AMELOBLASTOMA

AMELOBLASTOMA

DEFINITION:-

 Ameloblastoma is defined as "usually unicentric, non-functional, intermittent in growth, anatomically benign  and clinically persistent". -Robinson

PATHOGENESIS:-

The tumor may derive from the:

1. Cell rest of enamel organ, either remnants of dental lamina or remnants of Hertwig’s sheath, the epithelial rest cells of Malassez

2. Epithelium of odontogenic cyst, i.e. dentigerous cyst or odontomas

3. Disturbance of the developing enamel organ

4. Basal cell of the surface epithelium of the jaw

5. Heterotrophic epithelium in other parts of body specially in pituitary gland.

CLINICAL FEATURES:-

- Ameloblastoma occurs in 2nd, 3rd, 4th and5thdecade oflife

- Mean age of occurrence is 32 years

- Males are affected more commonly than females.

- Ameloblastoma in most of the cases involves mandible in molar ramus area

- Clinically ameloblastoma presents slow enlarging, painless, ovoid and fusiform bony hard swelling of the jaw

- Pain, paresthesia and mobility of regional teeth is present in some cases

- Pathological fractures may occur in many affected bones.

GROSS APPEARANCE:- 

Grossly the tumor is grayish white, usually solid, sometimes cystic, replacing and expanding the affected bone.

HISTOPATHOLOGY:-

Histologically the ameloblastoma shows neoplastic proliferation of odontogenic epithelial cells mostly in four distinct patterns.

1. Follicular type

2. Plexiform type

3. Acanthomatous type

4. Granular type.

Follicular Type

- The neoplastic odontogenic epithelial cells proliferate in form of multiple discrete follicles and islands within fibrous connective tissue stroma.

- Each follicle like structure is bordered on the periphery by the single layer of all columnar cells resembling ameloblasts.

- The cells located at the center of follicle are loosely arranged and resembles stellate reticulum cells. Microcyst formation is often observed inside these follicles.

Plexiform Type

- This pattern of neoplastic cell proliferation is also often called as fish net like pattern.

- Peripheral layer of cells are tall columnar in nature and often resemble ameloblastoma.

- Cells situated at center portion of strands resemble stellate reticulum.

- The intervening connective tissue stroma is thin with minimum cellularity and shows multiple areas of cystification which may be either large or small in number.

Acanthomatous Type

- The cells occupying the position of the stellate reticulum undergoes squamous metaplasia, sometimes with keratin formation in the anterior portion of tumor islands.

- Occasionally, epithelial or keratin pearls may be observed

-  Areas of calcification may be found in the metaplastic squamous epithelium.

- It may be confused with the squamous cell carcinoma. 

Granular Type

- There is marked transformation of the cytoplasm, usually of the stellate reticulum like cells that it takes a very coarse granular eosinophilic appearance.