Piloleiomyosarcoma in seven ferrets

In each of seven ferrets (Mustela putorius furo) with leiomyosarcoma, a sin gle dermal mass was identified and biopsied. Each mass consisted of a well- demarcated but nonencapsulated proliferation of large spindle- to strap-sha ped cells arranged in interwoven bundles. The cells resembled the smooth mu scle cells of the adjacent arrector pili muscles, but with marked nuclear p leomorphism. Immunohistochemical staining for smooth muscle actin, desmin, and vimentin was positive and staining for myoglobin and cytokeratin was ne gative. Follow-up on three of the ferrets indicates that the prognosis is g ood following complete surgical excision.