Resumo
Schwannoma is a peripheral nerve sheath tumor (PNST), commonly found as a spindle cell tumor of autonomic nerves and rarely involving the skin of cattle. The present report describes the histopathology and immunohistochemistry features of a localized (solitary) benign PNST with final diagnosis of cutaneous schwannoma in a 4-year-old female Holstein bovine. The dome-shaped, well circumscribed, firm, non-smooth surfaced mass was composed of spindle-shaped cells arranged predominantly in interlacing fascicles or streams with a moderate to strong intervening collagenous stroma. Histopathologic changes included typical hypocellular areas with pale scant eosinophilic cytoplasm (Antoni B pattern) similar to myxomatous tissue, and hypercellular areas with deeply eosinophilic cytoplasm (non-typical Antoni A pattern) without nuclear palisading or Verocay bodies formation. Immunohistochemical reactions for S-100 protein, a Schwann cell marker, and vimentin were strong in the neoplastic cells. Other markers as desmin, neuron specific enolase (NSE), CD34, and p53 were all negative. It was concluded that concurrent evaluation of both histological and immunohistochemical features are required for the final diagnosis of schwannomas in domestic animals