Acanthomatous Ameloblastoma

Also known as: Acanthomatous Epulis — Peripheral Ameloblastoma — Basal Cell Carcinoma — Adamantinoma

Description

Ameloblastoma (Courtesy of Alun Williams (RVC))

This is a benign but locally invasive odontogenic tumour that appears in the gingiva, often surrounding and displacing the adjacent teeth. The lesions have a raised and sometimes cauliflower appearance and are slow growing. Eventually the lesions can become very large and involve the jaw bone.

Signalment

Common oral tumour in dogs but rarely occurs in cats.

Diagnosis

Clinical Signs

Include halitosis, oral bleeding, dental disruption or loss, facial or mandibular deformity, excessive salivation, growth protruding from the mouth and rarely dysphagia.

Diagnostic Imaging

Standard skull radiography is often unrewarding and of low diagnostic yield. Skull computed tomography (CT) provides much greater detail and is frequently employed in preoperative planning (in combination with standard dental intra-oral radiographs). Odontogenic neoplasms frequently are found to involve multiple teeth, contrast enhance, involve lysis of the alveolar bone and demonstrate mass-assoicated tooth displacement. Acanthomatous ameloblastomas may appear as extra-osseous or intra-osseous masses; intra-osseous masses are more likely to have mass-associated cyst-like structures and are subjectively more aggressive as compared to extra-osseous acanthomatous ameloblastomas. In many cases mandibular lymphadenopathy is also observed. In cases where a malignant neoplasm is suspected, complete staging should be performed to look for metastatic disease, including 3-view thoracic radiographs (or thoracic CT) and abdominal imaging (abdominal ultrasound or abdominal CT).

Biopsy

Required for a definitive diagnosis and incisional biopsy is the technique of choice. When undertaking cytological or grab procedures it is more difficult to obtain a representative sample.

Pathology: Islands and sheets of mature odontogenic epithelium within a collagenous fibrous connective tissue stroma of low/moderate cellularity will be noticed. Each of the islands is bounded by a row of tall columnnar cells. These palisading cells exhibit polarisation away from the basement membrane and have cytoplasmic vacuolation. Central cells have a basaloid appearance. The tumour is often infiiltrating into the underlying bone.

Treatment

Surgical resection is the best option with margins of at least 1cm. Radiation therapy may be considered in patients where wide surgical excision is not possible, however there is a risk of malignant transformation of the tumour at a later stage.

Prognosis

Good following complete surgical excision.

Acanthomatous Ameloblastoma Learning Resources
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References

Tutt, C., Deeprose, J. and Crossley, D. (2007) BSAVA Manual of Canine and Feline Dentistry (3rd Edition) BSAVA

Merck & Co (2008) The Merck Veterinary Manual

With thanks to Andrew Jefferies (Cambridge) and Alun Williams (RVC) for providing access to their lecture materials

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