Squamous Odontogenic Tumour

Definition:
It is a  benign epithelial odontogenic tumour.

 Histogenesis:
1. Cell rests of Malassez: Source of epithelial proliferation for lesions associated with alveolar process adjacent to lateral roots.

2. Dental lamina: For lesions associated with crowns of unerupted or impacted tooth.

Clinical features:
Age: 11 - 67 years, M>F
Site: Mandible: Bicuspid-molar area (more common)
        Maxilla: Incisor-cuspid area
Asymptomatic lesions but can show:
  - Mobility of involved teeth
  - Pain, tenderness on percussion
  - Occasionally, abnormal sensations

Radiologic features:
Not significant
- Presents as semicircular or roughly triangular radiolucent area, with or without sclerotic border, usually in association with cervical portion of the root.

Histologic features:

- Consists of islands of mature squamous epithelium without peripheral columnar layer. Peripheral layer is flat or cuboidal.
Squamous  cells are uniform with prominent intercellular bridges (no pleomorphism, no nuclear hyperchromatism, no mitotic activity)
- Sometimes, individual cell keratinization but no epithelial pearls
- Microcyst formation (in small portion epithelial islands)
- Lamellar calcification
- globular, hyaline, eosinophilic structure within islands (not amyloid)
- Fibrous stroma

Histologic differential diagnosis:
1. Acanthomatous ameloblastoma
2. Desmoplastic ameloblastoma
3. Squamous cell carcinoma

Note:
Desmoplastic ameloblastoma VS Squamous odontogenic tumour:
Desmoplastic and acanthomatous ameloblastoma exhibit squamous differentiation within tumour islands but there is significant ameloblastic changes of the peripheral cells like columnar shape, nuclei away from basement membrane, vacuolated or clear cytoplasm and also the islands or strands are thin and compressed in desmoplastic ameloblastoma rather rounded and broad-based as seen in squamous odontogenic tumour.

Well differentiated squamous cell carcinoma VS Squamous odontogenic tumour:
Islands in squamous odontogenic tumour are well defined and cells lack variation in cell size, shape and nuclear staining and mitotic figures, which are characteristics of squamous cell carcinoma.

MCQS From Squamous Odontogenic Tumour: CLICK HERE