Histopathology Session 2 DENT4217 Odontogenic tumours **A/Prof Omar Kujan** **Case 1** * Slide ID 642 * Image 439 X-ray image of jaw with a multilocular radiolucency, likely consistent with an odontogenic keratocyst or ameloblastoma. Histological image showing glandular or epithelial tissue under a microscope (H&E stain).  Here is the text from the image, formatted as requested: **and here are the different crops of this image to help you see better, use these only as hints:**  # **Microscopic features** * Odontogenic epithelial islands composed of: * Peripheral palisading columnar cells at basal layer, hyperchromatic * Cells show reverse polarization away from basement membrane (Vickers-Gorlin change) * Stellate reticulum-like cells, suprabasal cells composed of loosely arranged angular cells * No dentin or enamel formation * Many subtypes known and are most commonly described in the context of conventional ameloblastoma (likely have no prognostic significance) * **Follicular**: most common subtype; islands of odontogenic epithelium in fibrous connective tissue; may be cystic * **Acanthomatous**: squamous metaplasia and variable keratinization of stellate reticulum-like cells * **Plexiform**: cords and sheets of anastomosing odontogenic epithelial cells * **Granular cell**: granular eosinophilic cytoplasm often located within stellate reticulum-like cells * **Basaloid**: least common variant; nest or islands of hyperchromatic basal cells without stellate reticulum-like cells * Macrocystic degeneration of the tumor islands may occur. When a portion of this phenomenon is sampled for biopsy, the appearance may suggest a cyst, a unicystic ameloblastoma or cystic CCOT * Used to be called "cystic ameloblastoma" but use of this terminology is discouraged as may be confused with variants of unicystic ameloblastoma * **Desmoplastic variant**: dense collagenous stroma with compressed, angular islands of odontogenic epithelium <span style="color:rgb(59,85,208);">**Diagnosis**</span> * Ameloblastoma (follicular type) # Differential diagnosis - Differential diagnosis of conventional multicystic ameloblastoma - **Malignant ameloblastoma** - Also called metastasizing ameloblastoma - Identical histology but with metastasis - **Ameloblastic carcinoma** - Variable features of amelobastoma: peripheral palisading, reverse polarization, stellate reticulum - Features of malignancy include cytological atypia, high N:C ratio, increased mitoses with atypical forms, necrosis - Can also metastasize - **Ameloblastic fibroma** - Histologically, may share same features within the odontogenic epithelial component strands, cords and islands that may exhibit peripheral palisading, reverse polarization and stellate reticulum - Stroma is essential to the diagnosis and appears more primitive, delicate and lobular in appearance - **Adenomatoid odontogenic tumor** - Benign tumor of odontogenic epithelium with basaloid duct-like nest or cords lined by cuboidal or columnar cells. - Can have focal reverse polarity, like ameloblastoma - Duct-like spaces contain eosinophilic secretions and amyloid-like material may be present - 2/3 are female, usually occurs in 2nd decade in anterior maxilla - **Squamous odontogenic tumor** - Benign tumor of odontogenic squamous epithelium - Very rare; thought to arise from rests of Malassez in periodontal ligament - **Should not have peripheral palisading or stellate reticulum** - **Calcifying cystic odontogenic tumor (CCOT)** - Benign cystic tumor of odontogenic origin aka “Gorlin cyst” or “Calcifying odontogenic cyst” - Can have “ameloblastic” features: columnar or cuboidal basal cells with lumen lined by tissue resembling stellate reticulum - Will have ghost cells or anucleate epithelial cells - In cases exhibiting predominantly cystic architecture, differential includes - **Dentigerous cyst** - **Variants of unicystic ameloblastoma** - **Cystic CCOT** - A sampling of the macrocystic degeneration of a conventional ameloblastoma - **Case 2** - Slide ID 880 - Image 331 Histological image of lymphoid tissue with germinal centers, likely showing reactive follicular hyperplasia.  Here is the original image: and here are the different crops of this image to help you see better, use these only as hints:  Here is the original image: and here are the different crops of this image to help you see better, use these only as hints:  **Microscopic features** * Well circumscribed, central proliferation of ductlike epithelium surrounding small foci of calcification * Epithelium may have rosettes, trabecular or cribriform patterns * Columnar type cells with basal nuclei and clear cytoplasm may resemble pre-ameloblasts * Eosinophilic fibrillar material is present between tumor cells and within ductlike structures * Rarely melanin deposition **Diagnosis** * Adenomatoid odontogenic tumour **<font color="#4472c4">Differential diagnosis</font>** - **<font color="#4472c4">Dentigerous cyst</font>** - **<font color="#4472c4">Odontogenic cyst</font>**