Cutaneous Pigmented Neurofibroma in a Pig - Morphology and Immunohistochemical Profile.

Peripheral nerve sheath tumours are rare in pigs. In the present case, a juvenile female hybrid pig showed a solitary, pigmented, cutaneous mass. Histologically, it consisted of clustered melanin-laden, epithelioid cells as well as spindle cells forming bundles and nodules. The latter were surrounded by perineurial-like cells. Single Wagner-Meissner-like corpuscles were present. Immunohistochemically, the epithelioid cells expressed S100 protein, melan A and the p75 neurotrophin receptor (p75). The spindle cells expressed S100, sex determining region Y-box 2, p75, Krox20, growth associated protein 43 and glial fibrillary acidic protein. Perineurial-like cells were positive for p75, α-smooth muscle actin and cytokeratin. Taken together, the histological und immunohistochemical findings support the diagnosis of a cutaneous pigmented neurofibroma.