Piloleiomyosarcoma in seven ferrets

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