Ameloblastoma

Case contributed by Dr Henry Knipe

Presentation

Jaw pain and swelling.

Patient Data

Age: 50 years
Gender: Male
X-ray

Large expansile lytic lesion centred on the left mandibular angle with erosion of the 36-38 dental roots. 

CT

Large expansile lytic lesion centred on the left mandibular angle with cortical thinning and areas of cortical breach. Internally the mass is of heterogeneous soft tissue density. Erosion of 36-38 dental roots. 

MRI

Expansile lesion centred on the left mandibular angle with cortical destruction. Internally it is heterogeneously T1 hypointense / T2 hyperintense with peripheral post contrast enhancement, which is nodular posteriorly. Extra-osseous extension into the adjacent soft tissue. No enlarged lymph nodes. 

The patient underwent a left mandibulectomy.

Histopathology

MACROSCOPIC DESCRIPTION: A segmental mandibulectomy with the left first, second and third molar teeth.  It measures 60mm from the anterior bone margin to the posterior bone margin, the left coronoid process is included, making the specimen 70mm superior to inferior. The normal appearing bone is 12mm medial to lateral anteriorly, 8mm medial to lateral posteriorly.  A smooth, hard, multilocular cystic tumour expands the mandible and shows a smooth contiguous appearance with the adjacent periosteum.  The tumour is 50mm superior to inferior, 45mm anterior to posterior and 29mm medial to lateral. Around the three intact molar teeth there is a rim of smooth mucosa, measuring 33mm anterior to posterior and 22mm medial to lateral. There is a papilliform nodule, 7x4mm, between the gingiva and the
second and third molar on the lateral side.  The external surface of the bony periosteum and the surface of the tumour appears smooth. There is a flap of muscle at the lateral surface of the bone 55mm superior to inferior, 45mm anterior to posterior and approximately 10mm thick.  A scant amount of wispy skeletal muscle is also seen over the tumour on the medial surface posteriorly.  The margins are inked medial is blue and lateral is black.

MICROSCOPIC DESCRIPTION: Sections show a circumscribed tumour comprising microcysts
surrounded by nests and tongues of epithelium with thickened basement membrane, pallisaded basal cells with subnuclear vacuole, loose oedematous stellate-reticulum, and luminal squamoid cells with focal eosinophils, neutrophils and necrosis. No mucinous cells, mucin pools or mature keratin are seen.  The epithelial component is surrounded by dense fibrous stroma. The tumour shows no infiltrative pattern and has a pushing border. No poorly differentiated areas or separate tumour foci are seen. The tumour replaces and expands the bony medulla and the bony cortex appears thinned. The mandible shows mature lamellar bone with normal osteoblasts in lacunae. The teeth, skeletal muscle and salivary glands are not involved by the tumour. The features are consistent with a conventional ameloblastoma.

DIAGNOSIS: Conventional ameloblastoma 50x45x29mm, clear margins 0.5mm medial margin, 1mm lateral margin.

Case Discussion

Typical multimodality imaging features of an ameloblastoma. 

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Case information

rID: 53230
Case created: 7th May 2017
Last edited: 26th Sep 2017
System: Head & Neck
Inclusion in quiz mode: Included

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