A canine peripheral nerve sheath tumor including peripheral nerve fibers

Peripheral nerve sheath tumor was found in a 7-year-old male mongrel dog. T he tumors were located in the right cheek subcutis and oral submucosa. Hist ologically, neoplastic cells were arranged in streaming bundles, occasional ly interlacing bundles or whorls of elongated and spindle cells. Cellular a typia was poor and mitotic figures were rarely observed. Ultrastructurally, neoplastic cells had basement membrane, typical of Schwann cells. One bund le of normal peripheral nerve fibers and some myelinated axons were seen wi thin the tumor tissues. Immunohistochemically, neoplastic cells reacted to vimentin, glial fibrillary acidic protein, S-100 protein and neuron specifi c enolase. In addition to the above immunoreactions, the included nerve fib ers were positive for myelin basic protein and neurofilament protein. This paper also discusses immunohistochemical findings on differential diagnosis in comparison with those of canine hemangiopericytomas reported hitherto.