BENIGN TUMOURS OF THE JAWS (PART 1 — ODONTOGENIC TUMOURS) Dr. May Lam Oral and Maxillofacial Radiologist Senior lecturer BDSc (Hons) FRACDS (GDP) DClinDent (DMFR) MRACDS (DMFR) Part 1 — Odontogenic Tumours Dr. May Lam Oral and Maxillofacial Radiologist, Senior Lecturer BDSc (Hons) FRACDS (GDP) DClinDent (DMFR) MRACDS (DMFR) WHAT IS A BENIGN TUMOUR? **Definition:** an abnormal mass of tissue that exhibits uncontrolled and uncoordinated growth, persisting even after the stimuli that initiated the growth have ceased. It tends to be slow-growing, well-differentiated and well-circumscribed, resemble the tissue of origin, and remain localised to the site of origin. **Clinical Features:** * Insidious onset with slow growth * Painless * Does not metastasise **Definition:** an abnormal mass of tissue that exhibits uncontrolled and uncoordinated growth, persisting even after the stimuli that initiated the growth have ceased. It tends to be slow-growing, well-differentiated and well-circumscribed, resemble the tissue of origin, and remain localised to the site of origin. #### Clinical Features - Insidious onset with slow growth - Painless - Does not metastasise # GENERAL IMAGING FEATURES **Location:** * Have specific anatomical predilection * E.g. odontogenic tumours occur in the alveolar processes, above the IAC; cartilaginous tumours occur in jaw locations with residual cartilaginous cells **Periphery/Shape:** * Usually smooth, well-defined, sometimes corticated borders * Due to the slow enlargement by formation of additional internal tissue * May be unilocular or multilocular * A radiolucent band may be seen * This represents a soft tissue capsule    #### Location - Have specific anatomical predilection - E.g. odontogenic tumours occur in the alveolar processes, above the IAC; cartilaginous tumours occur in jaw locations with residual cartilaginous cells #### Periphery and Shape - Usually smooth, well-defined, sometimes corticated borders - Due to the slow enlargement by formation of additional internal tissue - May be unilocular or multilocular - A radiolucent band may be seen - This represents a soft tissue capsule - ==The anatomical location can help narrow the differential diagnosis, including the specific jaw, anterior or posterior position, relationship to teeth, and relationship to the inferior alveolar canal or maxillary sinus.== - ==A corticated border appears as a thin radiopaque line and reflects slow tumour enlargement with formation of additional internal tissue.== - ==The radiolucent band may be present around a lesion and may represent a soft-tissue capsule.== Radiograph: A dental X-ray showing the posterior mandible with a large, multilocular radiolucent lesion containing an impacted tooth. The image illustrates specific anatomical features such as the smooth, well-defined borders and internal compartmentalization typical of jaw pathology. Radiograph: A periapical dental X-ray showing the roots of several teeth embedded in the alveolar bone. Radiograph: A dental X-ray showing the posterior teeth of the upper and lower jaws, illustrating a well-defined radiolucent lesion in the mandibular bone behind the last molar. The image demonstrates smooth borders and potential multilocularity or internal structures consistent with an odontogenic tumour. # GENERAL IMAGING FEATURES Internal Structure: * Variable * May be totally RL, totally RO, or a mixture of RL/RO tissues * If the lesion contains RO elements, these usually represent residual bone, reactive bone formation, or a calcified material produced by the tumour * The internal pattern may be characteristic for specific types of tumours * E.g. curved coarse septa are characteristic for ameloblastomas Effects on Surrounding Structures: * Displacement and resorption of teeth * Expansion and thinning of the jaw cortices +/- perforation * Displacement of the inferior alveolar canal (IAC) * Elevation of the antral +/- nasal cortical floors White and Pharoah, 2014   #### Internal Structure - Variable - May be totally RL, totally RO, or a mixture of RL/RO tissues - If the lesion contains RO elements, these usually represent residual bone, reactive bone formation, or a calcified material produced by the tumour - The internal pattern may be characteristic for specific types of tumours - E.g. curved coarse septa are characteristic for ameloblastomas #### Effects on Surrounding Structures - Displacement and resorption of teeth - Expansion and thinning of the jaw cortices +/- perforation - Displacement of the inferior alveolar canal (IAC) - Elevation of the antral +/- nasal cortical floors *White and Pharoah, 2014* > [!note] Lecturer — Ameloblastoma Septa > Coarse, curved septa are particularly characteristic of ameloblastoma. > > - They represent residual bone trapped within the tumour and remodelled into a curved shape by internal cystic structures. > [!note] Lecturer — Tumour Mass Effect > Benign tumours produce space-occupying or mass-effect features because they grow by taking up space. > > - Root resorption is more common with benign tumours than with cysts and may produce blunting of the roots. > - Pressure against the cortex causes resorption of the inner cortical surface, while the periosteum deposits new bone on the outer surface. > - Repeated remodelling results in expansion and thinning of the cortices, with possible cortical perforation if the lesion grows faster than periosteal bone formation. A dental radiograph (likely a periapical or panoramic view) showing the mandible with teeth, including one with a metallic restoration. A white arrow points to an expansile lesion in the jawbone characterized by a multilocular radiolucent appearance with internal septa, illustrating the 'internal structure' and 'expansion of jaw cortices' features discussed in the text. A periapical dental radiograph showing the posterior mandible with multiple teeth exhibiting large, bright white restorations (radiopaque). The image illustrates general imaging features such as the internal structure of bone and potential effects on surrounding structures like tooth displacement or resorption. # WHO CLASSIFICATION OF HEAD AND NECK TUMOURS 5^TH ED (2022) **Odontogenic Benign Tumours** * **Benign epithelial odontogenic tumours** * Ameloblastoma * Ameloblastoma, conventional * Ameloblastoma, unicystic type * Ameloblastoma, extraosseous/peripheral type * Adenoid ameloblastoma * Metastasising ameloblastoma * Adenomatoid odontogenic tumour * Squamous odontogenic tumour * Calcifying epithelial odontogenic tumour * **Benign mixed epithelial & mesenchymal odontogenic tumours** * Odontoma * Ameloblastic fibroma * Primordial odontogenic tumour * Dentinogenic ghost cell tumour * **Benign mesenchymal odontogenic tumours** * Odontogenic myxoma/myxofibroma * Odontogenic fibroma * Cementoblastoma * Cemento-ossifying fibroma **Non-Odontogenic Benign Tumours** * **Benign maxillofacial bone and cartilage tumours** * Osteoma * Osteochondroma * Osteoblastoma * (Osteoid osteoma) * Chondroblastoma * Chondromyxoid fibroma * Desmoplastic fibroma of bone * **Soft tissue tumours** * Vascular tumours * Haemangioma * Peripheral nerve sheath tumours * Neurofibroma * Schwannoma * Neuroma 5th ed (2022) #### Odontogenic Benign Tumours - **Benign epithelial odontogenic tumours** - Ameloblastoma - Ameloblastoma, conventional - Ameloblastoma, unicystic type - Ameloblastoma, extraosseous/peripheral type - Adenoid ameloblastoma - Metastasising ameloblastoma - Adenomatoid odontogenic tumour - Squamous odontogenic tumour - Calcifying epithelial odontogenic tumour - **Benign mixed epithelial & mesenchymal odontogenic tumours** - Odontoma - Ameloblastic fibroma - Primordial odontogenic tumour - Dentinogenic ghost cell tumour - **Benign mesenchymal odontogenic tumours** - Odontogenic myxoma/myxofibroma - Odontogenic fibroma - Cementoblastoma - Cemento-ossifying fibroma #### Non-Odontogenic Benign Tumours - **Benign maxillofacial bone and cartilage tumours** - Osteoma - Osteochondroma - Osteoblastoma - (Osteoid osteoma) - Chondroblastoma - Chondromyxoid fibroma - Desmoplastic fibroma of bone - **Soft tissue tumours** - Vascular tumours - Haemangioma - Peripheral nerve sheath tumours - Neurofibroma - Schwannoma - Neuroma - ==Ameloblastic fibro-odontoma== # PART 1: BENIGN EPITHELIAL ODONTOGENIC TUMOURS 1. Ameloblastoma Ameloblastoma, conventional Ameloblastoma, unicystic type Ameloblastoma, extraosseous/peripheral type Adenoid ameloblastoma Metastasizing ameloblastoma 2. Adenomatoid odontogenic tumour 3. Squamous odontogenic tumour 4. Calcifying epithelial odontogenic tumour 1. Ameloblastoma - Ameloblastoma, conventional - Ameloblastoma, unicystic type - Ameloblastoma, extraosseous/peripheral type - Adenoid ameloblastoma - Metastasizing ameloblastoma 2. Adenomatoid odontogenic tumour 3. Squamous odontogenic tumour 4. Calcifying epithelial odontogenic tumour # 1.1 AMELOBLASTOMA | **Definition** | A benign but locally infiltrative epithelial odontogenic neoplasm of the jawbones characterised by ameloblast-like cells and stellate reticulum. | | :--- | :--- | | **Types** | 1. Conventional (aka Solid-multicystic) (92%)<br>• Follicular, plexiform, acanthomatous, granular cell, basal cell, desmoplastic<br>2. Unicystic (6%)<br>3. Extraosseous/Peripheral<br>4. Adenoid ameloblastoma<br>5. Metastasizing ameloblastoma | | **Prevalence** | The most common odontogenic tumour in all ethnic groups (excluding odontomas)<br>~1% of all H+N neoplasms, with highest incidence in African and Afro-Caribbean populations | | **Age** | Peak incidence = 4th – 5th decades<br>Range = 8-92 years | | **Gender** | M=F |  | **Definition** | A benign but locally infiltrative epithelial odontogenic neoplasm of the jawbones characterised by ameloblast-like cells and stellate reticulum. | |---|---| | **Types** | 1. Conventional (aka Solid-multicystic) (92%) - Follicular, plexiform, acanthomatous, granular cell, basal cell, desmoplastic 2. Unicystic (6%) 3. Extraosseous/Peripheral 4. Adenoid ameloblastoma 5. Metastasizing ameloblastoma | |---|---| | **Prevalence** | The most common odontogenic tumour in all ethnic groups (excluding odontomas) ~1% of all H+N neoplasms, with highest incidence in African and Afro-Caribbean populations | |---|---| | **Age** | Peak incidence = 4th – 5th decades Range = 8-92 years | |---|---| | **Gender** | M=F | |---|---| A structured table presenting key clinical and pathological characteristics of Ameloblastoma. The rows define the condition, list its five types with prevalence percentages, detail its epidemiology (prevalence), age distribution, and gender ratio. 1.1.1 AMELOBLASTOMA | Aetiology | Arises from the dental lamina<br>Mutations in the MAPK pathway present in almost 90% of ameloblastomas<br>• BRAFV600E being the most common mutation | | :--- | :--- | | **Clinical Features** | A painless, slow-growing mass that, if untreated, reaches a large size, displaces and loosens teeth, expands and perforates the cortices, may cause paraesthesia and ultimately causes disfigurement and risks adjacent vital structures |   | **Aetiology** | Arises from the dental lamina Mutations in the MAPK pathway present in almost 90% of ameloblastomas - BRAF V600E being the most common mutation | |---|---| | **Clinical Features** | A painless, slow-growing mass that, if untreated, reaches a large size, displaces and loosens teeth, expands and perforates the cortices, may cause paraesthesia and ultimately causes disfigurement and risks adjacent vital structures | |---|---| - ==Ameloblastoma is one of the tumours most likely to be encountered in dental practice==. - ==It is much less common than ameloblastoma.== A two-row table with blue headers on the left and light blue content cells on the right. The first row is titled 'Aetiology' and lists origins from the dental lamina and MAPK pathway mutations (specifically BRAFV600E). The second row is titled 'Clinical Features' and describes a painless, slow-growing mass that displaces teeth and expands cortices. Clinical photograph showing a large, painless, slow-growing mass on the lower jaw that has caused significant facial disfigurement. 1.1.1 CONVENTIONAL AMELOBLASTOMA | Location | Mandible (87%) <br> Post Md > Ant Md > Post Mx* > Ant Mx <br> * Often extends into the Mx sinus & nasal floor <br> NB: Desmoplastic ameloblastoma has predilection for anterior region of jaws, esp. Mx; Md = Mx <br> NB: Ameloblastomas of the sinonasal tract are rare | | :--- | :--- | | **Periphery/ Shape** | Well-defined, corticated, curved <br> NB: Mx lesions are often more ill-defined | White & Pharoah, 2014    | **Location** | Mandible (87%) Post Md > Ant Md > Post Mx* > Ant Mx * Often extends into the Mx sinus & nasal floor NB: Desmoplastic ameloblastoma has predilection for anterior region of jaws, esp. Mx; Md = Mx NB: Ameloblastomas of the sinonasal tract are rare | |---|---| | **Periphery/ Shape** | Well-defined, corticated, curved NB: Mx lesions are often more ill-defined | |---|---| *White & Pharoah, 2014* A two-row informational table with blue headers for 'Location' and 'Periphery/ Shape'. The content details the anatomical distribution of ameloblastomas, noting a high prevalence in the mandible (87%) and specific posterior-to-anterior ordering, alongside descriptions of lesion characteristics such as being well-defined, corticated, and curved. The image displays two radiographic views of a jaw, likely an orthopantomogram and a lateral or oblique view. Both show extensive multilocular radiolucencies with well-defined borders, creating a characteristic "soap bubble" or "honeycomb" appearance within the bone. A dental radiograph showing the posterior mandible with a large, well-defined multilocular radiolucent lesion containing curved corticated borders and displacing associated teeth. 1.1.1 CONVENTIONAL AMELOBLASTOMA | Internal Features | Multilocular soap-bubble or honeycomb radiolucency (most common) <br> • Coarse, curved septae originating from normal bone trapped between cystic components <br> • Locule size is smaller for anterior lesions and larger for posterior lesions <br> Unilocular appearance is less common <br> Desmoplastic AM may produce fine honeycomb mixed RL appearance resembling a fibro-osseous lesion | | :--- | :--- | | **Surrounding Features** | Buccal/lingual expansion (“eggshell”) +/- perforation <br> Straight edge blunting root resorption <br> Tooth displacement (inc. apically) <br> May be associated with UE/impacted tooth (18%) | White & Pharoah, 2014 WHO, 2022     | **Internal Features** | Multilocular soap-bubble or honeycomb radiolucency (most common) - Coarse, curved septae originating from normal bone trapped between cystic components - Locule size is smaller for anterior lesions and larger for posterior lesions Unilocular appearance is less common Desmoplastic AM may produce fine honeycomb mixed RL appearance resembling a fibro-osseous lesion | |---|---| | **Surrounding Features** | Buccal/lingual expansion ("eggshell") +/- perforation Straight edge blunting root resorption Tooth displacement (inc. apically) May be associated with UE/impacted tooth (18%) | |---|---| *White & Pharoah, 2014* *WHO, 2022* A two-row table detailing the radiographic characteristics of conventional ameloblastoma, categorized into 'Internal Features' and 'Surrounding Features'. The left column contains blue headers with white text, while the right column lists specific diagnostic signs such as multilocular soap-bubble or honeycomb radiolucency, unilocular appearance, buccal/lingual expansion, and root resorption. Radiograph: A panoramic dental X-ray showing the mandible with a large, multilocular radiolucent lesion in the anterior region. The lesion exhibits a coarse, curved septae pattern creating a "soap-bubble" or honeycomb appearance, consistent with the internal features of a conventional ameloblastoma. Radiograph: A dental radiograph showing a lesion with mixed radiolucent and radiopaque features, indicated by black arrows, alongside unilocular radiolucencies marked by white arrows. A composite medical image featuring an axial CT scan (top, labeled 'A') and a panoramic dental radiograph (bottom). The images illustrate the internal features of a lesion in the mandible, specifically showing a multilocular radiolucency with coarse septae ('soap-bubble' appearance) and associated root resorption and tooth displacement. 1.1.1 CONVENTIONAL AMELOBLASTOMA | | | | :--- | :--- | | **Dentigerous cyst** | Small unilocular AM located around crown of UE tooth may be indistinguishable | | **Odontogenic keratocyst** | Tends to grow along bone without marked expansion<br>May also have curved septa (uncommon) | | **Giant cell granuloma** | **Younger** age group (unless brown tumour related to hyperparathyroidism)<br>More granular or wispy, **ill-defined septa** | | **Odontogenic myxoma** | Similar septa, but usually have 1-2 thin, sharp, **straight septa**<br>Tend to grow along bone & **less expansile** than ameloblastoma | | **Ossifying fibroma** | Septa are usually wide, granular, **ill-defined**<br>Often there are small, irregular trabeculae | | **Aneurysmal bone cyst** | **Fine internal septa**<br>Typically **extremely expansive** |  | **Dentigerous cyst** | Small unilocular AM located around crown of UE tooth may be indistinguishable | |---|---| | **Odontogenic keratocyst** | Tends to grow along bone without marked expansion May also have curved septa (uncommon) | |---|---| | **Giant cell granuloma** | **Younger** age group (unless brown tumour related to hyperparathyroidism) More granular or wispy, **ill-defined septa** | |---|---| | **Odontogenic myxoma** | Similar septa, but usually have 1-2 thin, sharp, **straight septa** Tend to grow along bone & **less expansile** than ameloblastoma | |---|---| | **Ossifying fibroma** | Septa are usually wide, granular, **ill-defined** Often there are small, irregular trabeculae | |---|---| | **Aneurysmal bone cyst** | **Fine internal septa** Typically **extremely expansive** | |---|---| A two-column table listing differential diagnoses for conventional ameloblastoma, including dentigerous cyst, odontogenic keratocyst, giant cell granuloma, odontogenic myxoma, ossifying fibroma, and aneurysmal bone cyst. Each row provides distinguishing features such as septa characteristics, expansility, and growth patterns. 1.1.1 CONVENTIONAL AMELOBLASTOMA Follicular type (most common) • Islands of odontogenic epithelium with columnar peripheral cells • Hyperchromatic nuclei with palisading pattern & reverse polarity • Reminiscent of the enamel organ (ameloblast-like peripheral cells with a central core of akin to stellate reticulum which often undergoes cystic degeneration) • Connective tissue is moderate to highly collagenised Plexiform type • Strands & cords of ameloblastomatous epithelium that form anastomoses • Peripheral cells: less pronounced • Inconspicuous stellate reticulum • Connective tissue: loose & often undergoes cystic changes   #### Follicular Type (Most Common) - Islands of odontogenic epithelium with columnar peripheral cells - Hyperchromatic nuclei with palisading pattern & reverse polarity - Reminiscent of the enamel organ (ameloblast-like peripheral cells with a central core akin to stellate reticulum which often undergoes cystic degeneration) - Connective tissue is moderate to highly collagenised #### Plexiform Type - Strands & cords of ameloblastomatous epithelium that form anastomoses - Peripheral cells: less pronounced - Inconspicuous stellate reticulum - Connective tissue: loose & often undergoes cystic changes Histopathology micrograph showing islands of odontogenic epithelium set within a collagenous connective tissue stroma. The epithelial nests exhibit peripheral columnar cells with hyperchromatic nuclei and reverse polarity, surrounding a central core of loosely arranged cells resembling stellate reticulum. A histological micrograph showing the plexiform pattern of a conventional ameloblastoma, characterized by anastomosing strands and cords of epithelial cells within a loose connective tissue stroma. 1.1.1 CONVENTIONAL AMELOBLASTOMA • Squamous metaplasia in stellate reticulum-like central areas • May have keratin pearl formation Other types: Basaloid, desmoplastic, clear cell Mixed patterns are seen frequently Infiltration into bony trabeculae is commonly seen • Granular change in the stellate reticulum-like central areas No clinical significance is associated with these histological patterns   - Squamous metaplasia in stellate reticulum-like central areas - May have keratin pearl formation - Granular change in the stellate reticulum-like central areas Other types: Basaloid, desmoplastic, clear cell Mixed patterns are seen frequently Infiltration into bony trabeculae is commonly seen No clinical significance is associated with these histological patterns A photomicrograph of a histological section stained with hematoxylin and eosin, showing islands of odontogenic epithelium. The tissue demonstrates squamous metaplasia within the central stellate reticulum-like areas, characteristic of the acanthomatous variant. Micrograph of a histological section showing islands of odontogenic epithelium with central areas containing cells exhibiting granular cytoplasm, surrounded by fibrous connective tissue stroma. # 1.1.1 CONVENTIONAL AMELOBLASTOMA ## MANAGEMENT * Complete excision with negative margins, irrespective of histopathological subtype * This may involve a segmental resection, mandibulectomy or maxillectomy, depending on lesion size * Requires removal of bone margin of at least 10mm beyond radiographic margin * Maxillary lesions are usually treated more aggressively * BRAF inhibitor treatment has been proposed, alone or in combination with MAPK/ERK kinase (MEK) inhibitors ## PROGNOSIS/RECURRENCE * Recurrence rate = approx. 60-80% with conservative surgery * Long follow up (1-2 decades) is mandatory – consider lifelong  #### Management - Complete excision with negative margins, irrespective of histopathological subtype - This may involve a segmental resection, mandibulectomy or maxillectomy, depending on lesion size - Requires removal of bone margin of at least 10mm beyond radiographic margin - Maxillary lesions are usually treated more aggressively - BRAF inhibitor treatment has been proposed, alone or in combination with MAPK/ERK kinase (MEK) inhibitors #### Prognosis/Recurrence - Recurrence rate = approx. 60-80% with conservative surgery - Long follow up (1-2 decades) is mandatory – consider lifelong A panoramic radiograph (orthopantomogram) showing the maxilla and mandible with dentition. A large, well-defined radiolucent lesion is visible in the posterior mandible, extending from the molar region towards the ramus. 1.1.1 RECURRENT AMELOBLASTOMA Multiple small cyst-like structures with very coarse sclerotic cortical margins, sometimes separated by normal bone More aggressive both radiographically & histologically than the original lesion White & Pharoah, 2014   Multiple small cyst-like structures with very coarse sclerotic cortical margins, sometimes separated by normal bone More aggressive both radiographically & histologically than the original lesion *White & Pharoah, 2014* Radiograph: This dental X-ray displays the roots of two teeth surrounded by alveolar bone exhibiting a multilocular, "soap-bubble" radiolucency. The lesion is characterized by multiple small cyst-like structures separated by coarse, sclerotic bony septa. Radiograph: A dental periapical X-ray showing the roots of teeth with multiple small, radiolucent cyst-like structures located superior to the root apices. The lesion exhibits coarse sclerotic cortical margins separating the lucent areas, consistent with the presentation of recurrent ameloblastoma. 1.1.2 UNICYSTIC AMELOBLASTOMA | Definition | An intraosseous ameloblastoma with a single cyst cavity. | | :--- | :--- | | **Subtypes** | Luminal; Intra-luminal; Mural | | **Prevalence** | 5-22% of all ameloblastomas | | **Age** | 50% are diagnosed in 2^nd decade of life<br>Mean age<br> = 16 years for cases associated with impacted tooth<br> = 35 years in absence of impacted tooth<br>Range = 1-79 years | | **Gender** | Slight M>F<br>But F more likely to have UAM not associated with impacted tooth | | **Aetiology** | Dysregulated MAPK signaling pathways, with BRAF p.V600E the most common activating mutation in all subtypes | | **Clinical features** | An asymptomatic jaw swelling |  | **Definition** | An intraosseous ameloblastoma with a single cyst cavity. | |---|---| | **Subtypes** | Luminal; Intra-luminal; Mural | |---|---| | **Prevalence** | 5-22% of all ameloblastomas | |---|---| | **Age** | 50% are diagnosed in 2nd decade of life Mean age - = 16 years for cases associated with impacted tooth - = 35 years in absence of impacted tooth Range = 1-79 years | |---|---| | **Gender** | Slight M>F But F more likely to have UAM not associated with impacted tooth | |---|---| | **Aetiology** | Dysregulated MAPK signaling pathways, with BRAF p.V600E the most common activating mutation in all subtypes | |---|---| | **Clinical features** | An asymptomatic jaw swelling | |---|---| A two-column table with a blue header column listing attributes (Definition, Subtypes, Prevalence, Age, Gender, Aetiology, Clinical features) and corresponding descriptive text in the right column regarding unicystic ameloblastoma. 1.1.2 UNICYSTIC AMELOBLASTOMA | Location | Md: 3rd molar & ascending ramus > body > symphysis<br>Most Mx cases occur in posterior areas<br>May also be found in inter-radicular or periapical locations & edentulous areas | | :--- | :--- | | **Periphery/ Shape** | Well-defined, corticated<br>Scalloped outline (for cases unrelated to an impacted tooth) |    | **Location** | Md: 3rd molar & ascending ramus > body > symphysis Most Mx cases occur in posterior areas May also be found in inter-radicular or periapical locations & edentulous areas | |---|---| | **Periphery/ Shape** | Well-defined, corticated Scalloped outline (for cases unrelated to an impacted tooth) | |---|---| A two-row table with a blue left column and light blue right column. The rows are labeled 'Location' and 'Periphery/Shape', providing descriptive characteristics for the condition discussed in the slide. Radiograph: A dental X-ray showing the mandibular teeth, including posterior molars and premolars with visible root structures. Several teeth in the lower jaw exhibit bright white linear densities within their roots, consistent with endodontic filling material (root canal treatment). The image illustrates the appearance of treated teeth and surrounding bone structure. Radiograph: A dental X-ray showing the posterior mandible with a well-defined, corticated radiolucent lesion located in the area of the third molar and ascending ramus. The lesion appears to be associated with an impacted tooth, consistent with the presentation of a unicystic ameloblastoma. 1.1.2 UNICYSTIC AMELOBLASTOMA | Internal Features | Unilocular radiolucency<br>Often associated with UE tooth (most often Mand 8s) | | :--- | :--- | | Surrounding Features | Root resorption<br>Cortical perforation in 1/3 of cases | White & Pharoah, 2014 WHO, 2022    | **Internal Features** | Unilocular radiolucency Often associated with UE tooth (most often Mand 8s) | |---|---| | **Surrounding Features** | Root resorption Cortical perforation in 1/3 of cases | |---|---| *White & Pharoah, 2014* *WHO, 2022* - ==Apparent septa may represent residual bone rather than true septa==. - ==Radicular cyst, particularly when the lesion is located periapically==. - ==Recurrence may result from incomplete excision when the lesion has been mistaken for a cyst==. A two-row table with blue header cells on the left and light-blue content cells on the right. The first row lists 'Internal Features' alongside 'Unilocular radiolucency' and 'Often associated with UE tooth (most often Mand 8s)'. The second row lists 'Surrounding Features' alongside 'Root resorption' and 'Cortical perforation in 1/3 of cases'. A panoramic radiograph showing the posterior mandible with a large, well-defined unilocular radiolucency surrounding the crown of an impacted tooth. The lesion displaces the unerupted tooth inferiorly and appears to cause root resorption on the adjacent erupted molar. A dental radiograph showing a large, unilocular radiolucency in the posterior mandible associated with an impacted tooth. The lesion surrounds the crown of the unerupted third molar and extends superiorly towards the maxilla. 1.1.2 UNICYSTIC AMELOBLASTOMA HISTOPATHOLOGY * Single cyst lined by epithelium with palisaded columnar basal layer with reverse polarity and stellate reticulum-like upper layers in most of the lining constitutes the luminal subtype * Additional plexiform epithelial masses may extend into the lumen only, constituting the intra-luminal type * Additional islands of epithelium extending into the wall constitute the mural subtype * 50-66% of UAM may have a mural component $\rightarrow$ behave more aggressively like conventional ameloblastomas * Extensive sampling is required for accurate definition of subtype * Similar but focal changes may be seen in dentigerous and radicular cysts, especially in areas of inflammation Fig. 1. Histologic types 1. Group 1 – cyst lined by variable, often nondescript, epithelium with no infiltration into fibrous cyst wall. 2. Group 2 – cyst showing intraluminal plexiform epithelial proliferation with no infiltration. 3. Group 3 – cyst with invasion of epithelium into the cyst wall in either (a) a follicular or (b) a plexiform pattern.     #### Histopathology - Single cyst lined by epithelium with palisaded columnar basal layer with reverse polarity and stellate reticulum-like upper layers in most of the lining constitutes the luminal subtype - Additional plexiform epithelial masses may extend into the lumen only, constituting the intra-luminal type - Additional islands of epithelium extending into the wall constitute the mural subtype - 50-66% of UAM may have a mural component → behave more aggressively like conventional ameloblastomas - Extensive sampling is required for accurate definition of subtype - Similar but focal changes may be seen in dentigerous and radicular cysts, especially in areas of inflammation Fig. 1. Histologic types 1. Group 1 – cyst lined by variable, often nondescript, epithelium with no infiltration into fibrous cyst wall. 2. Group 2 – cyst showing intraluminal plexiform epithelial proliferation with no infiltration. 3. Group 3 – cyst with invasion of epithelium into the cyst wall in either (a) a follicular or (b) a plexiform pattern. This is a labelled histologic diagram illustrating the luminal subtype of unicystic ameloblastoma. It depicts a single cyst lined by epithelium with no infiltration into the surrounding fibrous wall, corresponding to 'Group 1' in the figure key. A schematic cross-section of a cyst showing a fibrous wall lined by epithelium with a plexiform epithelial proliferation extending into the lumen. The slide text identifies this as Group 2, representing the intra-luminal subtype of unicystic ameloblastoma where additional plexiform epithelial masses extend into the lumen only. This is a schematic diagram illustrating the mural subtype of a unicystic ameloblastoma. It depicts a cyst cavity lined by epithelium, with islands of neoplastic epithelial cells extending into and infiltrating the surrounding fibrous connective tissue wall. A labelled histological diagram showing a cyst lined by epithelium with an intraluminal proliferation of plexiform epithelial masses extending into the fibrous wall. This illustrates Group 3b, defined in the text as a cyst with invasion of epithelium into the cyst wall in a plexiform pattern. # 1.1.2 UNICYSTIC AMELOBLASTOMA **DIFFERENTIAL DIAGNOSIS** * May be indistinguishable from a dentigerous cyst or odontogenic keratocyst * Histopathologic correlation required for definitive diagnosis **MANAGEMENT/PROGNOSIS/RECURRENCE** * Up to 30% may recur after enucleation, as definitive diagnosis prior to initial treatment is not possible * Conservative marsupialisation followed by enucleation is proposed for luminal and intraluminal UAM * Risk of recurrence so long-term follow up required * Mural UAM appears to be intermediate between UAM and conventional ameloblastoma * Might require consideration of more extensive surgery as for conventional ameloblastoma, depending on size, extent of intra-mural proliferation and radiological findings * However, accurate diagnosis often only follows definitive removal, allowing a period of follow up to confirm recurrence before more aggressive treatment. #### Differential Diagnosis - May be indistinguishable from a dentigerous cyst or odontogenic keratocyst - Histopathologic correlation required for definitive diagnosis #### Management/Prognosis/Recurrence - Up to 30% may recur after enucleation, as definitive diagnosis prior to initial treatment is not possible - Conservative marsupialisation followed by enucleation is proposed for luminal and intraluminal UAM - Risk of recurrence so long-term follow up required - Mural UAM appears to be intermediate between UAM and conventional ameloblastoma - Might require consideration of more extensive surgery as for conventional ameloblastoma, depending on size, extent of intra-mural proliferation and radiological findings - However, accurate diagnosis often only follows definitive removal, allowing a period of follow up to confirm recurrence before more aggressive treatment. 1.2 ADENOMATOID ODONTOGENIC TUMOUR | Definition | A benign encapsulated epithelial odontogenic tumour that contains rosette or duct-like structures and has an indolent behaviour. | | :--- | :--- | | Prevalence | <10% of all odontogenic tumours | | Age | Wide age range, but >80% are diagnosed in the 2nd and 3rd decades of life | | Gender | F>M; 2:1 | | Aetiology | • Unknown, although KRAS p.G12V and p.G12R mutations are detected in approximately 70% of sporadic AOTs<br>• Multiple AOTs can occur in Schimmelpenning syndrome | | Clinical Features | • Most are asymptomatic<br>• All have limited growth potential<br>• Large AOTs present as bony hard swellings with cortical expansion but not perforation<br>• Peripheral AOTs appear as small gingival nodules | WHO, 2022   #### Definition A benign encapsulated epithelial odontogenic tumour that contains rosette or duct-like structures and has an indolent behaviour. #### Prevalence <10% of all odontogenic tumours #### Age Wide age range, but >80% are diagnosed in the 2nd and 3rd decades of life #### Gender F>M; 2:1 #### Aetiology - Unknown, although KRAS p.G12V and p.G12R mutations are detected in approximately 70% of sporadic AOTs - Multiple AOTs can occur in Schimmelpenning syndrome #### Clinical Features - Most are asymptomatic - All have limited growth potential - Large AOTs present as bony hard swellings with cortical expansion but not perforation - Peripheral AOTs appear as small gingival nodules *WHO, 2022* A two-column table summarizing the key characteristics of Adenomatoid Odontogenic Tumour (AOT), with rows for Definition, Prevalence, Age, Gender, Aetiology, and Clinical Features. Radiograph: A dental panoramic radiograph (orthopantomogram) showing the maxilla and mandible with multiple teeth, including impacted or displaced tooth structures in the upper right quadrant. 1.2 ADENOMATOID ODONTOGENIC TUMOUR | | | | :--- | :--- | | **Location** | 95% intraosseous (Mx>Md, Ant>Post)<br>75% cases are located around or alongside the crown of an UE permanent tooth, often extending apically past CEJ<br><br>5% extraosseous (anterior maxillary gingiva) | | **Periphery** | Well defined, unilocular, symmetric with corticated/sclerotic border | A B C FIGURE 22-27 A-C, Intraoral images of adenomatoid odontogenic tumor (arrows, Fig. A) within the maxilla with various amounts of calcification, some of which have a pebble-like shape. (A, Courtesy R. Howell, DDS, Morgantown, WV.) White & Pharoah, 2014     #### Location - 95% intraosseous (Mx>Md, Ant>Post) - 75% cases are located around or alongside the crown of an UE permanent tooth, often extending apically past CEJ - 5% extraosseous (anterior maxillary gingiva) #### Periphery Well defined, unilocular, symmetric with corticated/sclerotic border *FIGURE 22-27 A-C, Intraoral images of adenomatoid odontogenic tumor (arrows, Fig. A) within the maxilla with various amounts of calcification, some of which have a pebble-like shape. (A, Courtesy R. Howell, DDS, Morgantown, WV.)* *White & Pharoah, 2014* - ==The tumour may expand the follicle and surround most of the tooth.== - ==Unlike a dentigerous cyst, it does not usually attach at the cemento-enamel junction; it tends to surround much of the root and part of the crown.== A radiograph of the maxilla showing a well-defined, unilocular radiolucency surrounding the crown of an unerupted permanent tooth. The lesion contains multiple small, irregular radiopaque foci resembling calcifications or 'pebbles', and white arrows indicate the periphery of the mass. A two-row data table with blue header cells on the left. The first row is labeled 'Location' and lists statistics for intraosseous (95%) and extraosseous (5%) occurrences, including details about tooth association. The second row is labeled 'Periphery' and describes the lesion as well defined, unilocular, symmetric with corticated/sclerotic border. Radiograph: A dental X-ray of the maxilla showing a large, well-defined radiolucent lesion associated with an impacted tooth. The lesion contains scattered radiopaque calcifications, giving it a mixed density appearance. A periapical radiograph (labeled C) showing the maxillary anterior region with a well-defined radiolucent lesion associated with an impacted tooth. The lesion contains scattered radiopaque foci, appearing as 'snowflake' or pebble-like calcifications within the unilocular area. # 1.2 ADENOMATOID ODONTOGENIC TUMOUR | Internal Features | Radiolucent, 2/3^rd of cases show small radiopaque foci – “snowstorm” | | :--- | :--- | | **Surrounding Features** | Tooth displacement frequent<br>Root resorption rare<br>Cortical expansion (perforation rare) | H A B White & Pharoah, 2014 **Extraosseous variant:** * Appears as a unilocular radiolucency located between, above, or superimposed upon the roots of erupted teeth * May cause superficial erosion of the underlying alveolar bone     #### Internal Features Radiolucent, 2/3rd of cases show small radiopaque foci — "snowstorm" #### Surrounding Features - Tooth displacement frequent - Root resorption rare - Cortical expansion (perforation rare) *White & Pharoah, 2014* #### Extraosseous Variant - Appears as a unilocular radiolucency located between, above, or superimposed upon the roots of erupted teeth - May cause superficial erosion of the underlying alveolar bone - ==The peripheral or extraosseous variant is uncommon.== - ==A slightly loosened appearance may occur when the lesion is positioned on the buccal or lingual aspect of the jaw.== A two-row table listing the internal and surrounding radiographic features of an adenomatoid odontogenic tumor. The 'Internal Features' row describes a radiolucent appearance with small radiopaque foci ('snowstorm') in 2/3rd of cases, while the 'Surrounding Features' row notes frequent tooth displacement, rare root resorption, and cortical expansion. Radiograph: A cropped panoramic dental image showing a large, well-defined radiolucent lesion associated with an unerupted tooth in the mandible. The crop corresponds to panel A of the original figure caption, which notes that there are no apparent internal calcifications visible in this view. Radiograph: Two cropped dental images labeled A and B showing an adenomatoid odontogenic tumor within the mandible. Panel A is a panoramic view with no apparent internal calcifications, while Panel B is a cone-beam CT image related to the first premolar, displaying pebble-like calcifications distal to the tooth. A cropped cone-beam CT radiograph (labeled 'B') showing a dental lesion associated with the root of a premolar. The image reveals a radiolucent area containing small, distinct radiopaque foci described as pebble-like calcifications. 1.2 ADENOMATOID ODONTOGENIC TUMOUR HISTOPATHOLOGY * Encapsulated * Contain variably sized nodules of spindle, cuboidal and columnar epithelial odontogenic cells with minimal stroma * Within the nodules are rosette or duct-like structures, which produce the adenomatoid or gland-like appearance * Eosinophilic amorphous secretory material similar to enamel matrix present between the epithelial cells and rosette-like structures * +/- Small foci of calcification, dentinoid matrix, & haemorrhage * +/- cysts lined by non-keratinising stratified epithelium B  #### Histopathology - Encapsulated - Contain variably sized nodules of spindle, cuboidal and columnar epithelial odontogenic cells with minimal stroma - Within the nodules are rosette or duct-like structures, which produce the adenomatoid or gland-like appearance - Eosinophilic amorphous secretory material similar to enamel matrix present between the epithelial cells and rosette-like structures - +/- Small foci of calcification, dentinoid matrix, & haemorrhage - +/- cysts lined by non-keratinising stratified epithelium - ==The cysts may be lined by non-keratinising stratified epithelium resembling a dentigerous cyst.== Histopathology slide showing characteristic duct-like spaces lined by cuboidal to columnar epithelium with nuclei away from the luminal surface. 1.2 ADENOMATOID ODONTOGENIC TUMOUR DIFFERENTIAL DIAGNOSIS • AOT-like areas have been recognized within other odontogenic tumours (inc. odontomas) • AOT may contain areas resembling calcifying epithelial odontogenic tumour with clear cells • These histological overlaps makes radiological and clinical correlation essential for definitive diagnosis. MANAGEMENT • Enucleation (including capsule) PROGNOSIS/RECURRENCE • Almost no risk of recurrence following conservative enucleation. #### Differential Diagnosis - AOT-like areas have been recognized within other odontogenic tumours (inc. odontomas) - AOT may contain areas resembling calcifying epithelial odontogenic tumour with clear cells - These histological overlaps makes radiological and clinical correlation essential for definitive diagnosis. #### Management - Enucleation (including capsule) #### Prognosis/Recurrence - Almost no risk of recurrence following conservative enucleation. - ==Dentigerous cyst.== - ==Odontoma.== - ==Calcifying epithelial odontogenic tumour.== - ==Other lesions containing calcification.== 1.3 SQUAMOUS ODONTOGENIC TUMOUR | Definition | A benign, slow-growing epithelial odontogenic tumour with squamous differentiation. | | :--- | :--- | | Prevalence | Rare | | Age | Wide age distribution (mean age = 34.8 years)<br>Multiple SOTs: younger age group with marked predilection for African Americans | | Gender | M=F | | Aetiology | Unknown but a familial incidence has been reported<br>Thought to originate from rests of Malassez, gingival surface epithelium or remnants of the dental lamina. | | Clinical Features | Asymptomatic swelling<br>Minority are associated with pain, tenderness, mobility of teeth or bone expansion. |  #### Definition A benign, slow-growing epithelial odontogenic tumour with squamous differentiation. #### Prevalence Rare #### Age - Wide age distribution (mean age = 34.8 years) - Multiple SOTs: younger age group with marked predilection for African Americans #### Gender M = F #### Aetiology - Unknown but a familial incidence has been reported - Thought to originate from rests of Malassez, gingival surface epithelium or remnants of the dental lamina. #### Clinical Features - Asymptomatic swelling - Minority are associated with pain, tenderness, mobility of teeth or bone expansion. - ==It may occur in edentulous patients.== A two-column table summarizing the clinical and pathological features of Squamous Odontogenic Tumour (SOT). The left column lists categories including Definition, Prevalence, Age, Gender, Aetiology, and Clinical Features, while the right column provides corresponding details such as 'Rare', 'M=F', and origin from rests of Malassez. 1.3 SQUAMOUS ODONTOGENIC TUMOUR | Location | Tooth bearing parts of the jaw (Mx = Md) <br> • Ant Mx & Post Md more common <br> Multifocal or extraosseous lesions have been reported (rare) | | :--- | :--- | | Periphery/ Shape | Triangular or semi-circular <br> Unilocular, well-defined +/- cortication <br> Multilocularity reported for larger and extensive lesions | | Internal Features | Radiolucent | | Surrounding Features | Most lesions show continuity with 1+ tooth roots <br> Root displacement common. <br> Root resorption rare. <br><br> Peripheral variant may cause saucerisation (due to pressure, not infiltration) |   #### Location - Tooth bearing parts of the jaw (Mx = Md) - Ant Mx & Post Md more common - Multifocal or extraosseous lesions have been reported (rare) #### Periphery / Shape - Triangular or semi-circular - Unilocular, well-defined +/- cortication - Multilocularity reported for larger and extensive lesions #### Internal Features Radiolucent #### Surrounding Features - Most lesions show continuity with 1+ tooth roots - Root displacement common. - Root resorption rare. - Peripheral variant may cause saucerisation (due to pressure, not infiltration) - ==Most lesions are solitary.== - ==Multilocular or more aggressive lesions may produce cortical expansion or perforation.== A structured table with a blue left-hand column listing categories (Location, Periphery/Shape, Internal Features, Surrounding Features) and corresponding text descriptions of radiographic features in the right-hand column. Radiograph: A dental panoramic X-ray showing the posterior region of the mandible. It depicts a well-defined, radiolucent lesion situated between the roots of the molars and premolars, consistent with the appearance of an odontogenic tumour. # 1.3 SQUAMOUS ODONTOGENIC TUMOUR ## HISTOPATHOLOGY * Islands of bland well-differentiated squamous epithelium in a fibrous or myxoid stroma * Peripheral cells of the islands are flat to cuboidal with very infrequent mitoses * Central cells have a tendency for cystic degeneration, individual cell keratinization, and calcification * +/- Mucous metaplasia, sebaceous differentiation, and ghost cell-like areas  #### Histopathology - Islands of bland well-differentiated squamous epithelium in a fibrous or myxoid stroma - Peripheral cells of the islands are flat to cuboidal with very infrequent mitoses - Central cells have a tendency for cystic degeneration, individual cell keratinization, and calcification - +/- Mucous metaplasia, sebaceous differentiation, and ghost cell-like areas A histopathology micrograph showing islands of benign squamous epithelium embedded within a mature fibrous stroma. The peripheral cells of the epithelial islands appear flattened, while the central areas exhibit microcystic degeneration and individual cell keratinization. # 1.3 SQUAMOUS ODONTOGENIC TUMOUR **DIFFERENTIAL DIAGNOSIS** * Ameloblastoma – acanthomatous or desmoplastic variants * SOT lacks peripheral columnar cells & palisading nuclei * Well-differentiated squamous cell carcinoma * SOT lacks peripheral palisading with reverse nuclear polarity, and the cytological features are bland (i.e. no dysplasia) * SOT-like proliferation of epithelium may develop in the lining of odontogenic cysts **MANAGEMENT** * Enucleation **PROGNOSIS/RECURRENCE** * Unifocal SOT rarely recurs after conservative surgery. * Multifocal or recurring SOT, especially of the maxilla, may require a more radical approach. #### Differential Diagnosis - Ameloblastoma – acanthomatous or desmoplastic variants - SOT lacks peripheral columnar cells & palisading nuclei - Well-differentiated squamous cell carcinoma - SOT lacks peripheral palisading with reverse nuclear polarity, and the cytological features are bland (i.e. no dysplasia) - SOT-like proliferation of epithelium may develop in the lining of odontogenic cysts #### Management - Enucleation #### Prognosis / Recurrence - Unifocal SOT rarely recurs after conservative surgery. - Multifocal or recurring SOT, especially of the maxilla, may require a more radical approach. - ==Well-differentiated squamous cell carcinoma is particularly considered when there is no corticated border.== - ==A solitary unilocular lesion is generally treated by simple enucleation.== 1.4 CALCIFYING EPITHELIAL ODONTOGENIC TUMOUR | Definition | A benign epithelial odontogenic tumour characterised by amyloid, which may calcify. | | :--- | :--- | | Synonyms | Pindborg tumour | | Prevalence | Rare | | Age | Wide age range (8-83 years)<br>Maximum incidence in the 4th decade | | Gender | M=F | | Aetiology | Unknown (mutations in tumour suppressor genes and oncogenes have been reported) | | Clinical Features | Asymptomatic<br>Larger lesions cause slow growing, localised expansion of the jaw + tooth mobility |  | Feature | Details | | :--- | :--- | | Definition | A benign epithelial odontogenic tumour characterised by amyloid, which may calcify. | | Synonyms | Pindborg tumour | | Prevalence | Rare | | Age | Wide age range (8–83 years); maximum incidence in the 4th decade | | Gender | M = F | | Aetiology | Unknown (mutations in tumour suppressor genes and oncogenes have been reported) | | Clinical Features | Asymptomatic; larger lesions cause slow growing, localised expansion of the jaw + tooth mobility | > [!note] Lecturer — Alternative Name > The tumour was also referred to as a “pinball tumour.” A two-column table summarizing key clinical and pathological features of Calcifying Epithelial Odontogenic Tumour (Pindborg tumour). The left column lists categories including Definition, Synonyms, Prevalence, Age, Gender, Aetiology, and Clinical Features, while the right column provides corresponding details such as its characterization by amyloid, rarity, age range of 8-83 years, equal gender distribution, unknown aetiology, and asymptomatic presentation. 1.4 CALCIFYING EPITHELIAL ODONTOGENIC TUMOUR | Location | 85% intraosseous, tooth-bearing areas of jaws (Md>Mx)<br>Md body most common<br>50% are associated with UE teeth<br>15% extraosseous | | :--- | :--- | | **Periphery/**<br>**Shape** | Unilocular (70%) > Multilocular (30%)<br>Variable definition and cortication | White & Pharoah, 2014    | Location | 85% intraosseous, tooth-bearing areas of jaws (Md > Mx); Md body most common; 50% are associated with UE teeth; 15% extraosseous | | :--- | :--- | | Periphery/Shape | Unilocular (70%) > Multilocular (30%); variable definition and cortication | *White & Pharoah, 2014* > [!note] Lecturer — Mandibular Distribution > Approximately 60% of tumours occur in the mandible, with a predilection for the mandibular body. A table listing clinical characteristics such as location and periphery/shape with associated statistics. A cropped radiograph showing a mixed radiolucent-radiopaque lesion in the mandible, indicated by white arrows. The image demonstrates the characteristic appearance of a calcifying odontogenic tumor associated with an unerupted tooth. Radiograph: A panoramic dental X-ray (labeled 'B') showing a large mixed radiolucent-radiopaque lesion in the posterior mandible. The lesion exhibits a characteristic 'driven snow' or scattered calcific appearance and is associated with an impacted tooth at its inferior border. 1.4 CALCIFYING EPITHELIAL ODONTOGENIC TUMOUR | Internal Features | 75% mixed radiolucent/radiopaque <br> • Classic “driven snow” appearance <br> • May be crescent/donut shaped <br> • **Radiopacities close to crown of embedded tooth** <br> • Degree of calcification correlates with age of lesion <br> <br> Remaining 25% CEOTs are radiolucent (but totally radiopaque lesions are also seen) | | :--- | :--- | | Surrounding Features | May displace teeth or prevent its eruption <br> Expansion of jaw (without perforation) | WHO, 2022   | Internal Features | 75% mixed radiolucent/radiopaque: - Classic "driven snow" appearance - May be crescent/donut shaped - Radiopacities close to crown of embedded tooth - Degree of calcification correlates with age of lesion Remaining 25% CEOTs are radiolucent (but totally radiopaque lesions are also seen) | | :--- | :--- | | Surrounding Features | May displace teeth or prevent its eruption; expansion of jaw (without perforation) | *WHO, 2022* - ==The opacities may be embedded around the crown of an unerupted tooth== A two-row table summarizing the radiographic and clinical features of a lesion, divided into 'Internal Features' (describing mixed radiolucent/radiopaque patterns like 'driven snow') and 'Surrounding Features' (describing effects on teeth and jaw expansion). Radiograph: A cropped dental radiograph showing the posterior mandible with an impacted third molar. The image illustrates a lesion associated with the crown of the embedded tooth, appearing as mixed radiolucent and radiopaque areas (calcifications) that correspond to the 'driven snow' appearance described in the text. 1.4 CALCIFYING EPITHELIAL ODONTOGENIC TUMOUR HISTOPATHOLOGY • Variable appearance with 4 subtypes: • Clear cell • Cystic/microcystic • Non-calcifying/Langerhans cell rich • AOT subtype • Comprise sheets, cords or nests of polyhedral epithelial cells with distinct cell borders and prominent intercellular bridges • +/- nuclear pleomorphism (mitoses are rare) • Deposits of amorphous lightly eosinophilic amyloid composed of ameloblast-associated proteins (stains with Congo red) • These may calcify forming large masses or small round concentric densely basophilic calcifications with Liesegang rings Congo Red stain demonstrating the amyloid material. (WHO, 2022)   #### Histopathology - Variable appearance with 4 subtypes: - Clear cell - Cystic/microcystic - Non-calcifying/Langerhans cell rich - AOT subtype - Comprise sheets, cords or nests of polyhedral epithelial cells with distinct cell borders and prominent intercellular bridges - +/- nuclear pleomorphism (mitoses are rare) - Deposits of amorphous lightly eosinophilic amyloid composed of ameloblast-associated proteins (stains with Congo red) - These may calcify forming large masses or small round concentric densely basophilic calcifications with Liesegang rings *Congo Red stain demonstrating the amyloid material. (WHO, 2022)* - ==Amyloid deposits occur between the epithelial cells== This is a histopathology micrograph showing islands of odontogenic epithelium embedded in a stroma, accompanied by amorphous eosinophilic amyloid deposits and focal calcifications. The tissue is stained with hematoxylin and eosin (H&E), revealing distinct cellular nests against the pink background material. A micrograph showing a histological section stained with Congo red, where amorphous deposits of amyloid material appear as salmon-pink or orange-red patches against a background of blue-stained nuclei and pale fibrous stroma. A scale bar in the lower left corner indicates 200µm. # 1.4 CALCIFYING EPITHELIAL ODONTOGENIC TUMOUR **DIFFERENTIAL DIAGNOSIS** * May extend into adjacent medullary spaces in an infiltrative pattern worrying for malignancy * Foci resembling CEOT may be found in odontomas and the follicles of unerupted teeth **MANAGEMENT** * Local surgical removal **PROGNOSIS/RECURRENCE** * Recurrence rate = approx. 13% * Varies with treatment modality, being much higher in those treated by curettage * No histological parameters predict recurrence * Malignant transformation rare #### Differential Diagnosis - May extend into adjacent medullary spaces in an infiltrative pattern worrying for malignancy - Foci resembling CEOT may be found in odontomas and the follicles of unerupted teeth #### Management - Local surgical removal #### Prognosis/Recurrence - Recurrence rate = approx. 13% - Varies with treatment modality, being much higher in those treated by curettage - No histological parameters predict recurrence - Malignant transformation rare > [!note] Lecturer — Radiological Correlation > The relationship between crescent- or donut-shaped opacities and the crown of an unerupted tooth can help distinguish this tumour from other mixed-density lesions. > > - Histopathological findings should be correlated with radiological and clinical features. - ==More aggressive treatment is associated with less recurrence== - ==Odontomas may also interfere with tooth eruption.== PART 2: BENIGN EPITHELIAL & MESENCHYMAL ODONTOGENIC TUMOURS 1. Odontoma 2. Ameloblastic fibroma 3. Primordial odontogenic tumour 4. Dentinogenic ghost cell tumour 1. Odontoma 2. Ameloblastic fibroma 3. Primordial odontogenic tumour 4. Dentinogenic ghost cell tumour 2.1 ODONTOMA | **Definition** | Mixed odontogenic hamartomas that mature from soft tissue to predominantly dental hard tissues with a small amount of residual odontogenic epithelium and ectomesenchyme | | :--- | :--- | | **Subtypes** | Compound; Complex | | **Prevalence** | Most common odontogenic tumour (some consider it to be a hamartoma) | | **Age** | 2nd and 3rd decades | | **Gender** | M=F | | **Aetiology** | Unknown, genetic mutation of tooth germ is possible factor | | **Clinical Features** | Frequently associated with UE tooth<br>Asymptomatic (unless secondarily infected) |  #### Definition Mixed odontogenic hamartomas that mature from soft tissue to predominantly dental hard tissues with a small amount of residual odontogenic epithelium and ectomesenchyme. #### Subtypes - Compound - Complex #### Prevalence Most common odontogenic tumour (some consider it to be a hamartoma). #### Age 2nd and 3rd decades. #### Gender M = F #### Aetiology Unknown; genetic mutation of tooth germ is a possible factor. #### Clinical Features - Frequently associated with an unerupted tooth - Asymptomatic (unless secondarily infected) This is a two-column data table outlining the clinical and pathological characteristics of an odontoma. The rows list specific attributes including Definition, Subtypes (Compound; Complex), Prevalence, Age, Gender, Aetiology, and Clinical Features. 2.1 ODONTOMA | Location | Any tooth-bearing area; typically between roots or superior to crowns<br>*Compound*: Mx ant<br>*Complex*: Md post > Mx ant<br>May be multiple | | :--- | :--- | | **Periphery/**<br>**Shape** | Well-defined with lucent band and adjacent corticated periphery<br>Typically 10-30mm (up to 80mm has been reported) | | **Internal**<br>**Features** | *Early stage*: RL with focal areas of calcification<br>*Compound*: numerous tooth-like structures (denticles)<br>*Complex*: disorganised mass of calcified tissue | | **Surrounding**<br>**Features** | Associated with an unerupted tooth<br>Expansion of jaw (larger lesions) |    #### Location - Any tooth-bearing area; typically between roots or superior to crowns - *Compound*: maxillary anterior - *Complex*: mandibular posterior > maxillary anterior - May be multiple #### Periphery / Shape - Well-defined with a lucent band and adjacent corticated periphery - Typically 10–30 mm (up to 80 mm has been reported) #### Internal Features - *Early stage*: radiolucency with focal areas of calcification - *Compound*: numerous tooth-like structures (denticles) - *Complex*: disorganised mass of calcified tissue #### Surrounding Features - Associated with an unerupted tooth - Expansion of the jaw (larger lesions) A four-row informational table summarizing the radiographic and clinical features of odontomas. The left column lists categories including Location, Periphery/Shape, Internal Features, and Surrounding Features, with corresponding descriptive text in the right column. A dental radiograph showing the maxillary teeth and surrounding bone structure, with a focus on an area between the roots or superior to the crowns where an odontoma may be present. The image highlights well-defined structures that could represent tooth-like formations (denticles) typical of a compound odontoma. Radiograph: A dental X-ray showing a large, irregular radiopaque mass located posteriorly in the jaw (likely mandible), associated with an unerupted tooth. The lesion appears as a disorganised calcified structure, consistent with the complex odontoma described in the table. 2.1 ODONTOMA HISTOPATHOLOGY Compound odontoma: contains multiple rudimentary teeth exhibiting dentin and enamel matrix. Dentine in odontomas usually shows some irregularity of tubule structure. Complex odontoma: consists of a disorganized mass of mature tubular dentine intermixed with rounded zones of enamel matrix where enamel has been lost on decalcification, with areas of dental pulp and cementum. MANAGEMENT Local surgical removal PROGNOSIS/RECURRENCE Do not recur (unless incomplete removal) WHO, 2022   #### Histopathology - **Compound odontoma:** contains multiple rudimentary teeth exhibiting dentin and enamel matrix. Dentine in odontomas usually shows some irregularity of tubule structure. - **Complex odontoma:** consists of a disorganized mass of mature tubular dentine intermixed with rounded zones of enamel matrix where enamel has been lost on decalcification, with areas of dental pulp and cementum. #### Management Local surgical removal. #### Prognosis / Recurrence Do not recur (unless removal is incomplete). *WHO, 2022* A histopathology micrograph showing multiple discrete, rounded masses of eosinophilic tissue (dentin) surrounded by thin basophilic rims (enamel matrix), consistent with the description of a compound odontoma containing rudimentary teeth. A histopathology micrograph showing a disorganized mass of mature tubular dentine (stained pink) intermixed with rounded zones of enamel matrix (clear/white areas), consistent with the description of a complex odontoma. # 2.2 AMELOBLASTIC FIBROMA (AF) | | | | :--- | :--- | | **Definition** | A rare, benign, mixed odontogenic tumour comprising cellular mesenchymal tissue resembling dental papilla and an epithelial component resembling early developing enamel organ, without dental hard tissue or matrix. | | **Prevalence** | 2% of all odontogenic tumours | | **Age** | Mean = 15 years<br>Range = 7 weeks – 61 years<br>80% occur <22 years (before end of odontogenesis) | | **Gender** | M>F; 1.4:1 | | **Aetiology** | Unclear, but BRAF p.V600E mutations in 46% of cases | | **Clinical Features** | Asymptomatic, slow-growing jawbone expansion (78%) |  #### Definition A rare, benign, mixed odontogenic tumour comprising cellular mesenchymal tissue resembling dental papilla and an epithelial component resembling early developing enamel organ, without dental hard tissue or matrix. #### Clinical Profile - **Prevalence:** 2% of all odontogenic tumours - **Age:** - Mean = 15 years - Range = 7 weeks – 61 years - 80% occur <22 years (before end of odontogenesis) - **Gender:** M>F; 1.4:1 - **Aetiology:** Unclear, but BRAF p.V600E mutations in 46% of cases - **Clinical features:** Asymptomatic, slow-growing jawbone expansion (78%) A two-column table presenting key clinical and pathological characteristics of Ameloblastic Fibroma, including rows for Definition, Prevalence, Age, Gender, Aetiology, and Clinical Features. # 2.2 AMELOBLASTIC FIBROMA | | | | :--- | :--- | | **Location** | Mand>Max; 3:1<br>Post (82%) > Ant (~10%)<br>Common locations:<br>• At crest of alveolar ridge<br>• Follicular relationship with UE tooth (occlusal to tooth)<br>• Where a tooth has failed to develop | | **Periphery/ Shape** | Well-defined<br>Corticated | | **Internal Features** | Unilocular (60%) – totally radiolucent<br>Multilocular (large) – indistinct curved septa<br>80% associated with an impacted tooth (usually 6s or 7s) | | **Surrounding Features** | Tooth displacement (resorption uncommon)<br>• Typically in apical direction<br>• Tooth may be inhibited from eruption<br>Jaw expansion (perforation uncommon) | White & Pharoah, 2014     #### Location - Mand>Max; 3:1 - Posterior (82%) > Anterior (~10%) - Common locations: - At crest of alveolar ridge - Follicular relationship with unerupted tooth (occlusal to tooth) - Where a tooth has failed to develop #### Radiographic Features - **Periphery/Shape:** Well-defined; corticated - **Internal features:** - Unilocular (60%) – totally radiolucent - Multilocular (large) – indistinct curved septa - 80% associated with an impacted tooth (usually 6s or 7s) - **Surrounding features:** - Tooth displacement (resorption uncommon) - Typically in apical direction - Tooth may be inhibited from eruption - Jaw expansion (perforation uncommon) *White & Pharoah, 2014* > [!note] Lecturer — Cortical Perforation > Cortical perforation is relatively uncommon because the slow growth of ameloblastic fibroma permits periosteal new bone formation. A four-row, two-column table summarizing the radiographic and clinical features of ameloblastic fibroma. The left column lists categories (Location, Periphery/Shape, Internal Features, Surrounding Features), while the right column provides corresponding details such as mandibular predominance, well-defined corticated borders, unilocular or multilocular appearance, association with impacted teeth, and tooth displacement. A panoramic dental radiograph (labeled 'A') showing the posterior mandible with a white arrow pointing to a well-defined, corticated radiolucent lesion associated with an impacted tooth. Radiograph: A lateral jaw radiograph showing a large, well-defined multilocular radiolucent lesion in the posterior mandible. The lesion contains distinct curved septa and is associated with an impacted tooth displaced inferiorly within the radiolucency. A dental radiograph showing a large, well-defined multilocular radiolucency in the posterior mandible. The lesion contains multiple rounded radiopaque structures resembling developing tooth crowns and is associated with displaced teeth. # 2.2 AMELOBLASTIC FIBROMA DIFFERENTIAL DIAGNOSIS | | | | :--- | :--- | | **Hyperplastic follicle** | Difficult to differentiate from small AF | | **Dentigerous cyst** | Difficult to differentiate from small AF<br>Less likely to be DC if margins not at CEJ or at root surface within 2-3mm of CEJ | | **OKC** | Minimal expansion for size, internally lucent, only a few septa when large | | **Ameloblastoma** | Coarser septa than AF (AF septa are infrequent & fine)<br>Substantial root resorption is a feature<br>Older age group | | **Central giant cell granuloma** | Epicentre anterior to 6s<br>Characteristically granular & ill-defined septa<br>Tendency for substantial root resorption<br>Typically lobulated expansion | | **Aneurysmal bone cyst** | Extremely expansile, unless small; MRI shows fluid-fluid levels | | **Odontogenic myxoma** | Straight septa<br>Limited expansion for size<br>Older age group |  #### Differential Diagnosis - **Hyperplastic follicle** — Difficult to differentiate from small AF - **Dentigerous cyst** — Difficult to differentiate from small AF; less likely to be DC if margins not at CEJ or at root surface within 2-3mm of CEJ - **OKC** — Minimal expansion for size, internally lucent, only a few septa when large - **Ameloblastoma** — - Coarser septa than AF (AF septa are infrequent & fine) - Substantial root resorption is a feature - Older age group - **Central giant cell granuloma** — - Epicentre anterior to 6s - Characteristically granular & ill-defined septa - Tendency for substantial root resorption - Typically lobulated expansion - **Aneurysmal bone cyst** — Extremely expansile, unless small; MRI shows fluid-fluid levels - **Odontogenic myxoma** — Straight septa; limited expansion for size; older age group A two-column table listing differential diagnoses for ameloblastic fibroma, with conditions such as Hyperplastic follicle and Dentigerous cyst on the left and their distinguishing radiographic or clinical features on the right. 2.2 AMELOBLASTIC FIBROMA HISTOPATHOLOGY * *Mesenchymal component:* myxoid and evenly hypercellular; resembles the dental papilla of the tooth bud * *Epithelial component:* forms long narrow cords and strands of bilaminar cuboidal to columnar palisaded cells with occasional thickenings * No dental hard tissue is normally present but extensive sampling may reveal small foci MANAGEMENT/PROGNOSIS/RECURRENCE * 19% recurrence with conservative removal * Extensive, destructive and recurrent tumours should be treated radically. * Rare sarcomatous transformation  #### Histopathology - *Mesenchymal component:* myxoid and evenly hypercellular; resembles the dental papilla of the tooth bud - *Epithelial component:* forms long narrow cords and strands of bilaminar cuboidal to columnar palisaded cells with occasional thickenings - No dental hard tissue is normally present but extensive sampling may reveal small foci #### Management, Prognosis and Recurrence - 19% recurrence with conservative removal - Extensive, destructive and recurrent tumours should be treated radically - Rare sarcomatous transformation > [!note] Lecturer — Mesenchymal Component > The mesenchymal component was described as a myxoid, evenly hypocellular matrix resembling the dental papilla. Histopathology slide showing a myxoid and evenly hypercellular mesenchymal component resembling the dental papilla of the tooth bud. AMELOBLASTIC FIBRO-ODONTOMA (AFO) | Definition | A benign mixed odontogenic tumour involving ectomesenchymal tissues with the presence of enamel & dentine, demonstrating histological features of ameloblastic fibroma & complex odontoma. <br> ~Atlas of Oral & Maxillofacial Radiology, 2017 | | :--- | :--- | | **Age** | Identified 1^st & 2^nd decades of life | | **Gender** | M=F | | **Clinical features** | Slow growing, expansile<br>Often interrupts tooth eruption<br>Often associated with missing tooth |  #### Definition A benign mixed odontogenic tumour involving ectomesenchymal tissues with the presence of enamel & dentine, demonstrating histological features of ameloblastic fibroma & complex odontoma. *~ Atlas of Oral & Maxillofacial Radiology, 2017* #### Clinical Presentation - **Age:** Identified in the 1st & 2nd decades of life - **Gender:** M = F - **Clinical features:** - Slow growing, expansile - Often interrupts tooth eruption - Often associated with missing tooth > [!note] Lecturer — AFO Classification > Ameloblastic fibro-odontoma is not officially recognised by the WHO as a separate lesion. Its status remains debated: it may represent an intermediate lesion, an ameloblastic fibroma containing hard tissue, or a separate entity. Its classification as a developing stage of an odontoma has been questioned because it may show BRAFpV600E mutation, locally aggressive behaviour and neoplastic recurrence. A two-column table summarizing key clinical and pathological features of Ameloblastic Fibro-Odontoma (AFO). The rows define the condition, age of identification (1st & 2nd decades), gender prevalence (M=F), and clinical characteristics such as slow growth and association with missing teeth. # AMELOBLASTIC # FIBRO-ODONTOMA | Location | Md > Mx<br>Post > Ant<br>Majority within alveolar process, often approximating alveolar crest<br>Epicentre often occlusal to tooth or towards alveolar crest | | :--- | :--- | | **Periphery/**<br>**Shape** | Well defined, corticated | | **Internal**<br>**Features** | RL/RO<br>Most often associated with an impacted tooth<br>Majority of lesion is RL – with some calcifications<br>May appear like donut (radiopaque enamel-like margin) or tooth-like structures<br>(Small) enlarged follicles with 1-2 discrete RO<br>(Large) More extensive calcified internal structure | | **Surrounding**<br>**Features** | Tooth displacement<br>Impedes the eruption of involved tooth |      #### Radiographic Features - **Location:** - Md > Mx - Posterior > Anterior - Majority within the alveolar process, often approximating the alveolar crest - Epicentre often occlusal to the tooth or towards the alveolar crest - **Periphery/Shape:** - Well defined, corticated - **Internal Features:** - RL/RO - Most often associated with an impacted tooth - Majority of the lesion is RL — with some calcifications - May appear like a donut (radiopaque enamel-like margin) or tooth-like structures - (Small) enlarged follicles with 1–2 discrete RO - (Large) more extensive calcified internal structure - **Surrounding Features:** - Tooth displacement - Impedes the eruption of the involved tooth A two-column table listing radiographic features of ameloblastic fibro-odontoma, including location, periphery/shape, internal features, and surrounding characteristics. Radiograph: A dental panoramic X-ray showing developing teeth in the jaw, with a white arrow pointing to a small radiopaque structure located between the roots of an erupted tooth and an unerupted tooth bud. Radiograph: A dental X-ray image showing multiple teeth in the posterior jaw, including impacted molars with developing roots. The image illustrates a radiolucent area associated with an impacted tooth that contains discrete radiopaque calcifications, consistent with the features of an ameloblastic fibro-odontoma. Radiograph: A lateral jaw radiograph showing a large, well-defined radiolucent lesion in the posterior mandible associated with an impacted tooth. An arrow points to a small, discrete radiopaque focus within the lesion. Radiograph: A panoramic dental X-ray showing a large, well-defined radiolucent lesion with internal radiopaque calcifications in the posterior mandible. The lesion surrounds an impacted tooth, illustrating the mixed radiolucent-radiopaque appearance characteristic of an ameloblastic fibro-odontoma. # AMELOBLASTIC FIBRO-ODONTOMA ## DIFFERENTIAL DIAGNOSIS | | | | :--- | :--- | | **AF** | Difficult to differentiate unless internal calcifications present | | **Odontoma** | AFO calcifications tend to be smaller & more diffuse; often large lucent regions within<br>Compound odontoma: usually Mx ant; AFO not organised to resemble teeth<br>Complex odontoma: usually one central mass of disorganised tissue | | **AOT/COC** | More common in Mx anterior | | **CEOT** | Rare | ## HISTOPATHOLOGY * Resembles AF & complex odontoma ## MANAGEMENT/PROGNOSIS/RECURRENCE * Low recurrence with conservative excision & enucleation  #### Differential Diagnosis - **AF:** Difficult to differentiate unless internal calcifications are present - **Odontoma:** - AFO calcifications tend to be smaller & more diffuse; often large lucent regions within - Compound odontoma: usually Mx anterior; AFO is not organised to resemble teeth - Complex odontoma: usually one central mass of disorganised tissue - **AOT/COC:** More common in the Mx anterior - **CEOT:** Rare #### Histopathology - Resembles AF & complex odontoma #### Management/Prognosis/Recurrence - Low recurrence with conservative excision & enucleation A two-column table listing differential diagnoses for ameloblastic fibro-odontoma. The left column contains the diagnostic entities (AF, Odontoma, AOT/COC, CEOT) and the right column provides corresponding descriptive notes on radiographic features and clinical presentation. 2.3 PRIMORDIAL ODONTOGENIC TUMOUR | Definition | A benign tumour composed of variably cellular fibrous tissue with areas similar to dental papilla, surrounded by epithelium resembling the internal epithelium of the enamel organ. | | :--- | :--- | | **Age** | Mean = 11.4 years<br>Range = 2-19 years | | **Gender** | Slight M>F | | **Aetiology** | Unknown | | **Clinical Features** | Asymptomatic, although some produce marked cortical expansion |  | Feature | Details | | :--- | :--- | | Definition | A benign tumour composed of variably cellular fibrous tissue with areas similar to dental papilla, surrounded by epithelium resembling the internal epithelium of the enamel organ. | | Age | Mean = 11.4 years; Range = 2–19 years | | Gender | Slight M>F | | Aetiology | Unknown | | Clinical Features | Asymptomatic, although some produce marked cortical expansion | A two-column table listing key clinical and pathological features of Primordial Odontogenic Tumour, including rows for Definition, Age, Gender, Aetiology, and Clinical Features. 2.3 PRIMORDIAL ODONTOGENIC TUMOUR | Location | Tooth-bearing areas of jaws (Md>Mx) <br> Intraosseous | | :--- | :--- | | Periphery/ Shape | Well-defined <br> Unilocular | | Internal Features | Radiolucent <br> Associated with UE tooth (most commonly Md 8s resulting in pericoronal relationship) | | Surrounding Features | Cortical expansion <br> Tooth displacement and resorption |   | Feature | Details | | :--- | :--- | | Location | Tooth-bearing areas of jaws (Md>Mx); intraosseous | | Periphery/Shape | Well-defined; unilocular | | Internal Features | Radiolucent; associated with UE tooth (most commonly Md 8s, resulting in a pericoronal relationship) | | Surrounding Features | Cortical expansion; tooth displacement and resorption | A two-column table summarizing the radiographic features of Primordial Odontogenic Tumour. The left column lists categories (Location, Periphery/Shape, Internal Features, Surrounding Features) against corresponding descriptive findings in the right column. A dental radiograph showing a large, well-defined unilocular radiolucent lesion in the posterior mandible. The lesion surrounds the crown of an impacted tooth (pericoronal relationship) and is associated with cortical expansion and displacement of adjacent teeth. 2.3 PRIMORDIAL ODONTGENIC TUMOUR HISTOPATHOLOGY - Loose or myxoid fibrous tissue with variable numbers of fusiform and stellate fibroblasts, with areas of cellular odontogenic mesenchyme - Periphery is covered by a single layer of columnar or cuboidal epithelium enclosed by a thin fibrous capsule MANAGEMENT - Conservative excision PROGNOSIS/RECURRENCE - Do not recur  #### Histopathology - Loose or myxoid fibrous tissue with variable numbers of fusiform and stellate fibroblasts, with areas of cellular odontogenic mesenchyme - Periphery is covered by a single layer of columnar or cuboidal epithelium enclosed by a thin fibrous capsule #### Management - Conservative excision #### Prognosis/Recurrence - Do not recur Histopathology micrograph showing a peripheral layer of columnar epithelium overlying loose, myxoid fibrous connective tissue with scattered stellate and fusiform cells. 2.4 DENTINOGENIC GHOST CELL TUMOUR | Definition | A benign but locally infiltrative odontogenic tumour characterized by ameloblastoma-like sheets and islands of epithelium with prominent ghost cell keratinization and varying amounts of dentinoid in the stroma. Both the ghost cells and dentinoid may mineralise. | | :--- | :--- | | **Prevalence** | Rare (0.3-0.5% of all odontogenic tumours) | | **Age** | Most diagnosed between 3^rd and 5^th decades<br>Mean age = 40-47 years<br>Range (1-84 years) | | **Gender** | M>F (2:1), particularly Asian males | | **Aetiology** | Unknown | | **Clinical features** | Slow growing tumour with cortical expansion and occasional cortical perforation +/- mild pain and facial deformity |  #### Definition A benign but locally infiltrative odontogenic tumour characterized by ameloblastoma-like sheets and islands of epithelium with prominent ghost cell keratinization and varying amounts of dentinoid in the stroma. Both the ghost cells and dentinoid may mineralise. #### Prevalence - Rare (0.3–0.5% of all odontogenic tumours) #### Age - Most diagnosed between 3rd and 5th decades - Mean age = 40–47 years - Range: 1–84 years #### Gender - M > F (2:1), particularly Asian males #### Aetiology - Unknown #### Clinical Features - Slow growing tumour with cortical expansion and occasional cortical perforation, +/- mild pain and facial deformity A two-column table listing key characteristics of the dentinogenic ghost cell tumour, with rows for Definition, Prevalence, Age, Gender, Aetiology, and Clinical features. 2.4 DENTINOCENIC GHOST CELL TUMOUR | | | | :--- | :--- | | **Location** | Mand=Max<br>Post > Ant<br>25% are extraosseous (gingiva or alveolar ridge mucosa) | | **Periphery/Shape** | Well-defined (67%) > ill-defined (33%)<br>Unilocular (75%) > Multilocular (25%) | | **Internal Features** | Mixed RL/RO | | **Surrounding Features** | Tooth displacement & resorption common in larger lesions<br>Have been reported in association with odontomas | WHO, 2022   #### Location - Mandible = Maxilla - Posterior > Anterior - 25% are extraosseous (gingiva or alveolar ridge mucosa) #### Periphery / Shape - Well-defined (67%) > ill-defined (33%) - Unilocular (75%) > multilocular (25%) #### Internal Features - Mixed RL/RO #### Surrounding Features - Tooth displacement and resorption common in larger lesions - Have been reported in association with odontomas *WHO, 2022* A two-column table summarizing the radiographic and clinical features of dentinogenic ghost cell tumour. The rows categorize information into Location, Periphery/Shape, Internal Features, and Surrounding Features, providing details such as mandibular vs. maxillary occurrence, unilocular vs. multilocular presentation, mixed radiolucent/radiopaque nature, and associations with tooth displacement or odontomas. A panoramic dental radiograph (orthopantomogram) showing the maxilla and mandible with multiple teeth, some appearing to have root canal fillings. A mixed radiolucent-radiopaque lesion is visible in the anterior mandibular region. # 2.4 DENTINOCENIC GHOST CELL TUMOUR ## HISTOPATHOLOGY - Nests, islands, and sheets of odontogenic epithelium resembling conventional ameloblastoma, with cuboidal to columnar hyperchromatic basal cells that have reverse nuclear polarity - +/- cystic degeneration - Characteristic ghost cells which may undergo mineralisation ## MANAGEMENT/PROGNOSIS/RECURRENCE - 73% recurrence with conservative surgery - 33% recurrence with radical surgery - Long term follow-up recommended - Recurrence has been reported 1-20 years after treatment  #### Histopathology - Nests, islands, and sheets of odontogenic epithelium resembling conventional ameloblastoma, with cuboidal to columnar hyperchromatic basal cells that have reverse nuclear polarity - +/- cystic degeneration - Characteristic ghost cells which may undergo mineralisation #### Management / Prognosis / Recurrence - 73% recurrence with conservative surgery - 33% recurrence with radical surgery - Long term follow-up recommended - Recurrence has been reported 1–20 years after treatment - ==Radical surgery may include marginal or segmental resection.== Histopathology slide showing a dentinogenic ghost cell tumour. The image displays islands of odontogenic epithelium with characteristic pale, eosinophilic 'ghost cells' (anucleate keratinized cells) undergoing mineralization into dysplastic dentin. PART 3: BENIGN MESENCHYMAL ODONTOGENIC TUMOURS 1. Odontogenic myxoma/myxofibroma 2. Odontogenic fibroma 3. Cementoblastoma 4. Cemento-ossifying fibroma 1. Odontogenic myxoma/myxofibroma 2. Odontogenic fibroma 3. Cementoblastoma 4. Cemento-ossifying fibroma 3.1 ODONTOGENIC MYXOMA | | | | :--- | :--- | | **Definition** | A benign neoplasm histologically resembling odontogenic ectomesenchyme and characterized by sparse spindle or stellate cells in a myxoid stroma. | | **Prevalence** | <10% of odontogenic tumours<br>3^rd most frequent after ameloblastoma and odontomas | | **Age** | Wide age range<br>Most commonly young adults (2^nd and 3^rd decades of life) | | **Gender** | F>M (2:1) | | **Aetiology** | Unknown | | **Clinical features** | Slow permeative growth, causing bone destruction, expansion, mobility or absence of tooth, eventual cortical perforation and soft tissue infiltration<br>Firm and not tender to palpation |  #### Definition A benign neoplasm histologically resembling odontogenic ectomesenchyme and characterized by sparse spindle or stellate cells in a myxoid stroma. #### Prevalence - <10% of odontogenic tumours - 3rd most frequent after ameloblastoma and odontomas #### Age - Wide age range - Most commonly young adults (2nd and 3rd decades of life) #### Gender F > M (2:1) #### Aetiology Unknown #### Clinical Features - Slow permeative growth, causing bone destruction, expansion, mobility or absence of tooth, eventual cortical perforation and soft tissue infiltration - Firm and not tender to palpation A two-column table summarizing key characteristics of Odontogenic Myxoma, with category labels on the left and corresponding details on the right. # 3.1 ODONTOGENIC MYXOMA | | | | :--- | :--- | | **Location** | Md (2/3) >Mx (1/3)<br>Most common in premolar/molar region<br>Rarely in non-tooth bearing areas (ramus & condyle)<br>Mx lesions usually involve premolar/molar alveolar process or zygomatic process – may extend to, expand, & obliterate sinus<br>Extraosseous gingival lesions very rare | | **Periphery/ Shape** | Unilocular or multilocular<br>Well defined & corticated<br>May also be poorly defined (esp. in Mx) | White & Pharoah, 2014    #### Location - Md (2/3) > Mx (1/3) - Most common in premolar/molar region - Rarely in non-tooth bearing areas (ramus & condyle) - Mx lesions usually involve premolar/molar alveolar process or zygomatic process — may extend to, expand, & obliterate sinus - Extraosseous gingival lesions very rare #### Periphery / Shape - Unilocular or multilocular - Well defined & corticated - May also be poorly defined (esp. in Mx) *White & Pharoah, 2014* A two-row informational table with blue header cells on the left listing 'Location' and 'Periphery/Shape', paired with corresponding descriptive text about odontogenic myxoma characteristics. Radiograph of a mandible showing a multilocular radiolucent lesion with well-defined, corticated borders in the premolar/molar region. A white arrow points to the central area of the lesion. Radiograph showing a large, multilocular radiolucent lesion with a 'soap bubble' or 'honeycomb' appearance in the posterior mandible. The lesion involves the premolar/molar region and appears to have caused expansion of the cortical plates. # 3.1 ODONTOGENIC MYXOMA | Internal Features | • RL (unilocular cyst-like when pericoronal)<br>• Most have a mixed RL/RO internal pattern<br>• Variable septa appearance - may be curved/straight & fine/coarse – **look for straight septa!**<br> • May show fine soap-bubble or honeycomb appearance, occasionally with **fine straight tennis-racket trabeculations** | | :--- | :--- | | Surrounding Features | • Displaces & loosens teeth (root resorption rare)<br>• Often scallops between roots of adjacent teeth<br>• Tendency to grow along bone without the same amount of expansion as other odontogenic tumours<br>• Considerable expansion (& perforation) when large<br>• Mx lesions tend to obliterate the Mx sinuses as an early feature<br>• May present with periosteal reactive bone layer (larger) |    #### Internal Features - RL (unilocular cyst-like when pericoronal) - Most have a mixed RL/RO internal pattern - Variable septa appearance — may be curved/straight & fine/coarse — **look for straight septa!** - May show fine soap-bubble or honeycomb appearance, occasionally with **fine straight tennis-racket trabeculations** #### Surrounding Features - Displaces & loosens teeth (root resorption rare) - Often scallops between roots of adjacent teeth - Tendency to grow along bone without the same amount of expansion as other odontogenic tumours - Considerable expansion (& perforation) when large - Mx lesions tend to obliterate the Mx sinuses as an early feature - May present with periosteal reactive bone layer (larger) - ==At least one or two straight septa are usually present, which helps distinguish odontogenic myxoma from ameloblastoma.== > [!note] Lecturer — Myxoma Histopathology > Histopathological correlation is required when odontogenic fibroma cannot be distinguished radiographically from odontogenic myxoma. A two-row table with blue header cells on the left listing 'Internal Features' and 'Surrounding Features'. The corresponding right-hand cells contain bulleted lists describing radiographic characteristics, such as mixed RL/RO patterns, straight septa, soap-bubble appearances, and effects on surrounding teeth and bone. A coronal computed tomography (CT) scan of the mandible showing a large, expansile radiolucent lesion with internal septations. A black arrow points to the medial border of the lesion within the right mandibular ramus. Radiograph: A cropped dental radiograph showing a lesion with a mixed radiolucent/radiopaque internal pattern and multiple septa, some of which appear straight. An arrow points to one such straight septum within the trabecular network. 3.1 ODONTOGENIC MYXOMA DIFFERENTIAL DIAGNOSIS | | | | :--- | :--- | | **Other multilocular lesions** | e.g. ameloblastoma, CGCG, central haemangioma, ABCs, OKC<br>May need further imaging with MDCT or MRI<br>Look for <u>**thin straight septa with less than expected bone expansion**</u> | | **Osteogenic sarcoma** | May appear similar due to spiculated periosteal reaction<br>Look for an intact outer cortex for OM | | **Odontogenic fibroma** | Occasionally has same radiographic features & cannot be reliably differentiated |  #### Other Multilocular Lesions - e.g. ameloblastoma, CGCG, central haemangioma, ABCs, OKC - May need further imaging with MDCT or MRI - Look for **thin straight septa with less than expected bone expansion** #### Osteogenic Sarcoma - May appear similar due to spiculated periosteal reaction - Look for an intact outer cortex for OM #### Odontogenic Fibroma - Occasionally has same radiographic features & cannot be reliably differentiated A table listing differential diagnoses for odontogenic myxoma, with rows for "Other multilocular lesions", "Osteogenic sarcoma", and "Odontogenic fibroma". Each row provides distinguishing features or imaging considerations to differentiate these conditions from the primary diagnosis. 3.1 ODONTOGENIC MYXOMA HISTOPATHOLOGY * Predominantly loose myxoid stroma with a sparse population of stellate to spindle cells * Small inactive rests of odontogenic epithelium are present in a small minority and are few in number * Unencapsulated with permeative spread in medullary bone * Appears histologically similar to the dental follicle or developing dental papilla (but clinical and radiologic features are different) MANAGEMENT/PROGNOSIS/RECURRENCE * Lack of capsule and permeative spread account for recurrence rates = 10 to 43% * It is unclear whether recurrence increases with more conservative treatment methods * Maxillary lesions are more likely to recur than mandibular lesions  #### Histopathology - Predominantly loose myxoid stroma with a sparse population of stellate to spindle cells - Small inactive rests of odontogenic epithelium are present in a small minority and are few in number - Unencapsulated with permeative spread in medullary bone - Appears histologically similar to the dental follicle or developing dental papilla (but clinical and radiologic features are different) #### Management / Prognosis / Recurrence - Lack of capsule and permeative spread account for recurrence rates = 10 to 43% - It is unclear whether recurrence increases with more conservative treatment methods - Maxillary lesions are more likely to recur than mandibular lesions Histopathology micrograph showing a loose, myxoid stroma populated by sparse stellate and spindle-shaped cells with long cytoplasmic processes. A trabecula of dense pink bone is visible on the left side, illustrating the permeative nature of the lesion within medullary bone. # 3.2 ODONTOGENIC FIBROMA | | | | :--- | :--- | | **Definition** | A neoplasm of mature fibrous or fibromyxoid connective tissue with variable amounts of inactive-appearing odontogenic epithelium, with or without associated mineralisations | | **Age** | Wide age range; mean = 34 years | | **Gender** | F>M (2.2:1) | | **Aetiology** | Unknown | | **Clinical features** | (Small) asymptomatic<br>(Large) localised swelling, loosening of teeth, pain |  | Feature | Description | | :--- | :--- | | **Definition** | A neoplasm of mature fibrous or fibromyxoid connective tissue with variable amounts of inactive-appearing odontogenic epithelium, with or without associated mineralisations | | **Age** | Wide age range; mean = 34 years | | **Gender** | F>M (2.2:1) | | **Aetiology** | Unknown | | **Clinical features** | (Small) asymptomatic; (Large) localised swelling, loosening of teeth, pain | A two-column table listing clinical characteristics of the condition, with row headers for Definition, Age, Gender, Aetiology, and Clinical features alongside their corresponding descriptions. 3.2 ODONTOGENIC FIBROMA | Location | Max>Mand<br>Maxilla: Anterior to first molar<br>Mandible: Posterior to first molar | | :--- | :--- | | Periphery/ Shape | Well-defined, corticated | | Internal Features | Radiolucent (90%) > RL/RO (10%)<br>Unilocular (small); Multilocular (large) | | Surrounding Features | Divergence or resorption of associated tooth roots | WHO, 2022   | Feature | Description | | :--- | :--- | | **Location** | Max>Mand; Maxilla: anterior to first molar; Mandible: posterior to first molar | | **Periphery/Shape** | Well-defined, corticated | | **Internal Features** | Radiolucent (90%) > RL/RO (10%); unilocular (small); multilocular (large) | | **Surrounding Features** | Divergence or resorption of associated tooth roots | *WHO, 2022* A table summarizing the radiographic and clinical features of Odontogenic Fibroma, with rows for Location, Periphery/Shape, Internal Features, and Surrounding Features. The text details that it is more common in the maxilla (anterior to first molar) than the mandible (posterior to first molar), appears as a well-defined corticated lesion, is predominantly radiolucent and unilocular when small, and causes divergence or resorption of associated tooth roots. Radiograph: A panoramic dental X-ray showing the maxilla and mandible with a prominent, well-defined radiolucent lesion in the posterior mandible. The lesion appears multilocular with scalloped borders and is associated with divergence of the roots of adjacent teeth. 3.2 ODONTOGENIC FIBROMA HISTOPATHOLOGY * Moderately cellular bland fibrous tissue with moderate to dense collagen content, accompanied by varying amounts of dispersed inactive-appearing odontogenic epithelial nests and cords * +/- minor hard tissue formation MANAGEMENT/PROGNOSIS/RECURRENCE * Almost never recur after enucleation and curettage  #### Histopathology - Moderately cellular bland fibrous tissue with moderate to dense collagen content, accompanied by varying amounts of dispersed inactive-appearing odontogenic epithelial nests and cords - +/- minor hard tissue formation #### Management/Prognosis/Recurrence - Almost never recur after enucleation and curettage Histopathology micrograph showing a moderately cellular fibrous connective tissue stroma containing numerous dispersed, inactive-appearing nests and cords of odontogenic epithelium. # 3.3 CEMENTOBLASTOMA | | | | :--- | :--- | | **Definition** | A benign odontogenic neoplasm that forms a rounded mass of cementum on the root of a tooth. | | **Terminology** | Acceptable: benign cementoblastoma<br>Not recommended: true cementoma; cementoma | | **Prevalence** | Relatively rare, 3% of all odontogenic tumours | | **Age** | Wide age range; highest frequency in 2^nd – 3^rd decades | | **Gender** | M=F | | **Aetiology** | Unknown | | **Clinical features** | Slow-growing characteristically painful expansion of the jaw<br>Associated tooth is vital in about 80% of cases |  #### Definition A benign odontogenic neoplasm that forms a rounded mass of cementum on the root of a tooth. #### Terminology - Acceptable: benign cementoblastoma - Not recommended: true cementoma; cementoma #### Prevalence Relatively rare, 3% of all odontogenic tumours. #### Age Wide age range; highest frequency in 2nd – 3rd decades. #### Gender M = F #### Aetiology Unknown. #### Clinical Features - Slow-growing characteristically painful expansion of the jaw - Associated tooth is vital in about 80% of cases A two-column table summarizing the key characteristics of Cementoblastoma, including Definition, Terminology, Prevalence, Age, Gender, Aetiology, and Clinical features. 3.3 CEMENTOBLASTOMA | Location | Develops on the apical third of a tooth root<br>Most common in the posterior mandible<br>Permanent first molar > mandibular premolar and maxillary molar regions > other teeth<br>Involvement of deciduous teeth is rare | | :--- | :--- | | Periphery/ Shape | Well-defined<br>Characteristic radiolucent rim which is continuous with the PDL | | Internal Features | • Mixed RO/RL; majority RO<br>• Amorphous or wheel spoke pattern<br>• Density of the cemental mass usually obscures outline of enveloped root<br>• Maturation of lesion from centre to periphery (as evidenced by lucent band) | | Surrounding Features | External resorption of involved root (2/3$^{rd}$ of cases)<br>Cortical bone perforation & tooth displacement are rare | WHO, 2022    #### Location - Develops on the apical third of a tooth root - Most common in the posterior mandible - Permanent first molar > mandibular premolar and maxillary molar regions > other teeth - Involvement of deciduous teeth is rare #### Periphery / Shape - Well-defined - Characteristic radiolucent rim which is continuous with the PDL #### Internal Features - Mixed RO/RL; majority RO - Amorphous or wheel spoke pattern - Density of the cemental mass usually obscures outline of enveloped root - Maturation of lesion from centre to periphery (as evidenced by lucent band) #### Surrounding Features - External resorption of involved root (2/3rd of cases) - Cortical bone perforation & tooth displacement are rare *WHO, 2022* A four-row table with a blue left-hand header column and alternating light-blue data rows. The headers are 'Location', 'Periphery/Shape', 'Internal Features', and 'Surrounding Features', each followed by bulleted or plain-text descriptions of radiographic and clinical characteristics. Radiograph: A dental X-ray showing the posterior mandible with a radiopaque mass attached to the apex of a tooth root, surrounded by a radiolucent rim continuous with the periodontal ligament space. The lesion exhibits a mixed density with a central radiopaque area and an amorphous or wheel-spoke pattern. A dental radiograph showing the posterior mandible with a large, mixed radiopaque/radiolucent mass enveloping the root apex of a tooth. The lesion appears as an amorphous, cementum-like density that obscures the underlying root outline, consistent with the features of a cemento-oblasteroma. # 3.3 CEMENTOBLASTOMA ## HISTOPATHOLOGY * A mass of dense cellular cementum resembling bone, often with prominent reversal lines, fused with the resorbed surface of the tooth root. * At the periphery there are radiating finger-like trabeculae of newly formed matrix, often associated with plump cementoblasts and cementoclasts and vascular immature fibrous tissue. ## MANAGEMENT/PROGNOSIS/RECURRENCE * Does not usually recur after extraction of the associated tooth and curettage WHO, 2022  #### Histopathology - A mass of dense cellular cementum resembling bone, often with prominent reversal lines, fused with the resorbed surface of the tooth root. - At the periphery there are radiating finger-like trabeculae of newly formed matrix, often associated with plump cementoblasts and cementoclasts and vascular immature fibrous tissue. #### Management / Prognosis / Recurrence - Does not usually recur after extraction of the associated tooth and curettage *WHO, 2022* - ==The periphery is least mature because growth continues there.== - ==Recurrence usually results from incomplete removal or attempted conservation of the tooth.== A histopathological micrograph (H&E stain) showing a mass of dense, pink-staining cellular cementum fused with the resorbed surface of a tooth root. The image illustrates the characteristic radiating trabeculae of newly formed matrix at the periphery. 3.4 CEMENTO-OSSIFYING FIBROMA | Definition | A benign odontogenic fibro-osseous neoplasm arising in the jaws and characterised by production of bone and cementum-like calcifications in a fibrous stroma | | :--- | :--- | | Terminology | Acceptable: Ossifying fibroma, conventional type<br>Not recommended: Cementifying fibroma; ossifying fibroma; ossifying-odontogenic fibroma; periodontoma | | Age | Wide age range; peak 3rd to 4th decade | | Gender | F>M (5:1); primarily Caucasians, followed by African descent | | Aetiology | Odontogenic in origin, related to inactivating mutations in the tumour suppressor gene | | Clinical features | Painless jaw expansion<br>Slow-growing, but can reach considerable size if left untreated<br>Usually solitary, but rare cases of multiple lesions (sporadic or as a component of hyperparathyroidism-jaw tumour syndrome) |  #### Definition A benign odontogenic fibro-osseous neoplasm arising in the jaws and characterised by production of bone and cementum-like calcifications in a fibrous stroma. #### Terminology - **Acceptable:** Ossifying fibroma, conventional type - **Not recommended:** Cementifying fibroma; ossifying fibroma; ossifying-odontogenic fibroma; periodontoma #### Age Wide age range; peak in the 3rd to 4th decade. #### Gender F > M (5:1); primarily Caucasians, followed by African descent. #### Aetiology Odontogenic in origin, related to inactivating mutations in the tumour suppressor gene. #### Clinical Features - Painless jaw expansion - Slow-growing, but can reach considerable size if left untreated - Usually solitary, but rare cases of multiple lesions (sporadic or as a component of hyperparathyroidism-jaw tumour syndrome) - ==Hyperparathyroidism-jaw tumour syndrome is a rare autosomal dominant disorder characterised by parathyroid adenomas or carcinomas, bilateral kidney cysts, hamartomas or Wilms tumours.== A two-column table presenting key characteristics of Cemento-Ossifying Fibroma. The left column lists categories including Definition, Terminology, Age, Gender, Aetiology, and Clinical features, while the right column provides the corresponding descriptive details for each. # 3.4 CEMENTO-OSSIFYING FIBROMA | | | | :--- | :--- | | **Location** | Mand>Max (particularly premolar-molar region) | | **Periphery/ Shape** | Well-defined, corticated<br>Characteristic radiolucent rim | | **Internal Features** | Radiolucent (early stages)<br>Variable internal patterns | | **Surrounding Features** | Cortical thinning and expansion<br>Tooth displacement & root resorption<br>Displacement of antral floor | FIGURE 22-52 Various bone patterns seen in ossifying fibroma. A, Wispy trabecular pattern (arrow). B, Most of this pattern is radiolucent with a few wispy trabeculae (arrow). C, Fibrous dysplasia granular-like pattern (arrows). D, Flocculent pattern with larger tufts of bone formation (arrow). E, Solid, radiopaque, cementum-like pattern (arrow). White & Pharoah, 2014      #### Location Mandible > Maxilla (particularly premolar-molar region). #### Periphery / Shape - Well-defined, corticated - Characteristic radiolucent rim #### Internal Features - Radiolucent (early stages) - Variable internal patterns #### Surrounding Features - Cortical thinning and expansion - Tooth displacement & root resorption - Displacement of antral floor #### Figure 22-52: Various Bone Patterns Seen in Ossifying Fibroma - **A:** Wispy trabecular pattern (arrow) - **B:** Most of this pattern is radiolucent with a few wispy trabeculae (arrow) - **C:** Fibrous dysplasia granular-like pattern (arrows) - **D:** Flocculent pattern with larger tufts of bone formation (arrow) - **E:** Solid, radiopaque, cementum-like pattern (arrow) *White & Pharoah, 2014* A periapical radiograph showing the mandibular premolar-molar region with teeth restored by radiopaque amalgam fillings. An arrow points to a well-defined, corticated lesion located between the tooth roots, which exhibits a characteristic wispy trabecular internal pattern. Radiograph: Two periapical radiographs (labeled B and C) showing various bone patterns seen in ossifying fibroma. Panel B displays a mostly radiolucent area with wispy trabeculae indicated by an arrow, while Panel C shows a granular-like pattern with arrows pointing to the affected region near the maxillary sinus floor. A four-row summary table detailing the radiographic features of cemento-ossifying fibroma, with categories for Location, Periphery/Shape, Internal Features, and Surrounding Features. Radiograph: An occlusal radiograph showing a lesion in the anterior palate/maxillary region. The image illustrates a flocculent pattern with larger tufts of bone formation, as indicated by the arrow. Radiograph showing a solid, radiopaque, cementum-like pattern indicated by an arrow. # 3.4 CEMENTO-OSSIFYING FIBROMA ## HISTOPATHOLOGY * Variable proportions of fibrous and mineralised tissue, more heavily mineralised centrally and with a thin fibrous capsule or well demarcated margin from surrounding normal bone * A fibro-osseous appearance of condensation of woven bone from stroma must be present at least focally * Osteoblastic rimming is frequent and there is bone remodelling in the lesion with infrequent osteoclasts ## MANAGEMENT/PROGNOSIS/RECURRENCE * Rarely recurs with enucleation and curettage WHO, 2022   #### Histopathology - Variable proportions of fibrous and mineralised tissue, more heavily mineralised centrally and with a thin fibrous capsule or well demarcated margin from surrounding normal bone - A fibro-osseous appearance of condensation of woven bone from stroma must be present at least focally - Osteoblastic rimming is frequent and there is bone remodelling in the lesion with infrequent osteoclasts #### Management / Prognosis / Recurrence - Rarely recurs with enucleation and curettage *WHO, 2022* Histopathology slide: A low-power microscopic view of a tissue section stained with hematoxylin and eosin (H&E), showing a well-circumscribed, rounded lesion. The mass is predominantly pink (eosinophilic) indicating mineralized tissue or dense collagen, surrounded by a distinct thin rim of cellular fibrous tissue at the periphery. A photomicrograph of histopathological tissue stained with hematoxylin and eosin (H&E). The image displays irregular trabeculae of pink-staining mineralized bone tissue separated by a cellular fibrous stroma containing spindle-shaped cells. # REFERENCES 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. *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: Ameloblastoma with coarse curved septa ### Question **Scenario:** Radiograph of an ameloblastoma. **What's shown:** Coarse curved septa within the lesion. **Consider:** What do these septa represent and what tumor are they characteristic of? ### Answer **Observations:** - Coarse curved septa are visible within the lesion. **Reasoning:** These septa represent residual bone trapped inside the tumor that has been remodeled into a curved shape by internal cystic structures. This appearance is highly characteristic of ameloblastomas. **Takeaway:** Coarse curved septa in a multilocular radiolucency are a hallmark radiographic feature of ameloblastoma, representing remodeled residual bone. ## Case: Ameloblastoma causing root resorption ### Question **Scenario:** Radiograph demonstrating the effects of an ameloblastoma on adjacent teeth. **What's shown:** Blunted appearance of tooth roots. **Consider:** How does the root resorption caused by this benign tumor compare to that caused by cysts? ### Answer **Observations:** - Tooth roots exhibit a blunted appearance due to resorption. **Reasoning:** While both cysts and benign tumors can cause root resorption, benign tumors like ameloblastomas are much more likely to cause significant root resorption compared to cysts. **Takeaway:** Benign odontogenic tumors are more likely to cause pronounced root resorption (blunting) than cystic lesions. ## Case: Maxillary versus mandibular ameloblastoma borders ### Question **Scenario:** Radiographs comparing an ameloblastoma in the maxilla with those in the mandible. **What's shown:** Ill-defined borders in the maxillary lesion compared to well-defined borders in the mandibular lesions. **Consider:** How does the anatomical location affect the radiographic visibility of the tumor's borders? ### Answer **Observations:** - The maxillary ameloblastoma has ill-defined borders. - The mandibular ameloblastomas have well-defined, corticated borders. **Reasoning:** Maxillary lesions are generally more ill-defined and harder to see the borders of compared to mandibular lesions, likely due to the anatomical structures and bone density differences in the maxilla. **Takeaway:** Ameloblastomas in the maxilla tend to have ill-defined borders, making them harder to delineate radiographically than those in the mandible. ## Case: Anterior versus posterior ameloblastoma locule size ### Question **Scenario:** Radiographs of ameloblastomas located in the anterior and posterior regions of the jaw. **What's shown:** Smaller locules in the anterior lesion and larger locules in the posterior lesion. **Consider:** How does the size of the locules vary depending on the location of the ameloblastoma? ### Answer **Observations:** - The anterior lesion exhibits smaller locules. - The posterior lesion exhibits larger locules. **Reasoning:** The internal multilocular appearance, specifically the size of the locules, tends to vary by location, with anterior lesions typically having smaller locules and posterior lesions having larger ones. **Takeaway:** Locule size in ameloblastomas varies by location, being smaller in anterior lesions and larger in posterior lesions. ## Case: Ameloblastoma with cortical perforation and tooth displacement ### Question **Scenario:** Radiograph of an ameloblastoma demonstrating mass effect. **What's shown:** Missing white cortical plate, blunted roots, and teeth angled in different directions. **Consider:** What are the space-occupying effects demonstrated by this lesion on the surrounding structures? ### Answer **Observations:** - Perforation of the cortex (the white cortical plate is no longer visible). - Root resorption with blunting of the roots. - Tooth displacement with teeth angled in different directions. **Reasoning:** As a space-occupying lesion, the ameloblastoma exerts pressure, leading to cortical expansion and eventual perforation when periosteal new bone cannot keep up. It also displaces teeth and causes root resorption. **Takeaway:** Ameloblastomas demonstrate classic mass effect features, including cortical perforation, root resorption, and significant tooth displacement. ## Case: Ameloblastoma with coarse curved septa ### Question **Scenario:** Radiograph of an ameloblastoma. **What's shown:** Coarse curved septa within the lesion. **Consider:** What do these septa represent and what tumor are they characteristic of?   ### Answer **Observations:** - Coarse curved septa are visible within the lesion. **Reasoning:** These septa represent residual bone trapped inside the tumor that has been remodeled into a curved shape by internal cystic structures. This appearance is highly characteristic of ameloblastomas. **Takeaway:** Coarse curved septa in a multilocular radiolucency are a hallmark radiographic feature of ameloblastoma, representing remodeled residual bone. ## Case: Ameloblastoma causing root resorption ### Question **Scenario:** Radiograph demonstrating the effects of an ameloblastoma on adjacent teeth. **What's shown:** Blunted appearance of tooth roots. **Consider:** How does the root resorption caused by this benign tumor compare to that caused by cysts?  ### Answer **Observations:** - Tooth roots exhibit a blunted appearance due to resorption. **Reasoning:** While both cysts and benign tumors can cause root resorption, benign tumors like ameloblastomas are much more likely to cause significant root resorption compared to cysts. **Takeaway:** Benign odontogenic tumors are more likely to cause pronounced root resorption (blunting) than cystic lesions. ## Case: Maxillary versus mandibular ameloblastoma borders ### Question **Scenario:** Radiographs comparing an ameloblastoma in the maxilla with those in the mandible. **What's shown:** Ill-defined borders in the maxillary lesion compared to well-defined borders in the mandibular lesions. **Consider:** How does the anatomical location affect the radiographic visibility of the tumor's borders?   ### Answer **Observations:** - The maxillary ameloblastoma has ill-defined borders. - The mandibular ameloblastomas have well-defined, corticated borders. **Reasoning:** Maxillary lesions are generally more ill-defined and harder to see the borders of compared to mandibular lesions, likely due to the anatomical structures and bone density differences in the maxilla. **Takeaway:** Ameloblastomas in the maxilla tend to have ill-defined borders, making them harder to delineate radiographically than those in the mandible. ## Case: Anterior versus posterior ameloblastoma locule size ### Question **Scenario:** Radiographs of ameloblastomas located in the anterior and posterior regions of the jaw. **What's shown:** Smaller locules in the anterior lesion and larger locules in the posterior lesion. **Consider:** How does the size of the locules vary depending on the location of the ameloblastoma?    ### Answer **Observations:** - The anterior lesion exhibits smaller locules. - The posterior lesion exhibits larger locules. **Reasoning:** The internal multilocular appearance, specifically the size of the locules, tends to vary by location, with anterior lesions typically having smaller locules and posterior lesions having larger ones. **Takeaway:** Locule size in ameloblastomas varies by location, being smaller in anterior lesions and larger in posterior lesions. ## Case: Ameloblastoma with cortical perforation and tooth displacement ### Question **Scenario:** Radiograph of an ameloblastoma demonstrating mass effect. **What's shown:** Missing white cortical plate, blunted roots, and teeth angled in different directions. **Consider:** What are the space-occupying effects demonstrated by this lesion on the surrounding structures?  ### Answer **Observations:** - Perforation of the cortex (the white cortical plate is no longer visible). - Root resorption with blunting of the roots. - Tooth displacement with teeth angled in different directions. **Reasoning:** As a space-occupying lesion, the ameloblastoma exerts pressure, leading to cortical expansion and eventual perforation when periosteal new bone cannot keep up. It also displaces teeth and causes root resorption. **Takeaway:** Ameloblastomas demonstrate classic mass effect features, including cortical perforation, root resorption, and significant tooth displacement. Case: Ameloblastoma with coarse curved septa A dental radiograph (likely a periapical or panoramic view) showing the mandible with teeth, including one with a metallic restoration. A white arrow points to an expansile lesion in the jawbone characterized by a multilocular radiolucent appearance with internal septa, illustrating the 'internal structure' and 'expansion of jaw cortices' features discussed in the text. A periapical dental radiograph showing the posterior mandible with multiple teeth exhibiting large, bright white restorations (radiopaque). The image illustrates general imaging features such as the internal structure of bone and potential effects on surrounding structures like tooth displacement or resorption. A dental radiograph (likely a periapical or panoramic view) showing the mandible with teeth, including one with a metallic restoration. A white arrow points to an expansile lesion in the jawbone characterized by a multilocular radiolucent appearance with internal septa, illustrating the 'internal structure' and 'expansion of jaw cortices' features discussed in the text. A dental radiograph showing the posterior mandible with a large, well-defined multilocular radiolucent lesion containing curved corticated borders and displacing associated teeth. The image displays two radiographic views of a jaw, likely an orthopantomogram and a lateral or oblique view. Both show extensive multilocular radiolucencies with well-defined borders, creating a characteristic "soap bubble" or "honeycomb" appearance within the bone. A composite medical image featuring an axial CT scan (top, labeled 'A') and a panoramic dental radiograph (bottom). The images illustrate the internal features of a lesion in the mandible, specifically showing a multilocular radiolucency with coarse septae ('soap-bubble' appearance) and associated root resorption and tooth displacement. Radiograph: A dental radiograph showing a lesion with mixed radiolucent and radiopaque features, indicated by black arrows, alongside unilocular radiolucencies marked by white arrows. Radiograph: A panoramic dental X-ray showing the mandible with a large, multilocular radiolucent lesion in the anterior region. The lesion exhibits a coarse, curved septae pattern creating a "soap-bubble" or honeycomb appearance, consistent with the internal features of a conventional ameloblastoma. A composite medical image featuring an axial CT scan (top, labeled 'A') and a panoramic dental radiograph (bottom). The images illustrate the internal features of a lesion in the mandible, specifically showing a multilocular radiolucency with coarse septae ('soap-bubble' appearance) and associated root resorption and tooth displacement. ## Case: Unicystic ameloblastoma mimicking a radicular cyst ### Question **Scenario:** Radiograph of a lesion that clinically and radiographically resembled a radicular cyst, leading to endodontic treatment. **What's shown:** A unilocular radiolucency resembling a radicular cyst. **Consider:** What was the actual histopathological diagnosis despite the initial clinical appearance and treatment? ### Answer **Observations:** - The lesion appears radiographically identical to a radicular cyst. - Endodontic treatment was initially carried out. **Reasoning:** Unicystic ameloblastomas can occur in periapical locations and mimic radicular cysts both clinically and radiographically. Definitive diagnosis requires histopathological correlation, which in this case confirmed a unicystic ameloblastoma. **Takeaway:** Unicystic ameloblastomas can mimic radicular cysts radiographically, necessitating histopathological examination for a definitive diagnosis. ## Case: Unicystic ameloblastoma with pseudo-septa ### Question **Scenario:** Radiograph of a unicystic ameloblastoma. **What's shown:** Apparent septa within a unilocular lesion. **Consider:** Are these true septa, and what do they actually represent? ### Answer **Observations:** - The unilocular lesion appears to have internal septa. **Reasoning:** Although it may look like there are true septa as seen in conventional multilocular ameloblastomas, these are not true septa. They are simply areas of residual bone within the unilocular cyst cavity. **Takeaway:** Apparent septa in a unicystic ameloblastoma are not true septa but rather areas of residual bone. ## Case: Adenomatoid odontogenic tumor surrounding a tooth ### Question **Scenario:** Radiograph of an adenomatoid odontogenic tumor (AOT) associated with an unerupted tooth. **What's shown:** A radiolucency surrounding the greater part of the tooth, including the root and part of the crown. **Consider:** How does the attachment of this lesion to the tooth differ from a dentigerous cyst? ### Answer **Observations:** - The lesion surrounds almost the entire root and part of the crown. - It does not attach at the cementoenamel junction (CEJ). **Reasoning:** Unlike a dentigerous cyst which typically attaches at the CEJ, an AOT tends to surround the greater part of the tooth, extending apically past the CEJ to encompass the root. **Takeaway:** An AOT often surrounds the entire root and part of the crown without attaching at the CEJ, distinguishing it from a dentigerous cyst. ## Case: Adenomatoid odontogenic tumor with corticated border and tooth displacement ### Question **Scenario:** Radiographs of adenomatoid odontogenic tumors. **What's shown:** Well-defined unilocular radiolucencies with a thin white corticated border and associated tooth displacement. **Consider:** What are the characteristic border features and effects on surrounding structures for this tumor? ### Answer **Observations:** - A thin white corticated or sclerotic border is present. - The tumor causes displacement of the adjacent tooth. **Reasoning:** AOTs typically present as well-defined, unilocular radiolucencies with a distinct corticated border. While they cause tooth displacement, root resorption is quite rare. **Takeaway:** AOTs characteristically display a well-defined corticated border and cause tooth displacement, but rarely cause root resorption. ## Case: Squamous odontogenic tumor on a 2D image ### Question **Scenario:** 2D radiograph of a squamous odontogenic tumor. **What's shown:** A triangular or semicircular unilocular radiolucency along tooth roots. **Consider:** Why can't cortical bone expansion and perforation be appreciated on this specific image? ## Case: Unicystic ameloblastoma mimicking a radicular cyst ### Question **Scenario:** Radiograph of a lesion that clinically and radiographically resembled a radicular cyst, leading to endodontic treatment. **What's shown:** A unilocular radiolucency resembling a radicular cyst. **Consider:** What was the actual histopathological diagnosis despite the initial clinical appearance and treatment?   ### Answer **Observations:** - The lesion appears radiographically identical to a radicular cyst. - Endodontic treatment was initially carried out. **Reasoning:** Unicystic ameloblastomas can occur in periapical locations and mimic radicular cysts both clinically and radiographically. Definitive diagnosis requires histopathological correlation, which in this case confirmed a unicystic ameloblastoma. **Takeaway:** Unicystic ameloblastomas can mimic radicular cysts radiographically, necessitating histopathological examination for a definitive diagnosis. ## Case: Unicystic ameloblastoma with pseudo-septa ### Question **Scenario:** Radiograph of a unicystic ameloblastoma. **What's shown:** Apparent septa within a unilocular lesion. **Consider:** Are these true septa, and what do they actually represent?   ### Answer **Observations:** - The unilocular lesion appears to have internal septa. **Reasoning:** Although it may look like there are true septa as seen in conventional multilocular ameloblastomas, these are not true septa. They are simply areas of residual bone within the unilocular cyst cavity. **Takeaway:** Apparent septa in a unicystic ameloblastoma are not true septa but rather areas of residual bone. ## Case: Adenomatoid odontogenic tumor surrounding a tooth ### Question **Scenario:** Radiograph of an adenomatoid odontogenic tumor (AOT) associated with an unerupted tooth. **What's shown:** A radiolucency surrounding the greater part of the tooth, including the root and part of the crown. **Consider:** How does the attachment of this lesion to the tooth differ from a dentigerous cyst?    ### Answer **Observations:** - The lesion surrounds almost the entire root and part of the crown. - It does not attach at the cementoenamel junction (CEJ). **Reasoning:** Unlike a dentigerous cyst which typically attaches at the CEJ, an AOT tends to surround the greater part of the tooth, extending apically past the CEJ to encompass the root. **Takeaway:** An AOT often surrounds the entire root and part of the crown without attaching at the CEJ, distinguishing it from a dentigerous cyst. ## Case: Adenomatoid odontogenic tumor with corticated border and tooth displacement ### Question **Scenario:** Radiographs of adenomatoid odontogenic tumors. **What's shown:** Well-defined unilocular radiolucencies with a thin white corticated border and associated tooth displacement. **Consider:** What are the characteristic border features and effects on surrounding structures for this tumor?   ### Answer **Observations:** - A thin white corticated or sclerotic border is present. - The tumor causes displacement of the adjacent tooth. **Reasoning:** AOTs typically present as well-defined, unilocular radiolucencies with a distinct corticated border. While they cause tooth displacement, root resorption is quite rare. **Takeaway:** AOTs characteristically display a well-defined corticated border and cause tooth displacement, but rarely cause root resorption. ## Case: Squamous odontogenic tumor on a 2D image ### Question **Scenario:** 2D radiograph of a squamous odontogenic tumor. **What's shown:** A triangular or semicircular unilocular radiolucency along tooth roots. **Consider:** Why can't cortical bone expansion and perforation be appreciated on this specific image?  Case: Unicystic ameloblastoma mimicking a radicular cyst Radiograph: A dental X-ray showing the posterior mandible with a well-defined, corticated radiolucent lesion located in the area of the third molar and ascending ramus. The lesion appears to be associated with an impacted tooth, consistent with the presentation of a unicystic ameloblastoma. Radiograph: A dental X-ray showing the mandibular teeth, including posterior molars and premolars with visible root structures. Several teeth in the lower jaw exhibit bright white linear densities within their roots, consistent with endodontic filling material (root canal treatment). The image illustrates the appearance of treated teeth and surrounding bone structure. A dental radiograph showing a large, unilocular radiolucency in the posterior mandible associated with an impacted tooth. The lesion surrounds the crown of the unerupted third molar and extends superiorly towards the maxilla. A panoramic radiograph showing the posterior mandible with a large, well-defined unilocular radiolucency surrounding the crown of an impacted tooth. The lesion displaces the unerupted tooth inferiorly and appears to cause root resorption on the adjacent erupted molar. A A radiograph of the maxilla showing a well-defined, unilocular radiolucency surrounding the crown of an unerupted permanent tooth. The lesion contains multiple small, irregular radiopaque foci resembling calcifications or 'pebbles', and white arrows indicate the periphery of the mass. C Radiograph: A dental X-ray of the maxilla showing a large, well-defined radiolucent lesion associated with an impacted tooth. The lesion contains scattered radiopaque calcifications, giving it a mixed density appearance. A periapical radiograph (labeled C) showing the maxillary anterior region with a well-defined radiolucent lesion associated with an impacted tooth. The lesion contains scattered radiopaque foci, appearing as 'snowflake' or pebble-like calcifications within the unilocular area. A cropped cone-beam CT radiograph (labeled 'B') showing a dental lesion associated with the root of a premolar. The image reveals a radiolucent area containing small, distinct radiopaque foci described as pebble-like calcifications. Radiograph: A cropped panoramic dental image showing a large, well-defined radiolucent lesion associated with an unerupted tooth in the mandible. The crop corresponds to panel A of the original figure caption, which notes that there are no apparent internal calcifications visible in this view. WHO, 2017 Radiograph: A dental panoramic X-ray showing the posterior region of the mandible. It depicts a well-defined, radiolucent lesion situated between the roots of the molars and premolars, consistent with the appearance of an odontogenic tumour. ### Answer **Observations:** - A triangular/semicircular unilocular radiolucency is visible along the roots. - Cortical expansion and perforation are not visible. **Reasoning:** The image is a 2D radiograph, which lacks the cross-sectional detail needed to appreciate buccal or lingual cortical bone expansion and perforation. **Takeaway:** 2D radiographs may fail to show cortical expansion and perforation in squamous odontogenic tumors; cross-sectional imaging is often needed to evaluate these features. ## Case: Calcifying epithelial odontogenic tumor preventing tooth eruption ### Question **Scenario:** Radiograph of a mixed density lesion in the jaw. **What's shown:** A mixed radiolucent-radiopaque lesion preventing the eruption of a canine, with cortical expansion not appreciable on the 2D OPG. **Consider:** What is the effect of this lesion on the adjacent tooth and cortex? ### Answer **Observations:** - A mixed density lesion is present. - The canine has not erupted due to the lesion. - Cortical expansion is present but not visible on the 2D OPG. **Reasoning:** Calcifying epithelial odontogenic tumors act as space-occupying lesions that can prevent tooth eruption. While they typically cause cortical expansion, this may not be appreciable on a 2D panoramic radiograph. **Takeaway:** Calcifying epithelial odontogenic tumors can prevent tooth eruption and cause cortical expansion, though expansion may be missed on 2D imaging. ## Case: Compound odontoma in the maxillary anterior region ### Question **Scenario:** Radiograph of a compound odontoma. **What's shown:** Distinct tooth-like structures (denticles) in the maxillary anterior region. **Consider:** What is the typical location and radiographic appearance of this lesion? ### Answer **Observations:** - Multiple distinct tooth-like structures (denticles) are visible. - The lesion is located in the maxillary anterior region. **Reasoning:** Compound odontomas are more common in the maxillary anterior region and radiographically present as multiple distinct, rudimentary tooth-like structures. **Takeaway:** Compound odontomas typically occur in the maxillary anterior region and appear as multiple distinct tooth-like structures (denticles). ## Case: Odontoma with a lucent band and corticated periphery ### Question **Scenario:** Radiograph of an odontoma. **What's shown:** Tooth-like structures surrounded by a lucent band and a corticated periphery. **Consider:** What are the characteristic border features surrounding the calcified structures in this lesion? ### Answer **Observations:** - A lucent band surrounds the tooth-like structures. - A corticated periphery is present. **Reasoning:** Odontomas typically present as well-defined mixed radiopaque structures surrounded by a narrow radiolucent band (representing the follicular capsule) and a corticated border. **Takeaway:** Odontomas are characteristically surrounded by a radiolucent band and a corticated periphery. ## Case: Compound odontoma histology ### Question **Scenario:** Histopathological image of a compound odontoma. **What's shown:** Individual denticles composed of dentine and enamel. **Consider:** What dental hard tissues are visible in this histological specimen? ### Answer **Observations:** - Individual denticles are visible. - The structures contain dentine and enamel. **Reasoning:** Histologically, compound odontomas contain multiple rudimentary teeth exhibiting dentine and enamel matrix, though the dentine may show irregularity of the tubular structure. **Takeaway:** Histologically, compound odontomas consist of multiple rudimentary teeth (denticles) made of dentine and enamel. ## Case: Ameloblastic fibroma with tooth displacement and jaw expansion ### Answer **Observations:** - A triangular/semicircular unilocular radiolucency is visible along the roots. - Cortical expansion and perforation are not visible. **Reasoning:** The image is a 2D radiograph, which lacks the cross-sectional detail needed to appreciate buccal or lingual cortical bone expansion and perforation. **Takeaway:** 2D radiographs may fail to show cortical expansion and perforation in squamous odontogenic tumors; cross-sectional imaging is often needed to evaluate these features. ## Case: Calcifying epithelial odontogenic tumor preventing tooth eruption ### Question **Scenario:** Radiograph of a mixed density lesion in the jaw. **What's shown:** A mixed radiolucent-radiopaque lesion preventing the eruption of a canine, with cortical expansion not appreciable on the 2D OPG. **Consider:** What is the effect of this lesion on the adjacent tooth and cortex?  ### Answer **Observations:** - A mixed density lesion is present. - The canine has not erupted due to the lesion. - Cortical expansion is present but not visible on the 2D OPG. **Reasoning:** Calcifying epithelial odontogenic tumors act as space-occupying lesions that can prevent tooth eruption. While they typically cause cortical expansion, this may not be appreciable on a 2D panoramic radiograph. **Takeaway:** Calcifying epithelial odontogenic tumors can prevent tooth eruption and cause cortical expansion, though expansion may be missed on 2D imaging. ## Case: Compound odontoma in the maxillary anterior region ### Question **Scenario:** Radiograph of a compound odontoma. **What's shown:** Distinct tooth-like structures (denticles) in the maxillary anterior region. **Consider:** What is the typical location and radiographic appearance of this lesion?  ### Answer **Observations:** - Multiple distinct tooth-like structures (denticles) are visible. - The lesion is located in the maxillary anterior region. **Reasoning:** Compound odontomas are more common in the maxillary anterior region and radiographically present as multiple distinct, rudimentary tooth-like structures. **Takeaway:** Compound odontomas typically occur in the maxillary anterior region and appear as multiple distinct tooth-like structures (denticles). ## Case: Odontoma with a lucent band and corticated periphery ### Question **Scenario:** Radiograph of an odontoma. **What's shown:** Tooth-like structures surrounded by a lucent band and a corticated periphery. **Consider:** What are the characteristic border features surrounding the calcified structures in this lesion?   ### Answer **Observations:** - A lucent band surrounds the tooth-like structures. - A corticated periphery is present. **Reasoning:** Odontomas typically present as well-defined mixed radiopaque structures surrounded by a narrow radiolucent band (representing the follicular capsule) and a corticated border. **Takeaway:** Odontomas are characteristically surrounded by a radiolucent band and a corticated periphery. ## Case: Compound odontoma histology ### Question **Scenario:** Histopathological image of a compound odontoma. **What's shown:** Individual denticles composed of dentine and enamel. **Consider:** What dental hard tissues are visible in this histological specimen?   ### Answer **Observations:** - Individual denticles are visible. - The structures contain dentine and enamel. **Reasoning:** Histologically, compound odontomas contain multiple rudimentary teeth exhibiting dentine and enamel matrix, though the dentine may show irregularity of the tubular structure. **Takeaway:** Histologically, compound odontomas consist of multiple rudimentary teeth (denticles) made of dentine and enamel. ## Case: Ameloblastic fibroma with tooth displacement and jaw expansion Case: Squamous odontogenic tumor on a 2D image > Answer Radiograph: A cropped dental radiograph showing the posterior mandible with an impacted third molar. The image illustrates a lesion associated with the crown of the embedded tooth, appearing as mixed radiolucent and radiopaque areas (calcifications) that correspond to the 'driven snow' appearance described in the text. 2.1 ODONTOMA | **Definition** | Mixed odontogenic hamartomas that mature from soft tissue to predominantly dental hard tissues with a small amount of residual odontogenic epithelium and ectomesenchyme A dental radiograph showing the maxillary teeth and surrounding bone structure, with a focus on an area between the roots or superior to the crowns where an odontoma may be present. The image highlights well-defined structures that could represent tooth-like formations (denticles) typical of a compound odontoma. (WHO, 2022) Radiograph: A dental X-ray showing a large, irregular radiopaque mass located posteriorly in the jaw (likely mandible), associated with an unerupted tooth. The lesion appears as a disorganised calcified structure, consistent with the complex odontoma described in the table. A histopathology micrograph showing multiple discrete, rounded masses of eosinophilic tissue (dentin) surrounded by thin basophilic rims (enamel matrix), consistent with the description of a compound odontoma containing rudimentary teeth. A histopathology micrograph showing a disorganized mass of mature tubular dentine (stained pink) intermixed with rounded zones of enamel matrix (clear/white areas), consistent with the description of a complex odontoma. ### Question **Scenario:** Radiographs (including an occlusal view) of an ameloblastic fibroma. **What's shown:** Posterior displacement of the root of tooth 47, and expansion of both buccal and lingual cortices. **Consider:** What are the mass effect features demonstrated in this case? ### Answer **Observations:** - The root of tooth 47 is displaced posteriorly. - There is expansion of both the buccal and lingual cortices. **Reasoning:** Ameloblastic fibromas demonstrate mass effect features such as tooth displacement and jaw expansion. Root resorption is less common, and cortical perforation is rare due to the slow growth allowing periosteal new bone formation. **Takeaway:** Ameloblastic fibromas typically cause tooth displacement and cortical expansion, but rarely cause root resorption or cortical perforation. ## Case: Ameloblastic fibro-odontoma with calcifications ### Question **Scenario:** Radiographs of ameloblastic fibro-odontomas. **What's shown:** Predominantly lucent internal components with areas of calcification, some resembling an outer enamel rim. **Consider:** How do the calcifications in this mixed density lesion present? ### Answer **Observations:** - The internal component is mostly lucent. - There are areas of calcification, some with an outer enamel-like rim. **Reasoning:** Ameloblastic fibro-odontomas are mixed density lesions. When small, they may have only one or two radiopacities, but as they enlarge, the calcified material becomes more extensive, sometimes forming tooth-like structures with an enamel rim. **Takeaway:** Ameloblastic fibro-odontomas present as mixed density lesions with varying amounts of calcification that can become extensive and sometimes resemble tooth-like structures. ## Case: Odontogenic myxoma with spiculated periosteal reaction ### Question **Scenario:** Radiograph of an odontogenic myxoma. **What's shown:** A periosteal reactive bone layer with a spiculated appearance. **Consider:** What is causing this spiculated periosteal reaction? ### Answer **Observations:** - A spiculated periosteal reactive bone layer is visible. **Reasoning:** The spiculated appearance is a result of the reaction of the periosteum to the lesion. While it can mimic malignant tumors like osteogenic sarcoma, the presence of an intact outer cortex indicates a benign process like odontogenic myxoma. **Takeaway:** Odontogenic myxomas can cause a spiculated periosteal reaction, but an intact outer cortex helps differentiate it from malignant bone-forming tumors. ## Case: Odontogenic fibroma with panoramic artifact ### Question **Scenario:** OPG of an odontogenic fibroma. **What's shown:** An anterior border that appears ill-defined. **Consider:** Why does the anterior border appear ill-defined on this specific radiograph? ### Answer **Observations:** - The anterior border of the lesion appears ill-defined. **Reasoning:** The ill-defined appearance is an artifact from the panoramic technique (OPG) rather than a true feature of the lesion, which typically has well-defined corticated margins. **Takeaway:** Panoramic radiograph artifacts can create the illusion of ill-defined borders in lesions that are actually well-corticated. ## Case: Cementoblastoma fused to a tooth root ### Question **Scenario:** Radiograph/histology of a cementoblastoma. **What's shown:** A cemental mass fused to a partially resorbed tooth root. **Consider:** What is the relationship between the radiopaque mass and the tooth root? ### Answer **Observations:** - A radiopaque cemental mass is fused to the tooth root. - The tooth root is partially resorbed. **Reasoning:** Cementoblastomas develop at the apical third of a tooth root and are characteristically fused to it. The density of the cemental mass often obscures the root outline, and root resorption occurs in about two-thirds of cases. **Takeaway:** Cementoblastomas are characteristically fused to the affected tooth root and frequently cause root resorption. ### Question **Scenario:** Radiographs (including an occlusal view) of an ameloblastic fibroma. **What's shown:** Posterior displacement of the root of tooth 47, and expansion of both buccal and lingual cortices. **Consider:** What are the mass effect features demonstrated in this case?    ### Answer **Observations:** - The root of tooth 47 is displaced posteriorly. - There is expansion of both the buccal and lingual cortices. **Reasoning:** Ameloblastic fibromas demonstrate mass effect features such as tooth displacement and jaw expansion. Root resorption is less common, and cortical perforation is rare due to the slow growth allowing periosteal new bone formation. **Takeaway:** Ameloblastic fibromas typically cause tooth displacement and cortical expansion, but rarely cause root resorption or cortical perforation. ## Case: Ameloblastic fibro-odontoma with calcifications ### Question **Scenario:** Radiographs of ameloblastic fibro-odontomas. **What's shown:** Predominantly lucent internal components with areas of calcification, some resembling an outer enamel rim. **Consider:** How do the calcifications in this mixed density lesion present?    ### Answer **Observations:** - The internal component is mostly lucent. - There are areas of calcification, some with an outer enamel-like rim. **Reasoning:** Ameloblastic fibro-odontomas are mixed density lesions. When small, they may have only one or two radiopacities, but as they enlarge, the calcified material becomes more extensive, sometimes forming tooth-like structures with an enamel rim. **Takeaway:** Ameloblastic fibro-odontomas present as mixed density lesions with varying amounts of calcification that can become extensive and sometimes resemble tooth-like structures. ## Case: Odontogenic myxoma with spiculated periosteal reaction ### Question **Scenario:** Radiograph of an odontogenic myxoma. **What's shown:** A periosteal reactive bone layer with a spiculated appearance. **Consider:** What is causing this spiculated periosteal reaction?   ### Answer **Observations:** - A spiculated periosteal reactive bone layer is visible. **Reasoning:** The spiculated appearance is a result of the reaction of the periosteum to the lesion. While it can mimic malignant tumors like osteogenic sarcoma, the presence of an intact outer cortex indicates a benign process like odontogenic myxoma. **Takeaway:** Odontogenic myxomas can cause a spiculated periosteal reaction, but an intact outer cortex helps differentiate it from malignant bone-forming tumors. ## Case: Odontogenic fibroma with panoramic artifact ### Question **Scenario:** OPG of an odontogenic fibroma. **What's shown:** An anterior border that appears ill-defined. **Consider:** Why does the anterior border appear ill-defined on this specific radiograph?  ### Answer **Observations:** - The anterior border of the lesion appears ill-defined. **Reasoning:** The ill-defined appearance is an artifact from the panoramic technique (OPG) rather than a true feature of the lesion, which typically has well-defined corticated margins. **Takeaway:** Panoramic radiograph artifacts can create the illusion of ill-defined borders in lesions that are actually well-corticated. ## Case: Cementoblastoma fused to a tooth root ### Question **Scenario:** Radiograph/histology of a cementoblastoma. **What's shown:** A cemental mass fused to a partially resorbed tooth root. **Consider:** What is the relationship between the radiopaque mass and the tooth root?    ### Answer **Observations:** - A radiopaque cemental mass is fused to the tooth root. - The tooth root is partially resorbed. **Reasoning:** Cementoblastomas develop at the apical third of a tooth root and are characteristically fused to it. The density of the cemental mass often obscures the root outline, and root resorption occurs in about two-thirds of cases. **Takeaway:** Cementoblastomas are characteristically fused to the affected tooth root and frequently cause root resorption. Case: Ameloblastic fibroma with tooth displacement and jaw expansion > Question A panoramic dental radiograph (labeled 'A') showing the posterior mandible with a white arrow pointing to a well-defined, corticated radiolucent lesion associated with an impacted tooth. A Radiograph: A lateral jaw radiograph showing a large, well-defined multilocular radiolucent lesion in the posterior mandible. The lesion contains distinct curved septa and is associated with an impacted tooth displaced inferiorly within the radiolucency. B A dental radiograph showing a large, well-defined multilocular radiolucency in the posterior mandible. The lesion contains multiple rounded radiopaque structures resembling developing tooth crowns and is associated with displaced teeth. H Radiograph: A dental panoramic X-ray showing developing teeth in the jaw, with a white arrow pointing to a small radiopaque structure located between the roots of an erupted tooth and an unerupted tooth bud. Radiograph: A dental X-ray image showing multiple teeth in the posterior jaw, including impacted molars with developing roots. The image illustrates a radiolucent area associated with an impacted tooth that contains discrete radiopaque calcifications, consistent with the features of an ameloblastic fibro-odontoma. C Radiograph: A panoramic dental X-ray showing a large, well-defined radiolucent lesion with internal radiopaque calcifications in the posterior mandible. The lesion surrounds an impacted tooth, illustrating the mixed radiolucent-radiopaque appearance characteristic of an ameloblastic fibro-odontoma. C A coronal computed tomography (CT) scan of the mandible showing a large, expansile radiolucent lesion with internal septations. A black arrow points to the medial border of the lesion within the right mandibular ramus. D Radiograph: A cropped dental radiograph showing a lesion with a mixed radiolucent/radiopaque internal pattern and multiple septa, some of which appear straight. An arrow points to one such straight septum within the trabecular network. Radiograph: A panoramic dental X-ray showing the maxilla and mandible with a prominent, well-defined radiolucent lesion in the posterior mandible. The lesion appears multilocular with scalloped borders and is associated with divergence of the roots of adjacent teeth. (White & Pharoah, 2014) Radiograph: A dental X-ray showing the posterior mandible with a radiopaque mass attached to the apex of a tooth root, surrounded by a radiolucent rim continuous with the periodontal ligament space. The lesion exhibits a mixed density with a central radiopaque area and an amorphous or wheel-spoke pattern. A dental radiograph showing the posterior mandible with a large, mixed radiopaque/radiolucent mass enveloping the root apex of a tooth. The lesion appears as an amorphous, cementum-like density that obscures the underlying root outline, consistent with the features of a cemento-oblasteroma. A histopathological micrograph (H&E stain) showing a mass of dense, pink-staining cellular cementum fused with the resorbed surface of a tooth root. The image illustrates the characteristic radiating trabeculae of newly formed matrix at the periphery. ## Case: Cemento-ossifying fibroma with jaw expansion ### Question **Scenario:** Occlusal radiograph of a cemento-ossifying fibroma. **What's shown:** Significant expansion of the jaw. **Consider:** What effect does this lesion have on the jawbone as seen on this view? ### Answer **Observations:** - Marked expansion of the jaw is visible. **Reasoning:** Cemento-ossifying fibromas typically demonstrate cortical thinning and significant expansion, which is clearly appreciable on an occlusal radiograph. **Takeaway:** Cemento-ossifying fibromas cause significant jaw expansion and cortical thinning, which is well-demonstrated on occlusal radiographs. ## Case: Cemento-ossifying fibroma with jaw expansion ### Question **Scenario:** Occlusal radiograph of a cemento-ossifying fibroma. **What's shown:** Significant expansion of the jaw. **Consider:** What effect does this lesion have on the jawbone as seen on this view?    ### Answer **Observations:** - Marked expansion of the jaw is visible. **Reasoning:** Cemento-ossifying fibromas typically demonstrate cortical thinning and significant expansion, which is clearly appreciable on an occlusal radiograph. **Takeaway:** Cemento-ossifying fibromas cause significant jaw expansion and cortical thinning, which is well-demonstrated on occlusal radiographs. Case: Cemento-ossifying fibroma with jaw expansion Radiograph: Two periapical radiographs (labeled B and C) showing various bone patterns seen in ossifying fibroma. Panel B displays a mostly radiolucent area with wispy trabeculae indicated by an arrow, while Panel C shows a granular-like pattern with arrows pointing to the affected region near the maxillary sinus floor. A A periapical radiograph showing the mandibular premolar-molar region with teeth restored by radiopaque amalgam fillings. An arrow points to a well-defined, corticated lesion located between the tooth roots, which exhibits a characteristic wispy trabecular internal pattern. D Radiograph: An occlusal radiograph showing a lesion in the anterior palate/maxillary region. The image illustrates a flocculent pattern with larger tufts of bone formation, as indicated by the arrow. 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