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14 October 2015 - Case of the Week #367

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Case of the Week #367

Clinical history:
A 12 year old boy had a radio-opaque / radiolucent process in the upper jaw close to the right maxillary tuberosity. The clinical impression was calcifying odontogenic tumor (Pindborg tumor) vs ossifying fibroma.

Gross description:
The specimen consisted of multiple bone fragments, the largest including a molar tooth, altogether ~8 ml in volume.

Micro images:








What is your diagnosis?



Odontoameloblastoma (OA) is an extremely rare and locally aggressive mixed odontogenic tumor with both epithelial and mesenchymal components. It is an ameloblastoma in which focal differentiation into an odontoma appears, and often occurs in association with an impacted tooth. OA affects young patients with a mean age of 20 years. This tumor usually occurs in the posterior segment of either jaw, with a slight inclination for the mandible (Oral Oncol 2002;38:800, Med Oral 2004;9:340). Several names exist for this tumor in the literature, including odontoblastoma (Thoma, 1970), adamant-odontoma (Shafer et al., 1983), calcified mixed odontogenic tumor (Hoffman, 1985), soft and calcified odontoma (Worleyand Mckee, 1972) and ameloblastic odontoma (Hooker, 1967).

Like ameloblastoma, the tumor presents as a centrally destructive lesion. Symptoms include slow, progressive swelling of the alveolar plates, dull pain, an altered occlusion, delayed eruption or impacted teeth (Br J Oral Maxillofac Surg 1990;28:347, Indian J Dent Res 2009;20:230). Radiological examination reveals a multilocular radiolucency with radiopaque areas resembling mature dental tissue. It commonly exhibits a well defined margin, displacing the surrounding erupted teeth (J Oral Maxillofac Pathol 2011;15:60).

Histopathology shows odontogenic epithelial cells arranged in the form of follicles. There are tall columnar ameloblast-like cells in palisaded arrangements with stellate reticulum-like cells in the center. Some cells may have more squamoid features and in areas a loose stellate component is present. Large masses of interwoven, eosinophilic dentin arranged in a haphazard pattern may be present. At the center of these variably sized cavities are calcified nodules.

The differential diagnosis includes calcifying ontogenic cysts, ameloblastic fibro-odontoma, developing complex odontoma and odontogenic ghost cell tumors (Oral Oncol 2002;38:800). OA tends to occur with equal frequency in the mandible and maxilla, while ameloblastoma is prevalent in the mandible. In addition, OA tends to produce bone expansion similar to ameloblastoma, while odontoma seldom produces swelling of the affected region.

Because OA expands by infiltrating between bony trabeculae and has a high rate of recurrence, it should be treated aggressively like conventional ameloblastoma with wide surgical excision. Close follow-up for at least 5 years is indicated due to risk of recurrence (Oral Oncol 2002;38:800).

Discussion by Dr. Jennifer R. Kaley, University of Arkansas for Medical Sciences (USA).

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