11.3 Odontogenic & Non-Odontogenic Tumours

Odontogenic Tumours — WHO 2022 (5th edition)

The WHO 5th edition (2022) classification of odontogenic tumours introduced adenoid ameloblastoma as a new benign epithelial entity and applied essential and desirable diagnostic criteria to each entity. The major benign tumours you must know for MFDS Part 1 are below.

Ameloblastoma

• Benign but locally invasive odontogenic neoplasm.
• Site: mandibular molar / ramus region (~80%); less often maxilla (maxillary lesions behave more aggressively due to cancellous bone and proximity to sinonasal cavities).
• Mean age ~35; slight male predominance.
• Radiology: multilocular 'soap-bubble' radiolucency; can be unilocular; cortical expansion; root resorption; cortical perforation in advanced disease.
• Histology: follicular and plexiform patterns are the most common. Follicular shows islands of epithelium with peripheral tall columnar cells with reverse nuclear polarity and a stellate reticulum-like centre; cystic degeneration gives the soap-bubble quality.
• Subtypes: conventional (multicystic), unicystic (luminal, intraluminal, mural — mural recurs like conventional), desmoplastic (anterior maxilla, mixed radiolucent/radiopaque), extraosseous/peripheral (gingiva).
• Behaviour: high local recurrence if simply enucleated (cortical perforation and daughter islands). Resection with a 1–1.5 cm bony margin is the standard of care for conventional ameloblastoma. Unicystic luminal/intraluminal variants may be managed more conservatively.
• Exceptional 'malignant ameloblastoma' / ameloblastic carcinoma — very rare, with lung metastases reported.

Odontoma

• The most common odontogenic tumour (a hamartoma).
• Compound odontoma — multiple small tooth-like denticles; classical site anterior maxilla.
• Complex odontoma — haphazard calcified dental tissues; classical site posterior mandible.
• Radio-opaque mass with a radiolucent rim; often an incidental radiographic finding; sometimes associated with an impacted tooth.
• Management: enucleation; recurs only if incompletely removed.

Calcifying Epithelial Odontogenic Tumour (Pindborg Tumour)

• Rare, benign, locally invasive.
• Posterior mandible; often associated with an impacted tooth.
• Mixed radiolucent/radiopaque appearance; 'driven-snow' calcifications within the radiolucency.
• Histology: sheets of polyhedral epithelial cells, amyloid-like material, and Liesegang ring calcifications.
• Management: enucleation with a margin; recurrence is possible so long-term follow-up is needed.

Adenomatoid Odontogenic Tumour (AOT)

• Young patients (teens to 20s); female predominance.
• Classical site: anterior maxilla, often associated with an unerupted canine.
• Radiology: well-circumscribed unilocular radiolucency above the cementoenamel junction (cf. dentigerous cyst at the CEJ); focal calcifications.
• Histology: 'two-cell' ductal pattern — duct-like structures lined by columnar/ameloblastic epithelium with cuboidal cells.
• Behaviour: benign; cured by conservative enucleation.

Ameloblastic Fibroma

• Young children/adolescents; posterior mandible.
• Mixed radiolucent (epithelial component) and mesenchymal; resembles a developing tooth.
• Can recur; rare progression to ameloblastic fibrosarcoma is described.
• Conservative resection is debated; many units favour wider clearance than enucleation.

Cementoblastoma

• Benign tumour of cementum attached to the root apex; classical site mandibular molars.
• Radiopaque mass fused to the root; pain is often the presenting feature; the associated tooth is vital.
• Management: en bloc resection with the tooth if symptomatic.

Non-Odontogenic Tumours and Lesions

Osteoma

• Benign mature bone lesion; mandible, maxilla, paranasal sinuses.
• Multiple osteomas + intestinal polyposis = Gardner syndrome (a variant of familial adenomatous polyposis, FAP), caused by APC mutation. Also associated with supernumerary teeth, odontomas, and epidermoid cysts.
• Excise if symptomatic or disfiguring.

Central Giant Cell Granuloma (CGCG)

• Multilocular radiolucency, anterior mandible; 'honeycomb' pattern.
• Histology: osteoclast-like multinucleated giant cells in a fibrous stroma with haemosiderin.
• Critical differential: brown tumour of hyperparathyroidism is histologically identical — check serum calcium and parathyroid hormone (PTH) before biopsy. Treating the hyperparathyroidism resolves the brown tumour.
• Management options: intralesional steroids, calcitonin, bisphosphonates, denosumab, curettage, or resection depending on size and behaviour.

Fibro-Osseous Lesions

Langerhans Cell Histiocytosis (LCH)

• Eosinophilic granuloma is the solitary bone form (most benign presentation); children/young adults.
• Radiology: 'punched-out' radiolucency; alveolar form causes loosened 'floating teeth' and mimics periodontal disease.
• Histology: Langerhans cells with coffee-bean nuclei, positive for CD1a, CD68, S100; Birbeck granules on electron microscopy.
• Biopsy is essential; management varies from curettage to systemic therapy in multisystem disease.

MFDS diagnostic pearl: Any multilocular radiolucency of the jaws demands biopsy and a blood panel (calcium/PTH/alkaline phosphatase) before definitive treatment — the differential includes ameloblastoma, OKC, CGCG, brown tumour of hyperparathyroidism, and Langerhans cell histiocytosis.