11.3 Odontogenic & Non-Odontogenic Tumours
Key Takeaways
- Ameloblastoma is benign but locally invasive; it arises in the mandibular molar/ramus region, shows a multilocular 'soap-bubble' radiolucency, and requires resection with a 1–1.5 cm bony margin rather than enucleation
- The WHO 5th edition (2022) added 'adenoid ameloblastoma' as a new benign epithelial odontogenic tumour and applies essential and desirable diagnostic criteria to each entity
- Multiple jaw osteomas with intestinal polyposis indicates Gardner syndrome (a variant of familial adenomatous polyposis, APC mutation), with implications for colorectal cancer surveillance
- A multilocular anterior mandibular radiolucency could be a central giant cell granuloma or the brown tumour of hyperparathyroidism — check serum calcium and parathyroid hormone before biopsy
- Langerhans cell histiocytosis (eosinophilic granuloma) gives 'punched-out' radiolucencies and 'floating teeth' and is confirmed histologically by CD1a-positive Langerhans cells with Birbeck granules
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
| Lesion | Key features |
|---|---|
| Fibrous dysplasia | 'Ground-glass' radiology; monostotic (most common) or polyostotic (McCune-Albright, GNAS mutation, café-au-lait macules); 'shepherd's crook' deformity of the femur; no surgical cure; biopsy for diagnosis |
| Ossifying fibroma | Well-demarcated; can be enucleated; cemento-ossifying variant (juvenile active ossifying fibroma is more aggressive) |
| Cemento-osseous dysplasia | Periapial (anterior mandible) — florid variant is multifocal; observe unless symptomatic or infected |
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.
A 40-year-old presents with a multilocular 'soap-bubble' radiolucency in the mandibular ramus with cortical expansion. Incisional biopsy shows epithelial follicles with peripheral tall columnar cells showing reverse nuclear polarity and a stellate reticulum-like centre. What is the most appropriate definitive management?
A 17-year-old female has a well-circumscribed unilocular radiolucency above the cementoenamel junction associated with an unerupted maxillary canine. Histology shows a 'two-cell' ductal pattern with duct-like structures. What is the most likely diagnosis?
A 25-year-old man is referred with multiple mandibular osteomas, supernumerary teeth, odontomas, and a family history of colorectal polyps. What is the underlying syndrome and gene mutation?
A 30-year-old female presents with a multilocular radiolucency in the anterior mandible. Histology on biopsy shows osteoclast-like multinucleated giant cells in a fibrous stroma. Which blood test is essential before definitive diagnosis and treatment?
A 12-year-old presents with a 'punched-out' radiolucency in the mandible with loosening of associated teeth ('floating teeth'). Biopsy shows cells with coffee-bean nuclei positive for CD1a and S100, with Birbeck granules on electron microscopy. What is the diagnosis?