Multiple cutaneous mast cell tumors in a pig.

Cutaneous tumors are not usually observed in pigs, and mast cell tumors, in particular, have been rarely described. The current report describes numerous, pink to red, elevated, 1-5-cm nodules in the skin of a 6-month-old slaughter pig. The histopathology of the nodules revealed well-demarcated, but poorly differentiated, populations of round cells that extended from the dermis into subcutaneous tissues. The presence of eosinophils and the observation, at high magnification, of cells with cytoplasmic metachromatic granules, after toluidine blue staining, confirmed the diagnosis of multiple cutaneous mast cell tumors.