Odontogenic Tumours Overview

Odontogenic Tumours

• Odontogenic tumours arise from tooth-forming tissues, ranging from benign (non-cancerous) to malignant (cancerous).
• They include neoplasms, hamartomas, and dysplasias.
• Classified based on resemblance to tooth development stages.

Tumour Classification (WHO)

• Group 1: Odontogenic epithelium without ectomesenchyme:
  • Ameloblastoma
  • Calcifying epithelial odontogenic tumour (Pindborg tumour)
• Group 2: Odontogenic epithelium with ectomesenchyme:
  • Ameloblastic fibroma, fibro-dentinoma, fibro-odontome
  • Odontome (complex & compound)
  • Adenomatoid odontogenic tumour
  • Calcifying odontogenic cyst
• Group 3: Odontogenic ectomesenchyme:
  • Odontogenic fibroma
  • Myxoma (myxofibroma)
  • Benign cementoblastoma (true cementoma)

Clinical and Radiographic Features

• Size and Site: Typically range from 1-20 cm, prevalent in jaw areas. Common clinical signs include swellings (intra/extra-oral), tooth displacement, unerupted teeth, and missing teeth.
• Radiological Features: Can appear unilocular (single chamber) or multilocular (multiple chambers). X-rays may reveal corticated (well-defined) edges, radiolucent (dark on X-rays), radiopaque (light on X-rays) internal structures. May also cause root resorption, bone destruction, and tooth displacement.

Benign Odontogenic Tumours

• Originate from various tissues linked to tooth development: dental lamina, rests of Serres, enamel epithelium, and Hertwig's root sheath.
• Categorized as epithelial, mixed epithelial-mesenchymal, or mesenchymal.

Malignant Odontogenic Tumours

• Rare, predominantly originating from odontogenic epithelium.
• Classified as carcinomas.
• Examples: ameloblastic carcinoma, primary intraosseous carcinoma, clear cell odontogenic carcinoma, odontogenic sarcomas (e.g., ameloblastic fibrosarcoma).

Tumour Development

• Histodifferentiation refers to the development of specialized cells (e.g., ameloblasts).
• Morphodifferentiation involves shape formation.
• Higher classification tumours show better histodifferentiation but less morphodifferentiation.

Key Structures Involved

• Key tissues involved in tooth development and potentially tumour formation include ameloblasts (enamel), dentine (tooth substance), reduced enamel epithelium, stellate reticulum, internal/external enamel epithelium, Hertwig's root sheath, dental papilla (dentine/pulp), and dental follicle.

Diagnostic Considerations

• Differential Diagnoses:
  • Infections (local, spreading)
  • Cysts (odontogenic/non-odontogenic)
  • Other tumours, giant cell lesions, fibro-osseous lesions.
• Important Diagnostic Features: Patient age/sex, lesion site/size/shape (uni/multilocular), radiodensity, presence/duration, and histopathological analysis (tissue examination).

Specific Tumours (Examples)

• Ameloblastoma: Commonest odontogenic tumour, benign but locally aggressive.
  • Commonly found in posterior mandible, ages 40-50, Afro-Caribbeans are more susceptible.
  • Radiologically appears as multilocular, expansile lesions.
  • Subtypes: solid/multicystic (conventional), unicystic (younger patients, associated with unerupted lower molars).
  • Histologically variable (follicular, plexiform, etc).
  • Genetic links (e.g., BRAF V600E, RAS, SMO, FGFR2 mutations).
• Myxoma: Gelatinous consistency, derived from dental papilla.

Other General Points

• Odontogenic tumours typically occur in tooth-bearing areas of the jaws.
• Tissue mineralisation of enamel or dentine-type can be observed.
• Accurate diagnosis through biopsy and histopathology is essential.