – Do not normally recur <u>Essential diagnostic criteria:</u> 1. Epicentre at incisive canal 2. Lining of non-keratinised squamous or respiratory epithelium 3. +/- Neurovascular bundle in the cyst wall #### Treatment - Enucleation #### Recurrence - Do not normally recur #### Essential Diagnostic Criteria 1. Epicentre at incisive canal 2. Lining of non-keratinised squamous or respiratory epithelium 3. +/- Neurovascular bundle in the cyst wall **6. LATERAL PERIODONTAL AND BOTRYOID ODONTOGENIC CYST** * **Definition:** – Lateral periodontal cyst (LPC): a developmental odontogenic cyst lined by non-keratinized epithelium with characteristic thickenings. – Botryoid odontogenic cyst (BOC): a less common multilocular subtype of LPC. * **Epidemiology:** rare, <1% odontogenic cysts * **Age:** wide range, peak incidence 5th – 7th decades * **Gender:** slight male predilection #### Definition - **Lateral periodontal cyst (LPC):** a developmental odontogenic cyst lined by non-keratinized epithelium with characteristic thickenings. - **Botryoid odontogenic cyst (BOC):** a less common multilocular subtype of LPC. #### Epidemiology - Rare, <1% of odontogenic cysts - **Age:** wide range, peak incidence 5th–7th decades - **Gender:** slight male predilection - ==The lateral periodontal cyst and botryoid odontogenic cyst are considered the same lesion==. **6. LPC AND BOC** * **Aetiology:** – Unknown, thought to arise from odontogenic epithelial remnants, however source is controversial (either the dental lamina, reduced enamel epithelium, or epithelial rests of Malassez) * **Clinical Features:** – Asymptomatic in 90% of cases – Can mimic lateral periodontal abscess if secondarily infected – Expansion of buccal bone (50% of cases) – Usually small, (<1cm), but can attain considerable size #### Aetiology - Unknown; thought to arise from odontogenic epithelial remnants, however the source is controversial (either the dental lamina, reduced enamel epithelium, or epithelial rests of Malassez) #### Clinical Features - Asymptomatic in 90% of cases - Can mimic a lateral periodontal abscess if secondarily infected - Expansion of buccal bone (50% of cases) - Usually small (<1 cm), but can attain considerable size - ==Botryoid odontogenic cysts may become much larger==. **6. LPC AND BOC – IMAGING FEATURES** • **Location:** – Mandible > Maxilla – Anterior to molars (particularly premolar region) – Multifocal occurrence has been reported – Centred upon lateral surface of root • **Periphery/Shape:** – Well-defined with prominent cortical boundary – Round/oval shape – LPC: unilocular – BOC: multilocular White and Pharoah, 2014    #### Location - Mandible > Maxilla - Anterior to molars (particularly premolar region) - Multifocal occurrence has been reported - Centred upon the lateral surface of the root #### Periphery and Shape - Well-defined with prominent cortical boundary - Round/oval shape - LPC: unilocular - BOC: multilocular *White and Pharoah, 2014* A dental radiograph showing the roots of posterior teeth with restorations. A well-defined, round radiolucency with a prominent white cortical border is visible adjacent to the root surface in the lower jaw. Radiograph: A panoramic dental X-ray showing the maxilla and mandible with multiple teeth, including several restorations. In the lower right quadrant (patient's left), a radiolucent lesion is visible in the bone beneath the premolar/molar region. Radiographic cross-section (axial CT slice) of the mandible showing a well-defined, multilocular radiolucent lesion in the anterior region. The image illustrates the cortical boundary and internal septa characteristic of buccal bifurcation cysts or lateral periodontal cysts as described in the accompanying text. # 6. LPC AND BOC – IMAGING FEATURES * **Internal Structure:** * Radiolucent * BOC may have multilocular appearance (related more to histologic appearance) * **Surrounding Structures:** * Small cysts may efface the lamina dura of adjacent roots (but tooth roots are rarely resorbed) * Large cysts may displace adjacent teeth and cause expansion * May have similar growth pattern to OKCs with minimum expansion of the involved bone WHO, 2022   #### Internal Structure - Radiolucent - BOC may have a multilocular appearance (related more to histologic appearance) #### Surrounding Structures - Small cysts may efface the lamina dura of adjacent roots (but tooth roots are rarely resorbed) - Large cysts may displace adjacent teeth and cause expansion - May have a similar growth pattern to OKCs with minimum expansion of the involved bone *WHO, 2022* - ==Botryoid odontogenic cysts contain multiple separate locules and internal septa==. Radiograph: A dental X-ray showing a well-defined radiolucent lesion in the jawbone, illustrating the internal structure of a cyst as described in the slide text. Radiograph: A cropped dental X-ray showing a radiolucent lesion with a scalloped, multilocular appearance located between tooth roots in the anterior jaw. # 6. LPC AND BOC * **Histopathology:** * **Epithelium:** thin, non-keratinised squamous or cuboidal epithelium 1-3 cells thick with focal, whorled, plaque-like epithelial thickenings * **Cyst wall:** uninflamed fibrous wall * BOC: same appearance, but multicystic spaces WHO classification of head and neck tumours, 2017   #### Histopathology - **Epithelium:** thin, non-keratinised squamous or cuboidal epithelium 1–3 cells thick with focal, whorled, plaque-like epithelial thickenings - **Cyst wall:** uninflamed fibrous wall - **BOC:** same appearance, but with multicystic spaces *WHO classification of head and neck tumours, 2017* Histopathology micrograph showing cystic spaces lined by a thin, non-keratinised epithelium (indicated by the upper yellow arrow) and a distinct focal, whorled, plaque-like epithelial thickening (indicated by the lower yellow arrow). The wall appears uninflamed. A photomicrograph of a histological section showing multiple cystic spaces separated by fibrous connective tissue septa. The lining epithelium is thin and non-keratinised, appearing as a delicate purple layer surrounding the clear luminal areas. **6. LPC AND BOC** * **Treatment:** – Enucleation, without removal of adjacent tooth/teeth * **Recurrence:** – Rare for simple unilocular cysts – Approx 22% for BOCs * Likely due to multicystic nature of the lesion <u>**Essential diagnostic criteria:**</u> 1. Located in on lateral aspect or between the roots of vital erupted teeth 2. Characteristic whorled epithelial plaques 3. Multilocular (BOC only) #### Treatment - Enucleation, without removal of the adjacent tooth/teeth #### Recurrence - Rare for simple unilocular cysts - Approximately 22% for BOCs - Likely due to the multicystic nature of the lesion #### Essential Diagnostic Criteria 1. Located on the lateral aspect or between the roots of vital erupted teeth 2. Characteristic whorled epithelial plaques 3. Multilocular (BOC only) # 7. SURGICAL CILIATED CYST * **Definition:** a benign cyst caused by the traumatic implantation, usually surgical, of respiratory epithelium in the gnathic bones. * **Related terminology:** – Acceptable: surgical ciliated cyst of the maxilla; postoperative maxillary cyst (if maxillary location); (Respiratory) implantation cyst * **Epidemiology:** rare * **Age:** 5th to 6th decade * **Gender:** no gender predilection WHO, 2022  - **Definition:** a benign cyst caused by the traumatic implantation, usually surgical, of respiratory epithelium in the gnathic bones. - **Related terminology:** - Acceptable: surgical ciliated cyst of the maxilla; postoperative maxillary cyst (if maxillary location); (Respiratory) implantation cyst - **Epidemiology:** rare - **Age:** 5th to 6th decade - **Gender:** no gender predilection *WHO, 2022* Radiograph: A coronal computed tomography (CT) scan of the maxillary sinus region showing a well-defined, rounded radiolucency located in the floor of the maxillary sinus. The image also displays dental implants or restorations with significant radiopacity at the bottom of the frame. **7. SURGICAL CILIATED CYST** * **Aetiology:** – Cysts develop from entrapped sinus or nasal mucosa in the jaw bones following trauma or surgery (e.g. Calwell-Luc or Le Fort I procedures, sinus surgery, maxillary fracture, midface osteotomy, or traumatic tooth extraction) – Mandibular cases are generally caused by implantation of sinus epithelium by contaminated instruments, or, transfer of epithelium with autologous nasal osteocartilagenous grafts for chin augmentation – The cyst usually develops after a long latent period, the reported delay being up to 20 years after the causative surgery. It is thought that the cyst cavity forms due to persistent mucous secretion. * **Clinical Features:** – May be asymptomatic or present with swelling, pain, or tenderness - **Aetiology:** - Cysts develop from entrapped sinus or nasal mucosa in the jaw bones following trauma or surgery (e.g. Calwell-Luc or Le Fort I procedures, sinus surgery, maxillary fracture, midface osteotomy, or traumatic tooth extraction) - Mandibular cases are generally caused by implantation of sinus epithelium by contaminated instruments, or, transfer of epithelium with autologous nasal osteocartilagenous grafts for chin augmentation - The cyst usually develops after a long latent period, the reported delay being up to 20 years after the causative surgery. It is thought that the cyst cavity forms due to persistent mucous secretion. - **Clinical Features:** - May be asymptomatic or present with swelling, pain, or tenderness **7. SURGICAL CILIATED CYST** • **Location:** – The gnathic bones, most common in posterior maxilla – Very rare in the mandible • **Radiographic features:** – Radiographs show a well-demarcated unilocular radiolucency of the jaws. – Approximately 60% of cases are at least partially surrounded by a corticated margin. – Occasional large lesions in the maxilla may fill the sinus or be multilocular  - **Location:** - The gnathic bones, most common in posterior maxilla - Very rare in the mandible - **Radiographic features:** - Radiographs show a well-demarcated unilocular radiolucency of the jaws. - Approximately 60% of cases are at least partially surrounded by a corticated margin. - Occasional large lesions in the maxilla may fill the sinus or be multilocular - ==Surgical plates may provide evidence of previous surgery.== A panoramic radiograph of the maxilla and mandible showing a full set of teeth with extensive dental restorations, including multiple bright white metallic plates and screws used for fixation along the jaw lines. # 7. SURGICAL CILIATED CYST * **Histopathology:** * **Epithelium:** Pseudostratified ciliated columnar respiratory epithelium * +/- squamous metaplasia or simple cuboidal cells * +/- mucous (goblet) cells * **Cyst wall:** loose fibrous connective tissue, which may be inflamed * +/- subepithelial fibrosis or hyalinisation * **Treatment:** * Simple enucleation * **Recurrence:** * Rare **Essential diagnostic criteria:** 1. A history of previous surgery 2. Radiolucent well demarcated cyst 3. Respiratory epithelial lining  - **Histopathology:** - **Epithelium:** pseudostratified ciliated columnar respiratory epithelium - +/- squamous metaplasia or simple cuboidal cells - +/- mucous (goblet) cells - **Cyst wall:** loose fibrous connective tissue, which may be inflamed - +/- subepithelial fibrosis or hyalinisation - **Treatment:** - Simple enucleation - **Recurrence:** - Rare #### Essential Diagnostic Criteria 1. A history of previous surgery 2. Radiolucent well demarcated cyst 3. Respiratory epithelial lining 4. A history of previous surgery or ==trauma in the region== - ==Removal of the cyst lining== Histological micrograph showing a cyst wall lined by a bilaminar layer of cuboidal epithelial cells with focal cilia on the luminal surface, resting on a loose fibrous connective tissue stroma. **8. ORTHOKERATINISED ODONTOGENIC CYST** * **Definition:** a developmental cyst lined by orthokeratinised stratified squamous epithelium * **Related terminology:** * Not recommended: Orthokeratinized variant of odontogenic keratocyst * **Epidemiology:** rare (<1% of odontogenic cysts) * **Age:** wide range, average age 35 years; peak incidence in 3^rd – 4^th decades * **Gender:** 65% occur in males - **Definition:** a developmental cyst lined by orthokeratinised stratified squamous epithelium - **Related terminology:** - Not recommended: Orthokeratinized variant of odontogenic keratocyst - **Epidemiology:** rare (<1% of odontogenic cysts) - **Age:** wide range, average age 35 years; peak incidence in 3rd – 4th decades - **Gender:** 65% occur in males - ==It is now considered a separate entity==. **8. OOC** • **Aetiology:** – Unknown, but most likely arises from the remnants of dental lamina • **Clinical Features:** – Painless swelling, but many are incidental findings during radiographic examination – Rare cases of multiple or bilateral OOC have been reported, but no evidence of association with Gorlin Syndrome (naevoid basal cell carcinoma) - **Aetiology:** - Unknown, but most likely arises from the remnants of dental lamina - **Clinical Features:** - Painless swelling, but many are incidental findings during radiographic examination - Rare cases of multiple or bilateral OOC have been reported, but no evidence of association with Gorlin Syndrome (naevoid basal cell carcinoma) # 8. OOC * **Location:** – Mandible (80%) * 65% in angle/ramus region * **Radiographic features:** – Well-demarcated, spherical unilocular radiolucent lesions, often with a corticated margin – Occasional cases (<10%) are multilocular – Up to 70% of all lesions are associated with an impacted tooth, with a radiological similarity to dentigerous cysts WHO, 2022  - **Location:** - Mandible (80%) - 65% in angle/ramus region - **Radiographic features:** - Well-demarcated, spherical unilocular radiolucent lesions, often with a corticated margin - Occasional cases (<10%) are multilocular - Up to 70% of all lesions are associated with an impacted tooth, with a radiological similarity to dentigerous cysts *WHO, 2022* A dental radiograph showing the posterior mandible with a large, well-defined radiolucent lesion surrounding the crown of an impacted tooth. 8. OOC • Histopathology: – Epithelium: thin regular orthokeratinized stratified squamous epithelium with a prominent granular cell layer and inconspicuous or low cuboidal basal cells. It is heavily keratinized, often with lamellae of keratin filling the lumen – Cyst wall: fibrous and may show areas of inflammation • +/- parakeratinized or non-keratinized areas, but these form a small part of the lining and are often associated with inflammation • Rare examples include sebaceous glands in the lining • Microcysts may be seen in the wall in 5% of cases • Treatment: – Enucleation • Recurrence: – Rare (less than 5%) Essential diagnostic criteria: 1. Located in tooth bearing areas of jaw 2. Thin, regular epithelial lining with orthokeratinization  - **Histopathology:** - Epithelium: thin regular orthokeratinized stratified squamous epithelium with a prominent granular cell layer and inconspicuous or low cuboidal basal cells. It is heavily keratinized, often with lamellae of keratin filling the lumen - Cyst wall: fibrous and may show areas of inflammation - +/- parakeratinized or non-keratinized areas, but these form a small part of the lining and are often associated with inflammation - Rare examples include sebaceous glands in the lining - Microcysts may be seen in the wall in 5% of cases - **Treatment:** - Enucleation - **Recurrence:** - Rare (less than 5%) **Essential diagnostic criteria:** 1. Located in tooth bearing areas of jaw 2. Thin, regular epithelial lining with orthokeratinization - ==The keratinised layer lacks cell nuclei==. - ==Enucleation includes removal of the cyst lining==. A histological micrograph showing a cyst lining composed of thin, regular stratified squamous epithelium. The surface exhibits prominent orthokeratinization with wavy, lamellated keratin layers that separate and extend into the empty space of the lumen. <h2>9. CALCIFYING ODONTOGENIC CYST</h2> <ul> <li><b>Definition:</b> A developmental odontogenic cyst characterized histologically by ghost cells, which often calcify.</li> <li><b>Related terminology:</b> calcifying cystic odontogenic tumour, Gorlin cyst</li> <li><b>Epidemiology:</b> rare, &lt;1% odontogenic cysts</li> <li><b>Age:</b> peak incidence 2^nd – 3^rd decade</li> <li><b>Gender:</b> no gender predilection</li> </ul> - **Definition:** A developmental odontogenic cyst characterized histologically by ghost cells, which often calcify. - **Related terminology:** calcifying cystic odontogenic tumour, Gorlin cyst - **Epidemiology:** rare, <1% of odontogenic cysts - **Age:** peak incidence 2nd – 3rd decade - **Gender:** no gender predilection - ==It occupies a spectrum from a cystic lesion to a solid odontogenic neoplasm.== **9. COC** * **Aetiology:** – Unknown – Has mutations in CTNNB1 gene which implicate the Wnt pathway. This pathway is also involved in odontomas, with which COC is often associated. * **Clinical Features:** – Asymptomatic in most cases – Painless swelling of jaws – Extraosseous lesions present as gingival swellings, sometimes with pain and tenderness #### Aetiology - Unknown - Has mutations in the CTNNB1 gene which implicate the Wnt pathway. This pathway is also involved in odontomas, with which COC is often associated. #### Clinical Features - Asymptomatic in most cases - Painless swelling of jaws - Extraosseous lesions present as gingival swellings, sometimes with pain and tenderness # 9. COC – IMAGING FEATURES * **Location:** * Maxilla = Mandible * Anterior > Posterior (esp. with cuspids and incisors) * Association with odontomas (more common in maxilla) * Central > Peripheral * Up to 10% are extraosseous (anterior regions of jaw) * **Periphery/Shape:** * Variable * Well-defined, corticated with curved, cyst-like shape * Ill-defined and irregular White and Pharoah, 2014   #### Location - Maxilla = mandible - Anterior > posterior (especially with cuspids and incisors) - Association with odontomas (more common in maxilla) - Central > peripheral - Up to 10% are extraosseous (anterior regions of jaw) #### Periphery and Shape - Variable - Well-defined, corticated with curved, cyst-like shape - Ill-defined and irregular *White and Pharoah, 2014* A dental radiograph showing a large, mixed-density lesion in the anterior jaw region. The lesion contains central radiopaque structures resembling tooth material (consistent with an odontoma) surrounded by a radiolucent area that appears well-defined and corticated. A periapical radiograph showing a large, well-defined radiolucent lesion in the anterior maxilla associated with an unerupted tooth. The lesion contains multiple small, irregular radiopaque foci (calcifications) within its lower aspect. **9. COC – IMAGING FEATURES** • **Internal Structure:** – Variable • Completely radiolucent • Evidence of small foci of calcified material – white flecks or small smooth pebbles • Larger, solid, amorphous masses • Rarely appear multilocular • **Surrounding Structures:** – Impedes eruption of associated tooth – Tooth displacement and root resorption – Expansion and perforation of cortical plates WHO, 2022  #### Internal Structure - Variable: - Completely radiolucent - Evidence of small foci of calcified material – white flecks or small smooth pebbles - Larger, solid, amorphous masses - Rarely appear multilocular #### Surrounding Structures - Impedes eruption of associated tooth - Tooth displacement and root resorption - Expansion and perforation of cortical plates *WHO, 2022* Radiograph: A lateral jaw X-ray showing a large radiolucent lesion in the posterior mandible containing multiple small, distinct radiopaque foci resembling 'white flecks' or 'pebbles'. An impacted tooth is displaced inferiorly by the lesion. # 9. COC * **Histopathology:** – Unilocular cyst – **Epithelium:** stratified epithelial lining of varying thickness resembling stellate reticulum and with palisaded and hyperchromatic columnar ameloblast-like basal cells. * + <u>Ghosts cells are characteristic</u> – Rounded or stacked flattened pale eosinophilic cells within the epithelium with distinct outlines and karyolysis resulting in a 'ghost like appearance’ – Variable in number and often pass into the connective tissue of the cyst wall, eliciting a foreign body reaction and inducing dentinoid. – Although characteristic, ghost cells also occur in other odontogenic tumours and do not alone justify a diagnosis of COC * +/- intraluminal and/or mural epithelial proliferation producing ameloblastoma-like areas   #### Histopathology - Unilocular cyst - **Epithelium:** stratified epithelial lining of varying thickness resembling stellate reticulum and with palisaded and hyperchromatic columnar ameloblast-like basal cells. - **Ghost cells are characteristic:** - Rounded or stacked flattened pale eosinophilic cells within the epithelium with distinct outlines and karyolysis resulting in a 'ghost-like appearance' - Variable in number and often pass into the connective tissue of the cyst wall, eliciting a foreign body reaction and inducing dentinoid - Although characteristic, ghost cells also occur in other odontogenic tumours and do not alone justify a diagnosis of COC - +/- intraluminal and/or mural epithelial proliferation producing ameloblastoma-like areas - ==Ghost cells lack nuclei but retain the cell outline.== Histopathology slide showing clusters of ghost cells, which appear as pale pink, rounded structures with distinct outlines but lacking nuclei (karyolysis). These are embedded within a background of darker purple connective tissue and epithelial cells. Histopathology slide showing a cystic lesion lined by stratified epithelium with prominent basal cells and numerous homogeneous eosinophilic ghost cells. An orange arrow points to the region of ghost cell accumulation within the epithelial lining. **9. COC** * **Treatment:** – Conservative surgical removal, enucleation and/or curettage * **Recurrence:** – Post-tx follow up required – 8% recurrence rate <u>**Essential diagnostic criteria:**</u> 1. Cystic architecture 2. Numerous ghost cells #### Treatment - Conservative surgical removal, enucleation and/or curettage #### Recurrence - Post-treatment follow-up required - 8% recurrence rate #### Essential Diagnostic Criteria 1. Cystic architecture 2. Numerous ghost cells **10. GLANDULAR ODONTOGENIC CYST** * **Definition:** a developmental cyst in which the epithelial lining resembles glandular tissue. * **Related terminology:** – Not recommended: sialo-odontogenic cyst; mucoepidermoid odontogenic cyst * **Epidemiology:** rare, <0.5% odontogenic cysts * **Age:** average age = 50 years, peak incidence 5th – 7th decades * **Gender:** no gender predilection - **Definition:** a developmental cyst in which the epithelial lining resembles glandular tissue. - **Related terminology:** - Not recommended: sialo-odontogenic cyst; mucoepidermoid odontogenic cyst - **Epidemiology:** rare, <0.5% of odontogenic cysts - **Age:** average age = 50 years, peak incidence 5th–7th decades - **Gender:** no gender predilection > [!note] Lecturer — Terminology Clarification > The previous names are not recommended because they can be confused with other entities. **10. GOC** * **Aetiology:** – Unknown – Thought to arise from remnants of dental lamina * **Clinical Features:** – Slowly expanding, painless swelling – Association with impacted tooth is extremely rare – Mandibular lesions may reach a large size and cross the midline - **Aetiology:** - Unknown - Thought to arise from remnants of the dental lamina - **Clinical Features:** - Slowly expanding, painless swelling - Association with an impacted tooth is extremely rare - Mandibular lesions may reach a large size and cross the midline **10. GOC – IMAGING FEATURES** White and Pharoah, 2014 * **Location:** – Exclusively in the jaws – Mandible > Maxilla – Anterior > Posterior * **Periphery/Shape:** – Well-defined cortical boundary – Smooth or scalloped * **Internal Structure:** – Unilocular or multilocular * **Surrounding Structures:** – Expansion of outer cortical plate of jaws * Regions of perforation – Displacement +/- resorption (25%) of teeth  *White and Pharoah, 2014* - **Location:** - Exclusively in the jaws - Mandible > Maxilla - Anterior > Posterior - **Periphery/Shape:** - Well-defined cortical boundary - Smooth or scalloped - **Internal Structure:** - Unilocular or multilocular - **Surrounding Structures:** - Expansion of the outer cortical plate of the jaws - Regions of perforation - Displacement ± resorption (25%) of teeth - ==Cortical thinning may also occur.== Radiograph: Two dental imaging panels (A and B) illustrating the features of a glandular odontogenic cyst. Panel A is an anterior mandibular occlusal radiograph showing a multilocular radiolucency with scalloped borders in the symphysis region. Panel B is an axial CT scan demonstrating expansion of the cortical plates and perforation by the lesion. # 10. GOC * **Histopathology:** – Often multilocular cysts – Epithelium: of variable thickness, ranging from a thin layer of flattened squamous or cuboidal cells to stratified squamous epithelium * + Hobnail cells in all cases (Cuboidal or low columnar cells on the luminal surface) * +/- whorled epithelial thickenings, or plaques similar to those in lateral periodontal cyst. * +/- intraepithelial microcysts, apocrine metaplasia, clear cells, papillary projections (tufting), cilia and mucous cells * (Not all features are present in every case and a higher number of features allows more confident diagnosis)   - **Histopathology:** - Often multilocular cysts - Epithelium: of variable thickness, ranging from a thin layer of flattened squamous or cuboidal cells to stratified squamous epithelium - + Hobnail cells in all cases (cuboidal or low columnar cells on the luminal surface) - ± whorled epithelial thickenings, or plaques similar to those in the lateral periodontal cyst - ± intraepithelial microcysts, apocrine metaplasia, clear cells, papillary projections (tufting), cilia and mucous cells > Not all features are present in every case, and a higher number of features allows a more confident diagnosis. - ==Previously, diagnosis was based on the presence of seven of ten specified criteria.== Histopathology micrograph showing an epithelial lining with intraepithelial microcysts and duct-like structures, along with a superficial layer of columnar cells. Histopathology: Microscopic section showing an epithelial lining with distinct whorled thickenings (plaques) and papillary projections extending into the cystic space. The superficial layer consists of columnar cells, set against a fibrous connective tissue wall. **10. GOC** * **Treatment:** – Enucleation – Resection has been advocated due to high recurrence * particularly for large or multilocular lesions * **Recurrence:** – Recur in 22% of cases after enucleation (esp. large and multilocular lesions) – Post-tx radiological review – May occur up to 8 years later <u>**Essential diagnostic criteria:**</u> 1. Radiolucent cystic lesion of tooth-bearing area of the jaw 2. Often multilocular 3. Lining of variable thickness with epithelial thickening, plaques or papillary projections + Hobnail cells +/- microcysts or duct-like structures +/- mucous or clear cells. - **Treatment:** - Enucleation - Resection has been advocated due to high recurrence, particularly for large or multilocular lesions - **Recurrence:** - Recurs in 22% of cases after enucleation (especially large and multilocular lesions) - Post-treatment radiological review - May occur up to 8 years later #### Essential Diagnostic Criteria 1. Radiolucent cystic lesion of the tooth-bearing area of the jaw 2. Often multilocular 3. Lining of variable thickness with epithelial thickening, plaques or papillary projections + Hobnail cells ± microcysts or duct-like structures ± mucous or clear cells - ==Removal of the cyst lining is usually performed with enucleation.== - ==Radiological review is required for at least eight years.== **REFERENCES** * Cawson, R.A, and Odell, E.W. (2008). *Cawson's Essentials of Oral Pathology and Oral Medicine E-Book* (8th ed.). Churchill Livingstone. * WHO Classification of Tumours Editorial Board. Head and neck tumours. Lyon (France): International Agency for Research on Cancer; 2022 (WHO classification of tumours series, 5th ed.; vol. 9). * Koong, B. (2017). *Atlas of Oral and Maxillofacial Radiology*. Chichester, UK: John Wiley and Sons. * White, and Pharoah. (2014). *Oral radiology : Principles and interpretation* (7^th ed.). St. Louis: Elsevier/Mosby. - *Cawson, R.A., and Odell, E.W. (2008). Cawson's Essentials of Oral Pathology and Oral Medicine E-Book (8th ed.). Churchill Livingstone.* - *WHO Classification of Tumours Editorial Board. Head and neck tumours. Lyon (France): International Agency for Research on Cancer; 2022 (WHO classification of tumours series, 5th ed.; vol. 9).* - *Koong, B. (2017). Atlas of Oral and Maxillofacial Radiology. Chichester, UK: John Wiley and Sons.* - *White, and Pharoah. (2014). Oral radiology: Principles and interpretation (7th ed.). St. Louis: Elsevier/Mosby.* ## Case: Cyst with a corticated border ### Question **Scenario:** A radiograph of a jaw cyst is presented to illustrate its border characteristics. **What's shown:** A well-defined radiolucent lesion surrounded by a thin, uniform radiopaque line. **Consider:** Identify the specific border feature shown and explain what it indicates about the cyst. ### Answer **Observations:** - A thin, uniform radiopaque line surrounding the radiolucent cyst. **Reasoning:** This thin, uniform radiopaque line represents a corticated border. Most cysts of the jaws are well-defined and exhibit this characteristic corticated margin, indicating a slow-growing, benign process that allows the surrounding bone to form a distinct boundary. **Takeaway:** Most cysts of the jaws are well-defined and corticated, presenting with a thin, uniform radiopaque border. ## Case: Long-standing cyst with dystrophic calcification and septa ### Question **Scenario:** A radiograph of a long-standing jaw cyst is presented to demonstrate internal changes over time. **What's shown:** A radiolucent lesion containing sparse, opaque, dotty appearances and thin opaque lines crossing through it. **Consider:** Identify the internal features shown and explain what they indicate about the duration and structure of the cyst. ### Answer **Observations:** - Sparse, opaque, dotty radiopacities within the radiolucency. - Thin opaque lines traversing the cyst. **Reasoning:** The sparse, opaque, dotty appearances represent dystrophic calcifications, which can occur in cysts that have been present for a long time. The thin opaque lines represent septa within the cyst itself. **Takeaway:** Long-standing cysts may demonstrate internal dystrophic calcifications and septa, appearing as sparse radiopacities and thin opaque lines on radiographs. ## Case: Dentigerous cyst causing displacement of developing teeth 47 and 4 ### Question **Scenario:** A radiograph is presented showing a dentigerous cyst in the mandible. **What's shown:** A radiolucent lesion associated with an unerupted tooth, causing positional changes to adjacent developing teeth. **Consider:** Identify the positional changes of the developing teeth and explain the mechanism. ### Answer **Observations:** - Displacement of the developing tooth 47. - Mesial displacement of the developing tooth 4. **Reasoning:** The expanding dentigerous cyst occupies space within the jaw, physically pushing the adjacent developing teeth out of their normal eruption paths, resulting in displacement. **Takeaway:** Dentigerous cysts can cause significant displacement of adjacent developing teeth due to their space-occupying mass effect. ## Case: Cyst causing displacement of tooth 37 ### Question **Scenario:** A radiograph is presented showing a cyst in the mandible affecting the adjacent teeth. **What's shown:** A radiolucent lesion located between teeth 37 and 36, with tooth 37 positioned at a noticeably different angle compared to the contralateral tooth 47. **Consider:** Identify the effect the cyst is having on tooth 37 and explain the mechanism behind this change. ### Answer **Observations:** - Tooth 37 is angled differently from the contralateral tooth 47. - The cyst is occupying space between teeth 37 and 36. **Reasoning:** The cyst is acting as a space-occupying lesion. By taking up space between the teeth, it physically pushes tooth 37 posteriorly, altering its angle and position. **Takeaway:** Cysts of the jaws can cause mass effect features, including the displacement and resorption of adjacent teeth due to space occupation. ## Case: Cyst with a corticated border ### Question **Scenario:** A radiograph of a jaw cyst is presented to illustrate its border characteristics. **What's shown:** A well-defined radiolucent lesion surrounded by a thin, uniform radiopaque line. **Consider:** Identify the specific border feature shown and explain what it indicates about the cyst.  ### Answer **Observations:** - A thin, uniform radiopaque line surrounding the radiolucent cyst. **Reasoning:** This thin, uniform radiopaque line represents a corticated border. Most cysts of the jaws are well-defined and exhibit this characteristic corticated margin, indicating a slow-growing, benign process that allows the surrounding bone to form a distinct boundary. **Takeaway:** Most cysts of the jaws are well-defined and corticated, presenting with a thin, uniform radiopaque border. ## Case: Long-standing cyst with dystrophic calcification and septa ### Question **Scenario:** A radiograph of a long-standing jaw cyst is presented to demonstrate internal changes over time. **What's shown:** A radiolucent lesion containing sparse, opaque, dotty appearances and thin opaque lines crossing through it. **Consider:** Identify the internal features shown and explain what they indicate about the duration and structure of the cyst.   ### Answer **Observations:** - Sparse, opaque, dotty radiopacities within the radiolucency. - Thin opaque lines traversing the cyst. **Reasoning:** The sparse, opaque, dotty appearances represent dystrophic calcifications, which can occur in cysts that have been present for a long time. The thin opaque lines represent septa within the cyst itself. **Takeaway:** Long-standing cysts may demonstrate internal dystrophic calcifications and septa, appearing as sparse radiopacities and thin opaque lines on radiographs. ## Case: Dentigerous cyst causing displacement of developing teeth 47 and 4 ### Question **Scenario:** A radiograph is presented showing a dentigerous cyst in the mandible. **What's shown:** A radiolucent lesion associated with an unerupted tooth, causing positional changes to adjacent developing teeth. **Consider:** Identify the positional changes of the developing teeth and explain the mechanism.  ### Answer **Observations:** - Displacement of the developing tooth 47. - Mesial displacement of the developing tooth 4. **Reasoning:** The expanding dentigerous cyst occupies space within the jaw, physically pushing the adjacent developing teeth out of their normal eruption paths, resulting in displacement. **Takeaway:** Dentigerous cysts can cause significant displacement of adjacent developing teeth due to their space-occupying mass effect. ## Case: Cyst causing displacement of tooth 37 ### Question **Scenario:** A radiograph is presented showing a cyst in the mandible affecting the adjacent teeth. **What's shown:** A radiolucent lesion located between teeth 37 and 36, with tooth 37 positioned at a noticeably different angle compared to the contralateral tooth 47. **Consider:** Identify the effect the cyst is having on tooth 37 and explain the mechanism behind this change.  ### Answer **Observations:** - Tooth 37 is angled differently from the contralateral tooth 47. - The cyst is occupying space between teeth 37 and 36. **Reasoning:** The cyst is acting as a space-occupying lesion. By taking up space between the teeth, it physically pushes tooth 37 posteriorly, altering its angle and position. **Takeaway:** Cysts of the jaws can cause mass effect features, including the displacement and resorption of adjacent teeth due to space occupation. Case: Cyst with a corticated border Radiograph: A dental X-ray of the mandible showing a well-defined, corticated radiolucent lesion located below the roots of the teeth. Three black arrows point to the distinct borders of this spherical lesion, illustrating the general imaging features described. Radiograph: A dental X-ray showing the lower jaw with teeth, highlighting a large radiolucent area (cyst) indicated by black arrows. The image illustrates the displacement of tooth roots and the inferior alveolar canal caused by the lesion. A panoramic dental radiograph showing the full dentition and jaws. White arrows point to a large, well-defined radiolucent area in the left posterior mandible (patient's left) that has caused expansion and thinning of the inferior cortical border. B Radiograph: A cropped dental radiograph (likely a panoramic or periapical view) showing a large, well-defined radiolucent lesion in the jaw. The lesion surrounds the crown of an impacted tooth located in the upper right quadrant, consistent with the imaging features described for a dentigerous cyst. A panoramic dental radiograph showing the full dentition and jaws. White arrows point to a large, well-defined radiolucent area in the left posterior mandible (patient's left) that has caused expansion and thinning of the inferior cortical border. ## Case: Cyst causing inferior displacement of the inferior alveolar canal ### Question **Scenario:** A radiograph is presented showing a cyst in the mandible affecting the inferior alveolar canal. **What's shown:** A radiolucent lesion in the mandible with the inferior alveolar canal pushed inferiorly, compared to the contralateral side where it is located much closer to the apices of the teeth. **Consider:** Identify the effect of the cyst on the inferior alveolar canal and explain how this is determined. ### Answer **Observations:** - The inferior alveolar canal is displaced inferiorly on the affected side. - The contralateral canal is in its normal, more superior position near the tooth apices. **Reasoning:** The cyst exerts a mass effect, occupying space within the mandible and physically pushing the inferior alveolar canal in an inferior direction. Comparing it to the normal contralateral side confirms the displacement. **Takeaway:** Displacement of the inferior alveolar canal is a mass effect feature of jaw cysts, often pushed inferiorly by the expanding lesion. ## Case: Residual radicular cyst after tooth extraction ### Question **Scenario:** A radiograph is presented showing a cystic lesion in an edentulous area. **What's shown:** A well-defined radiolucent lesion in the jaw where a tooth has previously been extracted. **Consider:** Identify the anatomical context of this radiolucency and explain how it differs from a standard radicular cyst. ### Answer **Observations:** - A cystic lesion is present in an area where the associated tooth has been removed. **Reasoning:** Normally, a radicular cyst requires a non-vital tooth to be present. In this case, the tooth was extracted, but the cystic epithelium was left behind, allowing the cyst to continue growing as a residual radicular cyst. **Takeaway:** A residual radicular cyst occurs when cystic epithelium is left behind after the extraction of a non-vital tooth, allowing the cyst to persist and grow. ## Case: Radicular cyst centered at the tooth apex ### Question **Scenario:** Radiographs of radicular cysts are presented to demonstrate their typical location. **What's shown:** Radiolucent lesions centered directly over the apical foramen of non-vital teeth. **Consider:** Identify the epicenter of the radiolucency in relation to the tooth and explain its clinical significance. ### Answer **Observations:** - The center of the cystic lesion is located around the apex of the involved tooth. **Reasoning:** Radicular cysts arise from chronic inflammation at the apex of a non-vital tooth. Consequently, the epicenter of the radiolucency is generally centered over the apical foramen, unless it arises from a lateral canal. **Takeaway:** A radicular cyst is typically centered around the apex of a non-vital tooth, reflecting its inflammatory origin at the apical foramen. ## Case: Radicular cyst extending into the maxillary sinus ### Question **Scenario:** A radiograph is presented showing a radicular cyst in the posterior maxilla. **What's shown:** A radiolucent lesion extending into the maxillary sinus, with the buccal plate expanded into a curved, circular shape and appearing very thin. **Consider:** Describe the effect of the lesion on the adjacent anatomical structures and the cortical bone. ### Answer **Observations:** - The cyst extends into the maxillary sinus, elevating the sinus floor. - The buccal cortical plate is expanded, thinned, and curved. **Reasoning:** As a space-occupying lesion, the radicular cyst expands into the path of least resistance. It can extend into the maxillary sinus while keeping the sinus floor intact, and it causes significant thinning and expansion of the buccal cortical plate. **Takeaway:** Radicular cysts can extend into the maxillary sinus and cause significant expansion and thinning of the buccal cortical plate. ## Case: Cyst causing inferior displacement of the inferior alveolar canal ### Question **Scenario:** A radiograph is presented showing a cyst in the mandible affecting the inferior alveolar canal. **What's shown:** A radiolucent lesion in the mandible with the inferior alveolar canal pushed inferiorly, compared to the contralateral side where it is located much closer to the apices of the teeth. **Consider:** Identify the effect of the cyst on the inferior alveolar canal and explain how this is determined.  ### Answer **Observations:** - The inferior alveolar canal is displaced inferiorly on the affected side. - The contralateral canal is in its normal, more superior position near the tooth apices. **Reasoning:** The cyst exerts a mass effect, occupying space within the mandible and physically pushing the inferior alveolar canal in an inferior direction. Comparing it to the normal contralateral side confirms the displacement. **Takeaway:** Displacement of the inferior alveolar canal is a mass effect feature of jaw cysts, often pushed inferiorly by the expanding lesion. ## Case: Residual radicular cyst after tooth extraction ### Question **Scenario:** A radiograph is presented showing a cystic lesion in an edentulous area. **What's shown:** A well-defined radiolucent lesion in the jaw where a tooth has previously been extracted. **Consider:** Identify the anatomical context of this radiolucency and explain how it differs from a standard radicular cyst.   ### Answer **Observations:** - A cystic lesion is present in an area where the associated tooth has been removed. **Reasoning:** Normally, a radicular cyst requires a non-vital tooth to be present. In this case, the tooth was extracted, but the cystic epithelium was left behind, allowing the cyst to continue growing as a residual radicular cyst. **Takeaway:** A residual radicular cyst occurs when cystic epithelium is left behind after the extraction of a non-vital tooth, allowing the cyst to persist and grow. ## Case: Radicular cyst centered at the tooth apex ### Question **Scenario:** Radiographs of radicular cysts are presented to demonstrate their typical location. **What's shown:** Radiolucent lesions centered directly over the apical foramen of non-vital teeth. **Consider:** Identify the epicenter of the radiolucency in relation to the tooth and explain its clinical significance.  ### Answer **Observations:** - The center of the cystic lesion is located around the apex of the involved tooth. **Reasoning:** Radicular cysts arise from chronic inflammation at the apex of a non-vital tooth. Consequently, the epicenter of the radiolucency is generally centered over the apical foramen, unless it arises from a lateral canal. **Takeaway:** A radicular cyst is typically centered around the apex of a non-vital tooth, reflecting its inflammatory origin at the apical foramen. ## Case: Radicular cyst extending into the maxillary sinus ### Question **Scenario:** A radiograph is presented showing a radicular cyst in the posterior maxilla. **What's shown:** A radiolucent lesion extending into the maxillary sinus, with the buccal plate expanded into a curved, circular shape and appearing very thin. **Consider:** Describe the effect of the lesion on the adjacent anatomical structures and the cortical bone.    ### Answer **Observations:** - The cyst extends into the maxillary sinus, elevating the sinus floor. - The buccal cortical plate is expanded, thinned, and curved. **Reasoning:** As a space-occupying lesion, the radicular cyst expands into the path of least resistance. It can extend into the maxillary sinus while keeping the sinus floor intact, and it causes significant thinning and expansion of the buccal cortical plate. **Takeaway:** Radicular cysts can extend into the maxillary sinus and cause significant expansion and thinning of the buccal cortical plate. Case: Cyst causing inferior displacement of the inferior alveolar canal Radiograph: A dental X-ray showing the lower jaw with teeth, highlighting a large radiolucent area (cyst) indicated by black arrows. The image illustrates the displacement of tooth roots and the inferior alveolar canal caused by the lesion. A dental radiograph showing the maxillary anterior region with a distinct, well-defined radiolucent area located at the root apices of two central incisors. This periapical lesion appears as a dark shadow surrounding the tips of the tooth roots. A dental radiograph (X-ray) showing a cross-section of the jawbone with teeth visible at the top. A distinct, circular radiolucent area (dark spot) is present in the lower right region, illustrating the appearance of a cyst. A dental radiograph (X-ray) showing a cross-section of the jawbone with teeth visible at the top. A distinct, circular radiolucent area (dark spot) is present in the lower right region, illustrating the appearance of a cyst. A A radiograph of the anterior maxilla showing a well-defined, unilocular radiolucency associated with the apex of an incisor tooth. Two black arrows point to the superior border of the lesion, indicating its cortical periphery. B Radiograph: A periapical radiograph showing a large, well-defined radiolucent lesion (cyst) associated with the root of a tooth that has a dense radiopaque restoration. The image illustrates the displacement and resorption of adjacent tooth roots by the expanding cystic structure. B Radiograph showing a periapical lesion associated with a tooth containing a radiopaque restoration. Two white arrows point to the distinct, curved corticated border of the radiolucent area, illustrating the expansion of the cyst. ## Case: Dentigerous cyst causing curved root resorption of tooth 37 ### Question **Scenario:** A radiograph is presented showing a dentigerous cyst affecting an adjacent tooth. **What's shown:** A radiolucent lesion surrounding the crown of an unerupted tooth, with the root of the adjacent tooth 37 showing resorption. **Consider:** Identify the effect of the lesion on the adjacent tooth root and explain the shape of the resorption. ### Answer **Observations:** - Curved resorption of the root of tooth 37. **Reasoning:** The dentigerous cyst acts as a space-occupying lesion. The resorption pattern on the adjacent tooth root has a curved outline because it is being resorbed by the spherical shape of the cyst itself. **Takeaway:** Dentigerous cysts can cause mass effect features, including curved root resorption of adjacent teeth due to the spherical shape of the cyst. ## Case: Radicular cyst histology showing an arcading pattern ### Question **Scenario:** A histological slide of a radicular cyst is presented. **What's shown:** Non-keratinised stratified squamous epithelium with elongated structures extending into the underlying connective tissue. **Consider:** Identify the specific epithelial pattern shown and explain its diagnostic significance. ### Answer **Observations:** - Elongated rete pegs extending into the connective tissue. - A characteristic arcading pattern of the epithelium. **Reasoning:** The proliferative non-keratinised stratified squamous epithelium of a radicular cyst characteristically demonstrates elongated rete pegs in an arcading pattern, which is a key histological feature of this inflammatory cyst. **Takeaway:** Radicular cysts histologically demonstrate non-keratinised stratified squamous epithelium with elongated rete pegs in a characteristic arcading pattern. ## Case: Healing residual cystic cavity with a spoke-wheel pattern ### Question **Scenario:** A radiograph is presented showing a healing bone cavity following cyst treatment. **What's shown:** A central lucent area surrounded by a radiating spoke-wheel pattern of bone trabeculae. **Consider:** Identify the radiographic pattern seen in the healing bone and explain its significance. ### Answer **Observations:** - A radiating spoke-wheel pattern of bone. - A central lucent area. **Reasoning:** When a residual cystic cavity heals, new bone can form in a radiating spoke-wheel pattern, which is a perfectly normal healing response. The central lucent area is also normal and is simply filled with fibrous scar tissue. **Takeaway:** A radiating spoke-wheel pattern with a central lucent area is a normal radiographic sign of a healing residual cystic cavity filled with fibrous scar tissue. ## Case: Dentigerous cyst causing apical displacement of tooth 46 ### Question **Scenario:** A radiograph is presented showing a dentigerous cyst originating from a specific tooth. **What's shown:** A radiolucent lesion surrounding the crown of tooth 46, with the tooth itself positioned deeper in the bone than expected. **Consider:** Identify the positional change of the involved tooth and explain its cause. ### Answer **Observations:** - Tooth 46 is displaced in an apical direction. **Reasoning:** The dentigerous cyst originates from the follicle of tooth 46. As the cyst accumulates fluid and expands, it pushes the involved tooth apically, away from the occlusal plane. **Takeaway:** Dentigerous cysts can cause apical displacement of the involved unerupted tooth as the cyst expands. ## Case: Dentigerous cyst causing curved root resorption of tooth 37 ### Question **Scenario:** A radiograph is presented showing a dentigerous cyst affecting an adjacent tooth. **What's shown:** A radiolucent lesion surrounding the crown of an unerupted tooth, with the root of the adjacent tooth 37 showing resorption. **Consider:** Identify the effect of the lesion on the adjacent tooth root and explain the shape of the resorption.    ### Answer **Observations:** - Curved resorption of the root of tooth 37. **Reasoning:** The dentigerous cyst acts as a space-occupying lesion. The resorption pattern on the adjacent tooth root has a curved outline because it is being resorbed by the spherical shape of the cyst itself. **Takeaway:** Dentigerous cysts can cause mass effect features, including curved root resorption of adjacent teeth due to the spherical shape of the cyst. ## Case: Radicular cyst histology showing an arcading pattern ### Question **Scenario:** A histological slide of a radicular cyst is presented. **What's shown:** Non-keratinised stratified squamous epithelium with elongated structures extending into the underlying connective tissue. **Consider:** Identify the specific epithelial pattern shown and explain its diagnostic significance.  ### Answer **Observations:** - Elongated rete pegs extending into the connective tissue. - A characteristic arcading pattern of the epithelium. **Reasoning:** The proliferative non-keratinised stratified squamous epithelium of a radicular cyst characteristically demonstrates elongated rete pegs in an arcading pattern, which is a key histological feature of this inflammatory cyst. **Takeaway:** Radicular cysts histologically demonstrate non-keratinised stratified squamous epithelium with elongated rete pegs in a characteristic arcading pattern. ## Case: Healing residual cystic cavity with a spoke-wheel pattern ### Question **Scenario:** A radiograph is presented showing a healing bone cavity following cyst treatment. **What's shown:** A central lucent area surrounded by a radiating spoke-wheel pattern of bone trabeculae. **Consider:** Identify the radiographic pattern seen in the healing bone and explain its significance.    ### Answer **Observations:** - A radiating spoke-wheel pattern of bone. - A central lucent area. **Reasoning:** When a residual cystic cavity heals, new bone can form in a radiating spoke-wheel pattern, which is a perfectly normal healing response. The central lucent area is also normal and is simply filled with fibrous scar tissue. **Takeaway:** A radiating spoke-wheel pattern with a central lucent area is a normal radiographic sign of a healing residual cystic cavity filled with fibrous scar tissue. ## Case: Dentigerous cyst causing apical displacement of tooth 46 ### Question **Scenario:** A radiograph is presented showing a dentigerous cyst originating from a specific tooth. **What's shown:** A radiolucent lesion surrounding the crown of tooth 46, with the tooth itself positioned deeper in the bone than expected. **Consider:** Identify the positional change of the involved tooth and explain its cause.  ### Answer **Observations:** - Tooth 46 is displaced in an apical direction. **Reasoning:** The dentigerous cyst originates from the follicle of tooth 46. As the cyst accumulates fluid and expands, it pushes the involved tooth apically, away from the occlusal plane. **Takeaway:** Dentigerous cysts can cause apical displacement of the involved unerupted tooth as the cyst expands. Case: Dentigerous cyst causing curved root resorption of tooth 37 Radiograph: A dental X-ray showing a radiolucent lesion (indicated by the white arrow) adjacent to the root of a tooth, illustrating an internal structure feature. Radiograph: A dental X-ray showing a large, well-defined radiolucent lesion in the posterior mandible. The lesion surrounds the crown of an impacted tooth and has displaced adjacent teeth inferiorly. B Radiograph: A cropped dental radiograph (likely a panoramic or periapical view) showing a large, well-defined radiolucent lesion in the jaw. The lesion surrounds the crown of an impacted tooth located in the upper right quadrant, consistent with the imaging features described for a dentigerous cyst. B Radiograph: A periapical radiograph showing a large, well-defined radiolucent lesion (cyst) associated with the root of a tooth that has a dense radiopaque restoration. The image illustrates the displacement and resorption of adjacent tooth roots by the expanding cystic structure. Histological micrograph showing a cystic lesion with an epithelial lining arranged in a characteristic arcading pattern. Two yellow arrows point to the underlying fibrous connective tissue wall, which is heavily infiltrated by inflammatory cells. Fig. 7.7 Hyaline or Rushton bodies. These translucent or pink-staining lamellar bodies are formed by the cyst lining epithelium and indicate the odontogenic origin of a cyst. A histological micrograph showing several hyaline (Rushton) bodies within the connective tissue. These appear as curved, laminated structures with a characteristic pink-to-purple staining pattern, contrasting against the surrounding pale stroma. Fig. 7.8 Mucous metaplasia in a radicular cyst. The numerous goblet cells can be seen but are more typical of dentigerous cysts. This is a histopathological micrograph showing a section of cyst lining epithelium. The image illustrates mucous metaplasia, characterized by numerous clear, vacuolated goblet cells interspersed within the dark-staining basal layer of the epithelium. Radiograph: A dental X-ray showing a radiolucent lesion (indicated by the white arrow) adjacent to the root of a tooth, illustrating an internal structure feature. ## Case: Dentigerous cyst causing apical displacement of tooth 28 ### Question **Scenario:** A radiograph is presented showing a dentigerous cyst in the maxilla. **What's shown:** A radiolucent lesion associated with an unerupted maxillary tooth, with the tooth positioned high in the maxilla. **Consider:** Identify the positional change of the involved tooth and explain its cause. ### Answer **Observations:** - Tooth 28 is displaced in an apical direction. **Reasoning:** Similar to mandibular teeth, the expansion of the dentigerous cyst in the maxilla exerts pressure on the involved tooth, pushing it apically and superiorly into the maxilla. **Takeaway:** Dentigerous cysts can cause apical displacement of the involved unerupted tooth in the maxilla as the cyst expands. ## Case: Dentigerous cyst causing inferior displacement of the inferior alveolar canal ### Question **Scenario:** A radiograph is presented showing a large dentigerous cyst in the mandible. **What's shown:** A radiolucent lesion in the mandibular body/ramus area, with the inferior alveolar canal positioned lower than its normal anatomical course. **Consider:** Identify the effect of the cyst on the inferior alveolar canal and explain the mechanism. ### Answer **Observations:** - The inferior alveolar canal is displaced inferiorly. **Reasoning:** The large dentigerous cyst occupies space within the mandible, exerting a mass effect that physically pushes the inferior alveolar canal in an inferior direction. **Takeaway:** Large dentigerous cysts in the mandible can cause inferior displacement of the inferior alveolar canal due to their mass effect. ## Case: OKC with a scalloped outline ### Question **Scenario:** A radiograph of an odontogenic keratocyst (OKC) is presented. **What's shown:** A radiolucent lesion in the jaw with a border that forms a series of contiguous arches. **Consider:** Describe the shape of the lesion's border and explain its characteristic appearance. ### Answer **Observations:** - A scalloped outline consisting of a series of contiguous arches. **Reasoning:** While OKCs can be smooth and round, they frequently present with a scalloped outline. This appearance is formed by a series of contiguous arches along the border of the radiolucency. **Takeaway:** OKCs often present with a characteristic scalloped outline, appearing as a series of contiguous arches along the lesion's border. ## Case: OKC with a multilocular appearance and internal septa ### Question **Scenario:** A radiograph of a large odontogenic keratocyst (OKC) is presented. **What's shown:** A large radiolucent lesion containing curved internal opaque lines. **Consider:** Identify the internal features shown and explain their composition and significance. ### Answer **Observations:** - Curved internal septa appearing as opaque lines within the radiolucency. **Reasoning:** When large enough, an OKC can give the appearance of a multilocular lesion with curved internal septa. However, these septa are actually residual, dense bone and are often incomplete, meaning the OKC is not considered a true multilocular lesion with separate compartments. **Takeaway:** Large OKCs can appear multilocular with curved internal septa, but these septa are incomplete residual bone rather than true compartmentalizing walls. ## Case: OKC tunneling along the mandible ### Question **Scenario:** A radiograph of an odontogenic keratocyst (OKC) in the mandible is presented. **What's shown:** A large radiolucent lesion within the mandible that does not appear balloon-like or circular, but rather extends longitudinally through the bone. **Consider:** Describe the growth pattern of this lesion and how it affects the surrounding bone compared to typical cysts. ## Case: Dentigerous cyst causing apical displacement of tooth 28 ### Question **Scenario:** A radiograph is presented showing a dentigerous cyst in the maxilla. **What's shown:** A radiolucent lesion associated with an unerupted maxillary tooth, with the tooth positioned high in the maxilla. **Consider:** Identify the positional change of the involved tooth and explain its cause.  ### Answer **Observations:** - Tooth 28 is displaced in an apical direction. **Reasoning:** Similar to mandibular teeth, the expansion of the dentigerous cyst in the maxilla exerts pressure on the involved tooth, pushing it apically and superiorly into the maxilla. **Takeaway:** Dentigerous cysts can cause apical displacement of the involved unerupted tooth in the maxilla as the cyst expands. ## Case: Dentigerous cyst causing inferior displacement of the inferior alveolar canal ### Question **Scenario:** A radiograph is presented showing a large dentigerous cyst in the mandible. **What's shown:** A radiolucent lesion in the mandibular body/ramus area, with the inferior alveolar canal positioned lower than its normal anatomical course. **Consider:** Identify the effect of the cyst on the inferior alveolar canal and explain the mechanism.    ### Answer **Observations:** - The inferior alveolar canal is displaced inferiorly. **Reasoning:** The large dentigerous cyst occupies space within the mandible, exerting a mass effect that physically pushes the inferior alveolar canal in an inferior direction. **Takeaway:** Large dentigerous cysts in the mandible can cause inferior displacement of the inferior alveolar canal due to their mass effect. ## Case: OKC with a scalloped outline ### Question **Scenario:** A radiograph of an odontogenic keratocyst (OKC) is presented. **What's shown:** A radiolucent lesion in the jaw with a border that forms a series of contiguous arches. **Consider:** Describe the shape of the lesion's border and explain its characteristic appearance.   ### Answer **Observations:** - A scalloped outline consisting of a series of contiguous arches. **Reasoning:** While OKCs can be smooth and round, they frequently present with a scalloped outline. This appearance is formed by a series of contiguous arches along the border of the radiolucency. **Takeaway:** OKCs often present with a characteristic scalloped outline, appearing as a series of contiguous arches along the lesion's border. ## Case: OKC with a multilocular appearance and internal septa ### Question **Scenario:** A radiograph of a large odontogenic keratocyst (OKC) is presented. **What's shown:** A large radiolucent lesion containing curved internal opaque lines. **Consider:** Identify the internal features shown and explain their composition and significance.  ### Answer **Observations:** - Curved internal septa appearing as opaque lines within the radiolucency. **Reasoning:** When large enough, an OKC can give the appearance of a multilocular lesion with curved internal septa. However, these septa are actually residual, dense bone and are often incomplete, meaning the OKC is not considered a true multilocular lesion with separate compartments. **Takeaway:** Large OKCs can appear multilocular with curved internal septa, but these septa are incomplete residual bone rather than true compartmentalizing walls. ## Case: OKC tunneling along the mandible ### Question **Scenario:** A radiograph of an odontogenic keratocyst (OKC) in the mandible is presented. **What's shown:** A large radiolucent lesion within the mandible that does not appear balloon-like or circular, but rather extends longitudinally through the bone. **Consider:** Describe the growth pattern of this lesion and how it affects the surrounding bone compared to typical cysts. Case: Dentigerous cyst causing apical displacement of tooth 28 Radiograph: A dental X-ray showing a large, well-defined radiolucent lesion in the posterior mandible. The lesion surrounds the crown of an impacted tooth and has displaced adjacent teeth inferiorly. A histopathology slide showing a cross-section of tissue with a thin, non-keratinized epithelial lining attached to the CEJ (cementoenamel junction). The cyst wall appears as loose connective tissue, and an arrow indicates a specific area of interest near the attachment site. This is a histopathology micrograph (labeled B) showing a cyst lining consisting of a thin, non-keratinized stratified squamous epithelium resting on a loose, often myxoid, fibrous connective tissue wall. A histopathology micrograph showing a cyst wall with a thin, non-keratinized stratified squamous epithelial lining overlying loose fibrous connective tissue. An orange arrow points to a clear vacuole within the basal layer of the epithelium, likely representing mucous or sebaceous metaplasia. B A dental radiograph (X-ray) showing the posterior mandible. It illustrates a large, well-defined radiolucent lesion with a corticated border that is associated with an impacted tooth. R Radiograph: A panoramic dental X-ray of the posterior mandible showing a large, well-defined radiolucent lesion with a scalloped outline situated between and around the roots of the teeth. The lesion extends superiorly toward the alveolar crest and inferiorly toward the lower border of the mandible. The image displays three radiographic panels labeled A, B, and C. Panel A is a lateral jaw radiograph showing arrows pointing to specific anatomical features or lesions, while Panels B and C are axial CT scans of the mandible (lower jaw) at different levels. ### Answer **Observations:** - The lesion is large but has not ballooned out into a circular shape. - It appears to have grown longitudinally through the bone. **Reasoning:** Unlike other cysts that tend to grow concentrically and expand the bone, the OKC has an insidious growth pattern where it tunnels along the mandible between the cortices with minimal jaw expansion. **Takeaway:** OKCs characteristically tunnel along the bone with minimal expansion for their size, unlike the concentric, ballooning growth seen in other cysts. ## Case: OKC causing inferior displacement of the inferior alveolar canal ### Question **Scenario:** A radiograph of an odontogenic keratocyst (OKC) in the mandible is presented. **What's shown:** A radiolucent lesion in the mandible with a white arrow indicating the position of the inferior alveolar canal, which is located lower than expected. **Consider:** Identify the effect of the OKC on the inferior alveolar canal and explain the mechanism. ### Answer **Observations:** - The inferior alveolar canal is displaced inferiorly. **Reasoning:** As the OKC tunnels and expands within the mandible, it exerts a mass effect on surrounding structures, frequently pushing the inferior alveolar canal in an inferior direction. **Takeaway:** OKCs in the mandible often cause inferior displacement of the inferior alveolar canal due to their mass effect. ## Case: OKC histology showing a flat basal layer and corrugated parakeratin ### Question **Scenario:** Histological slides of an odontogenic keratocyst (OKC) are presented. **What's shown:** Epithelium with a flat basal layer, a corrugated surface, and basal cells with dark nuclei lined up in a specific pattern. **Consider:** Identify the specific epithelial and basal cell features shown and explain their diagnostic significance. ### Answer **Observations:** - A flat basal layer without rete ridges. - A corrugated parakeratin surface. - Palisading basal cells with hypochromatic (dark) nuclei lined up like a picket fence. **Reasoning:** These are the hallmark histological features of an OKC. The thin, regular, folded parakeratinised epithelium lacks rete ridges, has a corrugated surface, and features a characteristic palisading basal layer with hypochromatic nuclei. **Takeaway:** OKCs are characterized histologically by a thin parakeratinised epithelium with a corrugated surface and a palisading basal layer of hypochromatic nuclei. ## Case: Inflammatory collateral cyst causing buccal tipping of teeth 36 and 46 ### Question **Scenario:** A radiograph is presented showing inflammatory collateral cysts affecting mandibular molars. **What's shown:** Teeth 36 and 46 with prominent lingual cusps and root tips pushed lingually, compared to primary molars where cusps are superimposed. **Consider:** Identify the positional changes of the teeth and explain the mechanism behind this presentation. ### Answer **Observations:** - The lingual cusps of teeth 36 and 46 are more prominent and located more superiorly. - The teeth are tilted buccally. **Reasoning:** Because the inflammatory collateral cyst is located on the buccal aspect of the tooth, it exerts pressure that tilts the tooth buccally. This tipping makes the lingual cusps appear more prominent and pushes the root tips into the lingual cortex. **Takeaway:** Inflammatory collateral cysts on the buccal aspect of molars can cause buccal tipping of the tooth, resulting in prominent lingual cusps and root tips pushed into the lingual cortex. ### Answer **Observations:** - The lesion is large but has not ballooned out into a circular shape. - It appears to have grown longitudinally through the bone. **Reasoning:** Unlike other cysts that tend to grow concentrically and expand the bone, the OKC has an insidious growth pattern where it tunnels along the mandible between the cortices with minimal jaw expansion. **Takeaway:** OKCs characteristically tunnel along the bone with minimal expansion for their size, unlike the concentric, ballooning growth seen in other cysts. ## Case: OKC causing inferior displacement of the inferior alveolar canal ### Question **Scenario:** A radiograph of an odontogenic keratocyst (OKC) in the mandible is presented. **What's shown:** A radiolucent lesion in the mandible with a white arrow indicating the position of the inferior alveolar canal, which is located lower than expected. **Consider:** Identify the effect of the OKC on the inferior alveolar canal and explain the mechanism.  ### Answer **Observations:** - The inferior alveolar canal is displaced inferiorly. **Reasoning:** As the OKC tunnels and expands within the mandible, it exerts a mass effect on surrounding structures, frequently pushing the inferior alveolar canal in an inferior direction. **Takeaway:** OKCs in the mandible often cause inferior displacement of the inferior alveolar canal due to their mass effect. ## Case: OKC histology showing a flat basal layer and corrugated parakeratin ### Question **Scenario:** Histological slides of an odontogenic keratocyst (OKC) are presented. **What's shown:** Epithelium with a flat basal layer, a corrugated surface, and basal cells with dark nuclei lined up in a specific pattern. **Consider:** Identify the specific epithelial and basal cell features shown and explain their diagnostic significance.    ### Answer **Observations:** - A flat basal layer without rete ridges. - A corrugated parakeratin surface. - Palisading basal cells with hypochromatic (dark) nuclei lined up like a picket fence. **Reasoning:** These are the hallmark histological features of an OKC. The thin, regular, folded parakeratinised epithelium lacks rete ridges, has a corrugated surface, and features a characteristic palisading basal layer with hypochromatic nuclei. **Takeaway:** OKCs are characterized histologically by a thin parakeratinised epithelium with a corrugated surface and a palisading basal layer of hypochromatic nuclei. ## Case: Inflammatory collateral cyst causing buccal tipping of teeth 36 and 46 ### Question **Scenario:** A radiograph is presented showing inflammatory collateral cysts affecting mandibular molars. **What's shown:** Teeth 36 and 46 with prominent lingual cusps and root tips pushed lingually, compared to primary molars where cusps are superimposed. **Consider:** Identify the positional changes of the teeth and explain the mechanism behind this presentation. ### Answer **Observations:** - The lingual cusps of teeth 36 and 46 are more prominent and located more superiorly. - The teeth are tilted buccally. **Reasoning:** Because the inflammatory collateral cyst is located on the buccal aspect of the tooth, it exerts pressure that tilts the tooth buccally. This tipping makes the lingual cusps appear more prominent and pushes the root tips into the lingual cortex. **Takeaway:** Inflammatory collateral cysts on the buccal aspect of molars can cause buccal tipping of the tooth, resulting in prominent lingual cusps and root tips pushed into the lingual cortex. Case: OKC tunneling along the mandible > Answer The image displays three radiographic panels labeled A, B, and C. Panel A is a lateral jaw radiograph showing arrows pointing to specific anatomical features or lesions, while Panels B and C are axial CT scans of the mandible (lower jaw) at different levels. WHO classification of head and neck tumours, 2017 Histopathology: A photomicrograph of a cystic lesion showing a thin, regular, folded epithelial lining with a corrugated parakeratinized surface and a characteristic palisading basal layer of hyperchromatic nuclei. The underlying connective tissue wall appears uninflamed. Reversal of nuclear polarity of basal layer A photomicrograph of an odontogenic keratocyst lining, showing a thin, regular epithelium with a palisaded basal layer. The dark nuclei of the basal cells are shifted away from the basement membrane towards the upper layers, illustrating the characteristic reversal of nuclear polarity. Satellite cysts and islands in the connective tissue wall A histological micrograph stained with hematoxylin and eosin showing a cyst wall composed of pink connective tissue. Within the fibrous stroma, there are multiple distinct islands and small cystic spaces lined by epithelium, illustrating the presence of satellite cysts. ## Case: Inflammatory collateral cyst superimposed over roots of teeth 36 and 46 ### Question **Scenario:** A radiograph is presented showing an inflammatory collateral cyst in the mandible. **What's shown:** A circular radiolucent region superimposed over the roots of teeth 36 and 46, with a subtle or poorly defined corticated border. **Consider:** Identify the location of the radiolucency and explain why its border might be difficult to detect. ### Answer **Observations:** - A circular radiolucent region superimposed over the roots of the molars. - A subtle or poorly defined corticated border. **Reasoning:** Inflammatory collateral cysts, such as the buccal bifurcation cyst, arise on the buccal aspect of the roots. Because of this buccal location and superimposition over the roots on a 2D radiograph, the corticated border can be subtle and harder to detect. **Takeaway:** Inflammatory collateral cysts may present as a subtle radiolucency superimposed over the roots of recently erupted molars, with a poorly defined border due to their buccal location. ## Case: Inflammatory collateral cyst on CBCT showing root tips in the lingual cortex ### Question **Scenario:** A coronal CBCT slice is presented showing an inflammatory collateral cyst. **What's shown:** A coronal view of the mandible showing buccally tilted molars with their root tips directed toward and contacting the lingual cortical plate. **Consider:** Identify the positional changes of the root tips and explain their relationship to the cyst. ### Answer **Observations:** - The long axis of the teeth is directed such that the apices contact the lingual cortical plate. - The lingual cusp tips are located higher than the buccal cusp tips. **Reasoning:** The buccal location of the cyst pushes the crowns buccally, which in turn forces the root tips lingually. On a coronal CBCT slice, this tipping is clearly visualized as the apices contacting the lingual cortex. **Takeaway:** CBCT imaging clearly demonstrates the buccal tipping of molars caused by inflammatory collateral cysts, showing the root tips pushed into the lingual cortex. ## Case: Inflammatory collateral cyst on occlusal view showing buccal expansion and onion-skin appearance ### Question **Scenario:** Occlusal radiographs are presented showing an inflammatory collateral cyst. **What's shown:** Significant buccal cortical expansion with layers of opaque lines forming a specific pattern. **Consider:** Identify the cortical changes and the specific pattern of the opaque lines, and explain their etiology. ### Answer **Observations:** - Significant buccal cortical expansion. - Layers of opaque lines forming an onion-peel appearance. **Reasoning:** The cyst causes expansion of the buccal cortex. The layers of opaque lines represent periosteal new bone formation laid down sequentially as a result of the chronic infection and inflammation associated with the cyst. **Takeaway:** Inflammatory collateral cysts can cause significant buccal cortical expansion and an onion-peel appearance due to sequential periosteal new bone formation from chronic infection. ## Case: Inflammatory collateral cyst histology showing an open pocket ### Question **Scenario:** A histological slide of an inflammatory collateral cyst is presented. **What's shown:** Inflamed fibrous tissue with hyperplastic epithelium and a distinct open communication to the surface. **Consider:** Identify the specific structural feature shown and explain its clinical correlation. ## Case: Inflammatory collateral cyst superimposed over roots of teeth 36 and 46 ### Question **Scenario:** A radiograph is presented showing an inflammatory collateral cyst in the mandible. **What's shown:** A circular radiolucent region superimposed over the roots of teeth 36 and 46, with a subtle or poorly defined corticated border. **Consider:** Identify the location of the radiolucency and explain why its border might be difficult to detect.  ### Answer **Observations:** - A circular radiolucent region superimposed over the roots of the molars. - A subtle or poorly defined corticated border. **Reasoning:** Inflammatory collateral cysts, such as the buccal bifurcation cyst, arise on the buccal aspect of the roots. Because of this buccal location and superimposition over the roots on a 2D radiograph, the corticated border can be subtle and harder to detect. **Takeaway:** Inflammatory collateral cysts may present as a subtle radiolucency superimposed over the roots of recently erupted molars, with a poorly defined border due to their buccal location. ## Case: Inflammatory collateral cyst on CBCT showing root tips in the lingual cortex ### Question **Scenario:** A coronal CBCT slice is presented showing an inflammatory collateral cyst. **What's shown:** A coronal view of the mandible showing buccally tilted molars with their root tips directed toward and contacting the lingual cortical plate. **Consider:** Identify the positional changes of the root tips and explain their relationship to the cyst.  ### Answer **Observations:** - The long axis of the teeth is directed such that the apices contact the lingual cortical plate. - The lingual cusp tips are located higher than the buccal cusp tips. **Reasoning:** The buccal location of the cyst pushes the crowns buccally, which in turn forces the root tips lingually. On a coronal CBCT slice, this tipping is clearly visualized as the apices contacting the lingual cortex. **Takeaway:** CBCT imaging clearly demonstrates the buccal tipping of molars caused by inflammatory collateral cysts, showing the root tips pushed into the lingual cortex. ## Case: Inflammatory collateral cyst on occlusal view showing buccal expansion and onion-skin appearance ### Question **Scenario:** Occlusal radiographs are presented showing an inflammatory collateral cyst. **What's shown:** Significant buccal cortical expansion with layers of opaque lines forming a specific pattern. **Consider:** Identify the cortical changes and the specific pattern of the opaque lines, and explain their etiology.  ### Answer **Observations:** - Significant buccal cortical expansion. - Layers of opaque lines forming an onion-peel appearance. **Reasoning:** The cyst causes expansion of the buccal cortex. The layers of opaque lines represent periosteal new bone formation laid down sequentially as a result of the chronic infection and inflammation associated with the cyst. **Takeaway:** Inflammatory collateral cysts can cause significant buccal cortical expansion and an onion-peel appearance due to sequential periosteal new bone formation from chronic infection. ## Case: Inflammatory collateral cyst histology showing an open pocket ### Question **Scenario:** A histological slide of an inflammatory collateral cyst is presented. **What's shown:** Inflamed fibrous tissue with hyperplastic epithelium and a distinct open communication to the surface. **Consider:** Identify the specific structural feature shown and explain its clinical correlation.  Case: Inflammatory collateral cyst superimposed over roots of teeth 36 and 46 Two dental radiographs (likely periapical views) showing impacted mandibular third molars. The images illustrate the characteristic pericoronal radiolucencies associated with odontogenic keratocysts, appearing as well-defined dark areas surrounding the crowns of the unerupted teeth. Well-defined corticated lucent lesion Inflammatory periosteal response This border is sclerotic, related to the secondary infection Inflammatory effacement of the buccal cortex. This corresponds with the draining fistula Centred at the bifurcations. Note the tendency to extend distally Slight flattening of the mandibular canal Composite radiographic images including a panoramic view (a) and cross-sectional CT scans (b, c, d) showing the imaging features of a lesion. Red leader lines connect specific anatomical findings to text labels describing them. Well-defined corticated lucent lesion Inflammatory periosteal response This border is sclerotic, related to the secondary infection Inflammatory effacement of the buccal cortex. This corresponds with the draining fistula Centred at the bifurcations. Note the tendency to extend distally Slight flattening of the mandibular canal Composite radiographic images including a panoramic view (a) and cross-sectional CT scans (b, c, d) showing the imaging features of a lesion. Red leader lines connect specific anatomical findings to text labels describing them. A composite histopathology image showing a low-power view of an inflamed cyst wall (left) and a high-power view of the lining epithelium (right). The images illustrate the hyperplastic non-keratinised epithelium described in the diagnostic criteria. ### Answer **Observations:** - An open pocket communicating with the epithelial lining. **Reasoning:** The histology of an inflammatory collateral cyst often demonstrates an open pocket, which correlates clinically with the deep periodontal pocket that can be probed on the buccal aspect of the involved tooth. **Takeaway:** Inflammatory collateral cysts histologically demonstrate an open pocket, correlating with the deep periodontal pocket found clinically on the buccal aspect. ## Case: Lateral periodontal cyst with a heavily corticated border ### Question **Scenario:** A radiograph of a lateral periodontal cyst is presented. **What's shown:** A small, round or oval radiolucent lesion between the roots of vital teeth with a very thick, radiopaque border. **Consider:** Describe the border of the lesion and explain how it differs from typical cysts. ### Answer **Observations:** - A very heavily corticated border that is thicker than the usual corticated margin. **Reasoning:** While lateral periodontal cysts are well-defined, they characteristically have a very heavily corticated border. It is not quite sclerotic, but it is distinctly thicker than the thin, uniform corticated margin seen in most other cysts. **Takeaway:** Lateral periodontal cysts characteristically present with a very heavily corticated border that is thicker than the typical corticated margin of other jaw cysts. ## Case: Botryoid odontogenic cyst with internal septa ### Question **Scenario:** A radiograph of a botryoid odontogenic cyst is presented. **What's shown:** A multilocular radiolucent lesion between the roots of teeth with internal opaque lines separating the spaces. **Consider:** Identify the internal structure of the lesion and explain its relationship to the lateral periodontal cyst. ### Answer **Observations:** - Internal septa creating multiple separate locules. **Reasoning:** The botryoid odontogenic cyst is the multilocular subtype of the lateral periodontal cyst. Unlike the unilocular lateral periodontal cyst, the botryoid variant demonstrates internal septa, giving it a multilocular appearance with multiple separate cystic spaces. **Takeaway:** The botryoid odontogenic cyst is the multilocular subtype of the lateral periodontal cyst, characterized radiographically by internal septa and multiple locules. ## Case: Lateral periodontal cyst histology showing whorled plaque-like epithelial thickenings ### Question **Scenario:** A histological slide of a lateral periodontal cyst is presented. **What's shown:** Thin, non-keratinised epithelium with focal, nodular thickenings. **Consider:** Identify the specific epithelial features shown and explain their diagnostic significance. ### Answer **Observations:** - Focal whorled plaque-like epithelial thickenings. **Reasoning:** The epithelium of a lateral periodontal cyst is typically thin (one to three cells thick) but characteristically demonstrates focal whorled plaque-like epithelial thickenings, which is a key diagnostic histological feature. **Takeaway:** Lateral periodontal cysts histologically demonstrate thin, non-keratinised epithelium with characteristic focal whorled plaque-like epithelial thickenings. ## Case: Surgical ciliated cyst in the anterior maxilla with surgical plates ### Question **Scenario:** A radiograph of the anterior maxilla is presented from a patient with a history of surgery. **What's shown:** A well-defined corticated radiolucency in the anterior maxilla, with surgical plates visible in the surrounding bone. **Consider:** Identify the radiographic findings and correlate them with the patient's surgical history to determine the likely diagnosis. ### Answer **Observations:** - A well-defined, corticated radiolucency in the anterior maxilla. - Presence of surgical plates indicating previous orthognathic surgery. **Reasoning:** The well-defined lucency represents a cyst, and the presence of surgical plates indicates previous trauma or surgery in the region. This combination is characteristic of a surgical ciliated cyst, which develops from entrapped respiratory epithelium following surgery. **Takeaway:** A surgical ciliated cyst should be suspected when a well-defined radiolucency is found in a region with a history of previous surgery or trauma, such as orthognathic surgery. ### Answer **Observations:** - An open pocket communicating with the epithelial lining. **Reasoning:** The histology of an inflammatory collateral cyst often demonstrates an open pocket, which correlates clinically with the deep periodontal pocket that can be probed on the buccal aspect of the involved tooth. **Takeaway:** Inflammatory collateral cysts histologically demonstrate an open pocket, correlating with the deep periodontal pocket found clinically on the buccal aspect. ## Case: Lateral periodontal cyst with a heavily corticated border ### Question **Scenario:** A radiograph of a lateral periodontal cyst is presented. **What's shown:** A small, round or oval radiolucent lesion between the roots of vital teeth with a very thick, radiopaque border. **Consider:** Describe the border of the lesion and explain how it differs from typical cysts.    ### Answer **Observations:** - A very heavily corticated border that is thicker than the usual corticated margin. **Reasoning:** While lateral periodontal cysts are well-defined, they characteristically have a very heavily corticated border. It is not quite sclerotic, but it is distinctly thicker than the thin, uniform corticated margin seen in most other cysts. **Takeaway:** Lateral periodontal cysts characteristically present with a very heavily corticated border that is thicker than the typical corticated margin of other jaw cysts. ## Case: Botryoid odontogenic cyst with internal septa ### Question **Scenario:** A radiograph of a botryoid odontogenic cyst is presented. **What's shown:** A multilocular radiolucent lesion between the roots of teeth with internal opaque lines separating the spaces. **Consider:** Identify the internal structure of the lesion and explain its relationship to the lateral periodontal cyst.   ### Answer **Observations:** - Internal septa creating multiple separate locules. **Reasoning:** The botryoid odontogenic cyst is the multilocular subtype of the lateral periodontal cyst. Unlike the unilocular lateral periodontal cyst, the botryoid variant demonstrates internal septa, giving it a multilocular appearance with multiple separate cystic spaces. **Takeaway:** The botryoid odontogenic cyst is the multilocular subtype of the lateral periodontal cyst, characterized radiographically by internal septa and multiple locules. ## Case: Lateral periodontal cyst histology showing whorled plaque-like epithelial thickenings ### Question **Scenario:** A histological slide of a lateral periodontal cyst is presented. **What's shown:** Thin, non-keratinised epithelium with focal, nodular thickenings. **Consider:** Identify the specific epithelial features shown and explain their diagnostic significance.   ### Answer **Observations:** - Focal whorled plaque-like epithelial thickenings. **Reasoning:** The epithelium of a lateral periodontal cyst is typically thin (one to three cells thick) but characteristically demonstrates focal whorled plaque-like epithelial thickenings, which is a key diagnostic histological feature. **Takeaway:** Lateral periodontal cysts histologically demonstrate thin, non-keratinised epithelium with characteristic focal whorled plaque-like epithelial thickenings. ## Case: Surgical ciliated cyst in the anterior maxilla with surgical plates ### Question **Scenario:** A radiograph of the anterior maxilla is presented from a patient with a history of surgery. **What's shown:** A well-defined corticated radiolucency in the anterior maxilla, with surgical plates visible in the surrounding bone. **Consider:** Identify the radiographic findings and correlate them with the patient's surgical history to determine the likely diagnosis.  ### Answer **Observations:** - A well-defined, corticated radiolucency in the anterior maxilla. - Presence of surgical plates indicating previous orthognathic surgery. **Reasoning:** The well-defined lucency represents a cyst, and the presence of surgical plates indicates previous trauma or surgery in the region. This combination is characteristic of a surgical ciliated cyst, which develops from entrapped respiratory epithelium following surgery. **Takeaway:** A surgical ciliated cyst should be suspected when a well-defined radiolucency is found in a region with a history of previous surgery or trauma, such as orthognathic surgery. Case: Inflammatory collateral cyst histology showing an open pocket > Answer A A dental radiograph showing the roots of posterior teeth with restorations. A well-defined, round radiolucency with a prominent white cortical border is visible adjacent to the root surface in the lower jaw. B Radiograph: A panoramic dental X-ray showing the maxilla and mandible with multiple teeth, including several restorations. In the lower right quadrant (patient's left), a radiolucent lesion is visible in the bone beneath the premolar/molar region. Radiographic cross-section (axial CT slice) of the mandible showing a well-defined, multilocular radiolucent lesion in the anterior region. The image illustrates the cortical boundary and internal septa characteristic of buccal bifurcation cysts or lateral periodontal cysts as described in the accompanying text. Radiograph: A dental X-ray showing a well-defined radiolucent lesion in the jawbone, illustrating the internal structure of a cyst as described in the slide text. Radiograph: A cropped dental X-ray showing a radiolucent lesion with a scalloped, multilocular appearance located between tooth roots in the anterior jaw. A Histopathology micrograph showing cystic spaces lined by a thin, non-keratinised epithelium (indicated by the upper yellow arrow) and a distinct focal, whorled, plaque-like epithelial thickening (indicated by the lower yellow arrow). The wall appears uninflamed. A photomicrograph of a histological section showing multiple cystic spaces separated by fibrous connective tissue septa. The lining epithelium is thin and non-keratinised, appearing as a delicate purple layer surrounding the clear luminal areas. A composite image of six periapical radiographs showing the anterior maxillary region, specifically focusing on the midline between the central incisors. The radiographs display a well-defined radiolucency in this area, consistent with the appearance of a Nasopalatine Duct Cyst (NPDC). Several images illustrate the characteristic heart-shaped border of the lesion caused by superimposition of the nasal spine. ## Case: Orthokeratinised odontogenic cyst histology showing surface keratinization ### Question **Scenario:** A histological slide of an orthokeratinised odontogenic cyst is presented. **What's shown:** A stratified squamous epithelium with a heavily keratinized surface layer lacking cell nuclei. **Consider:** Identify the specific keratinization pattern shown and explain its significance. ### Answer **Observations:** - Heavy surface keratinization. - Absence of cell nuclei in the keratinized layer. **Reasoning:** The term "orthokeratinised" means that the cell nuclei are not present in the keratinized layer. This is in contrast to parakeratinisation, where flattened, condensed nuclei are retained. This feature distinguishes it from the odontogenic keratocyst. **Takeaway:** Orthokeratinised odontogenic cysts histologically demonstrate a thin regular epithelial lining with orthokeratinisation, meaning the keratinized layer lacks cell nuclei. ## Case: Calcifying odontogenic cyst histology showing ghost cells ### Question **Scenario:** A histological slide of a calcifying odontogenic cyst is presented. **What's shown:** Epithelial cells that retain their cell outline but lack visible nuclei. **Consider:** Identify the specific cells shown and explain their diagnostic significance. ### Answer **Observations:** - Cells with visible outlines but absent nuclei. **Reasoning:** These are characteristic "ghost cells." While their presence is characteristic of the calcifying odontogenic cyst and they often calcify, it is important to note that ghost cells can also occur in other odontogenic tumours, so their presence alone does not justify the diagnosis without cystic architecture. **Takeaway:** Calcifying odontogenic cysts are characterized histologically by the presence of ghost cells, which retain their cell outline but lack nuclei. ## Case: Glandular odontogenic cyst showing unilocular and multilocular examples ### Question **Scenario:** Two radiographs of glandular odontogenic cysts are presented. **What's shown:** One radiograph showing a single radiolucent space, and another showing multiple radiolucent spaces separated by opaque lines. **Consider:** Identify the structural variations shown and explain their significance in diagnosing this cyst. ### Answer **Observations:** - One lesion is unilocular. - The other lesion is multilocular with internal septa. **Reasoning:** The glandular odontogenic cyst can present as either a unilocular or multilocular radiolucency. Both presentations demonstrate well-defined corticated borders with smooth, scalloped outlines, and both will exhibit mass effect features like cortical expansion. **Takeaway:** Glandular odontogenic cysts can present as either unilocular or multilocular radiolucent lesions with well-defined, scalloped borders. ## Case: Orthokeratinised odontogenic cyst histology showing surface keratinization ### Question **Scenario:** A histological slide of an orthokeratinised odontogenic cyst is presented. **What's shown:** A stratified squamous epithelium with a heavily keratinized surface layer lacking cell nuclei. **Consider:** Identify the specific keratinization pattern shown and explain its significance.  ### Answer **Observations:** - Heavy surface keratinization. - Absence of cell nuclei in the keratinized layer. **Reasoning:** The term "orthokeratinised" means that the cell nuclei are not present in the keratinized layer. This is in contrast to parakeratinisation, where flattened, condensed nuclei are retained. This feature distinguishes it from the odontogenic keratocyst. **Takeaway:** Orthokeratinised odontogenic cysts histologically demonstrate a thin regular epithelial lining with orthokeratinisation, meaning the keratinized layer lacks cell nuclei. ## Case: Calcifying odontogenic cyst histology showing ghost cells ### Question **Scenario:** A histological slide of a calcifying odontogenic cyst is presented. **What's shown:** Epithelial cells that retain their cell outline but lack visible nuclei. **Consider:** Identify the specific cells shown and explain their diagnostic significance.   ### Answer **Observations:** - Cells with visible outlines but absent nuclei. **Reasoning:** These are characteristic "ghost cells." While their presence is characteristic of the calcifying odontogenic cyst and they often calcify, it is important to note that ghost cells can also occur in other odontogenic tumours, so their presence alone does not justify the diagnosis without cystic architecture. **Takeaway:** Calcifying odontogenic cysts are characterized histologically by the presence of ghost cells, which retain their cell outline but lack nuclei. ## Case: Glandular odontogenic cyst showing unilocular and multilocular examples ### Question **Scenario:** Two radiographs of glandular odontogenic cysts are presented. **What's shown:** One radiograph showing a single radiolucent space, and another showing multiple radiolucent spaces separated by opaque lines. **Consider:** Identify the structural variations shown and explain their significance in diagnosing this cyst.  ### Answer **Observations:** - One lesion is unilocular. - The other lesion is multilocular with internal septa. **Reasoning:** The glandular odontogenic cyst can present as either a unilocular or multilocular radiolucency. Both presentations demonstrate well-defined corticated borders with smooth, scalloped outlines, and both will exhibit mass effect features like cortical expansion. **Takeaway:** Glandular odontogenic cysts can present as either unilocular or multilocular radiolucent lesions with well-defined, scalloped borders. Case: Orthokeratinised odontogenic cyst histology showing surface keratinization A dental radiograph showing the posterior mandible with a large, well-defined radiolucent lesion surrounding the crown of an impacted tooth. Cytologic detail of ghost cells devoid of nuclei but with maintenance of cell outlines. (WHO, 2022) Histopathology slide showing clusters of ghost cells, which appear as pale pink, rounded structures with distinct outlines but lacking nuclei (karyolysis). These are embedded within a background of darker purple connective tissue and epithelial cells. Cystic architecture with prominent basal cells and numerous homogeneous eosinophilic ghost cells. (WHO, 2022) Histopathology slide showing a cystic lesion lined by stratified epithelium with prominent basal cells and numerous homogeneous eosinophilic ghost cells. An orange arrow points to the region of ghost cell accumulation within the epithelial lining. Radiograph: Two dental imaging panels (A and B) illustrating the features of a glandular odontogenic cyst. Panel A is an anterior mandibular occlusal radiograph showing a multilocular radiolucency with scalloped borders in the symphysis region. Panel B is an axial CT scan demonstrating expansion of the cortical plates and perforation by the lesion. [^1]: Original PDF page 1: [[L3.1 - Cysts of the Jaws.pdf#page=1|L3.1 - Cysts of the Jaws, p.1]] [^2]: Original PDF page 2: [[L3.1 - Cysts of the Jaws.pdf#page=2|L3.1 - Cysts of the Jaws, p.2]] [^3]: Original PDF page 3: [[L3.1 - Cysts of the Jaws.pdf#page=3|L3.1 - Cysts of the Jaws, p.3]] [^4]: Original PDF page 4: [[L3.1 - Cysts of the Jaws.pdf#page=4|L3.1 - Cysts of the Jaws, p.4]] [^5]: Original PDF page 5: [[L3.1 - Cysts of the Jaws.pdf#page=5|L3.1 - Cysts of the Jaws, p.5]] [^6]: Original PDF page 6: [[L3.1 - Cysts of the Jaws.pdf#page=6|L3.1 - Cysts of the Jaws, p.6]] [^7]: Original PDF page 7: [[L3.1 - Cysts of the Jaws.pdf#page=7|L3.1 - Cysts of the Jaws, p.7]] [^8]: Original PDF page 8: [[L3.1 - Cysts of the Jaws.pdf#page=8|L3.1 - Cysts of the Jaws, p.8]] [^9]: Original PDF page 9: [[L3.1 - Cysts of the Jaws.pdf#page=9|L3.1 - Cysts of the Jaws, p.9]] [^10]: Original PDF page 10: [[L3.1 - Cysts of the Jaws.pdf#page=10|L3.1 - Cysts of the Jaws, p.10]] [^11]: Original PDF page 11: [[L3.1 - Cysts of the Jaws.pdf#page=11|L3.1 - Cysts of the Jaws, p.11]] [^12]: Original PDF page 12: [[L3.1 - Cysts of the Jaws.pdf#page=12|L3.1 - Cysts of the Jaws, p.12]] [^13]: Original PDF page 13: [[L3.1 - Cysts of the Jaws.pdf#page=13|L3.1 - Cysts of the Jaws, p.13]] [^14]: Original PDF page 14: [[L3.1 - Cysts of the Jaws.pdf#page=14|L3.1 - Cysts of the Jaws, p.14]] [^15]: Original PDF page 15: [[L3.1 - Cysts of the Jaws.pdf#page=15|L3.1 - Cysts of the Jaws, p.15]] [^16]: Original PDF page 16: [[L3.1 - Cysts of the Jaws.pdf#page=16|L3.1 - Cysts of the Jaws, p.16]] [^17]: Original PDF page 17: [[L3.1 - Cysts of the Jaws.pdf#page=17|L3.1 - Cysts of the Jaws, p.17]] [^18]: Original PDF page 18: [[L3.1 - Cysts of the Jaws.pdf#page=18|L3.1 - Cysts of the Jaws, p.18]] [^19]: Original PDF page 19: [[L3.1 - Cysts of the Jaws.pdf#page=19|L3.1 - Cysts of the Jaws, p.19]] [^20]: Original PDF page 20: [[L3.1 - Cysts of the Jaws.pdf#page=20|L3.1 - Cysts of the Jaws, p.20]] [^21]: Original PDF page 21: [[L3.1 - Cysts of the Jaws.pdf#page=21|L3.1 - Cysts of the Jaws, p.21]] [^22]: Original PDF page 22: [[L3.1 - Cysts of the Jaws.pdf#page=22|L3.1 - Cysts of the Jaws, p.22]] [^23]: Original PDF page 23: [[L3.1 - Cysts of the Jaws.pdf#page=23|L3.1 - Cysts of the Jaws, p.23]] [^24]: Original PDF page 24: [[L3.1 - Cysts of the Jaws.pdf#page=24|L3.1 - Cysts of the Jaws, p.24]] [^25]: Original PDF page 25: [[L3.1 - Cysts of the Jaws.pdf#page=25|L3.1 - Cysts of the Jaws, p.25]] [^26]: Original PDF page 26: [[L3.1 - Cysts of the Jaws.pdf#page=26|L3.1 - Cysts of the Jaws, p.26]] [^27]: Original PDF page 27: [[L3.1 - Cysts of the Jaws.pdf#page=27|L3.1 - Cysts of the Jaws, p.27]] [^28]: Original PDF page 28: [[L3.1 - Cysts of the Jaws.pdf#page=28|L3.1 - Cysts of the Jaws, p.28]] [^29]: Original PDF page 29: [[L3.1 - Cysts of the Jaws.pdf#page=29|L3.1 - Cysts of the Jaws, p.29]] [^30]: Original PDF page 30: [[L3.1 - Cysts of the Jaws.pdf#page=30|L3.1 - Cysts of the Jaws, p.30]] [^31]: Original PDF page 31: [[L3.1 - Cysts of the Jaws.pdf#page=31|L3.1 - Cysts of the Jaws, p.31]] [^32]: Original PDF page 32: [[L3.1 - Cysts of the Jaws.pdf#page=32|L3.1 - Cysts of the Jaws, p.32]] [^33]: Original PDF page 33: [[L3.1 - Cysts of the Jaws.pdf#page=33|L3.1 - Cysts of the Jaws, p.33]] [^34]: Original PDF page 34: [[L3.1 - Cysts of the Jaws.pdf#page=34|L3.1 - Cysts of the Jaws, p.34]] [^35]: Original PDF page 35: [[L3.1 - Cysts of the Jaws.pdf#page=35|L3.1 - Cysts of the Jaws, p.35]] [^36]: Original PDF page 36: [[L3.1 - Cysts of the Jaws.pdf#page=36|L3.1 - Cysts of the Jaws, p.36]] [^37]: Original PDF page 37: [[L3.1 - Cysts of the Jaws.pdf#page=37|L3.1 - Cysts of the Jaws, p.37]] [^38]: Original PDF page 38: [[L3.1 - Cysts of the Jaws.pdf#page=38|L3.1 - Cysts of the Jaws, p.38]] [^39]: Original PDF page 39: [[L3.1 - Cysts of the Jaws.pdf#page=39|L3.1 - Cysts of the Jaws, p.39]] [^40]: Original PDF page 40: [[L3.1 - Cysts of the Jaws.pdf#page=40|L3.1 - Cysts of the Jaws, p.40]] [^41]: Original PDF page 41: [[L3.1 - Cysts of the Jaws.pdf#page=41|L3.1 - Cysts of the Jaws, p.41]] [^42]: Original PDF page 42: [[L3.1 - Cysts of the Jaws.pdf#page=42|L3.1 - Cysts of the Jaws, p.42]] [^43]: Original PDF page 43: [[L3.1 - Cysts of the Jaws.pdf#page=43|L3.1 - Cysts of the Jaws, p.43]] [^44]: Original PDF page 44: [[L3.1 - Cysts of the Jaws.pdf#page=44|L3.1 - Cysts of the Jaws, p.44]] [^45]: Original PDF page 45: [[L3.1 - Cysts of the Jaws.pdf#page=45|L3.1 - Cysts of the Jaws, p.45]] [^46]: Original PDF page 46: [[L3.1 - Cysts of the Jaws.pdf#page=46|L3.1 - Cysts of the Jaws, p.46]] [^47]: Original PDF page 47: [[L3.1 - Cysts of the Jaws.pdf#page=47|L3.1 - Cysts of the Jaws, p.47]] [^48]: Original PDF page 48: [[L3.1 - Cysts of the Jaws.pdf#page=48|L3.1 - Cysts of the Jaws, p.48]] [^49]: Original PDF page 49: [[L3.1 - Cysts of the Jaws.pdf#page=49|L3.1 - Cysts of the Jaws, p.49]] [^50]: Original PDF page 50: [[L3.1 - Cysts of the Jaws.pdf#page=50|L3.1 - Cysts of the Jaws, p.50]] [^51]: Original PDF page 51: [[L3.1 - Cysts of the Jaws.pdf#page=51|L3.1 - Cysts of the Jaws, p.51]] [^52]: Original PDF page 52: [[L3.1 - Cysts of the Jaws.pdf#page=52|L3.1 - Cysts of the Jaws, p.52]] [^53]: Original PDF page 53: [[L3.1 - Cysts of the Jaws.pdf#page=53|L3.1 - Cysts of the Jaws, p.53]] [^54]: Original PDF page 54: [[L3.1 - Cysts of the Jaws.pdf#page=54|L3.1 - Cysts of the Jaws, p.54]] [^55]: Original PDF page 55: [[L3.1 - Cysts of the Jaws.pdf#page=55|L3.1 - Cysts of the Jaws, p.55]] [^56]: Original PDF page 56: [[L3.1 - Cysts of the Jaws.pdf#page=56|L3.1 - Cysts of the Jaws, p.56]] [^57]: Original PDF page 57: [[L3.1 - Cysts of the Jaws.pdf#page=57|L3.1 - Cysts of the Jaws, p.57]] [^58]: Original PDF page 58: [[L3.1 - Cysts of the Jaws.pdf#page=58|L3.1 - Cysts of the Jaws, p.58]] [^59]: Original PDF page 59: [[L3.1 - Cysts of the Jaws.pdf#page=59|L3.1 - Cysts of the Jaws, p.59]]