Amyloid-producing odontogenic tumor and its immunohistochemical characterization in a Shih Tzu dog

A 10-year-old, male, Shih-Tzu dog presented with swelling of the right lower jaw caused by a mass arising from the right mandibular gingiva. Radiographic examination revealed bone lysis of the right wing of the mandible. Histopathologically, the growth was characterized by indistinctly lobulated nests, islands, and strands of proliferating odontogenic and squamous epithelial cells, intermingled in close association with large numbers of irregular extracellular deposits of amyloid and amorphous calcified substance. Immunohistochemically, both epithelial components stained strongly positive for cytokeratin (AE1/AE3); the squamous epithelial cells also reacted strongly with neuron-specific enolase (NSE) and S-100 protein, whereas the odontogenic epithelial cells displayed weak immunoreactivity to NSE and partial reactivity to S-100 protein. The amyloid deposits were AE1/AE3-negative. The growth was diagnosed as an amyloid-producing odontogenic tumor.