Plasmacytoma in a Dog

History: 15-year-old neutered male dog, showing a pedunculated, red, firm mass attached to the dorsal aspect of the rectum.

Cytological description: The smears show multiple discrete medium-sized round to oval cells. These are characterized by a moderate amount of moderately basophilic cytoplasm with distinct cell borders, one eccentrically placed medium-sized round nucleus with coarse granular chromatin, occasional poorly-defined nucleoli, and mild to moderate anisocytosis and anisokaryosis.

Comments: Plasmacytomas are benign tumors of plasma cell origin. The lesion is usualy isolated, nodular, and 1-2 cm in diameter. It is mainly found on the trunk, the limbs, and the head. This tumor is rare in the cat. Surgical resection is usualy curative. Few cases of recurrence and metastasis have been reported.

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