Giant Thoracic Schwannoma in a Rhesus Macaque (Macaca mulatta)

A 15-y-old male rhesus macaque with a 3-d history of labored breathing, was culled from a nonhuman primate research colony after thoracic radiographs and exploratory surgery revealed a 10-cm, well-circumscribed space-occupying mass in the posterior thoracic cavity. The multilobulated cystic and necrotic neoplasm was composed of interlacing streams and fascicles of neoplastic spindle cells arranged in Antoni A, and less commonly, Antoni B patterns. Verocay bodies were present also. The neoplasm was encapsulated mostly, and histomorphologic features were benign. Immunohistochemistry indicated that neoplastic cells were positive for vimentin, S100, glial fibrillary acidic protein, and nerve growth factor receptor. Reticulin histochemical staining and immunohistochemical stains for collagen IV and laminin showed a prominent basal lamina surrounding the neoplastic cells. The histologic features and results of the immunohistochemical stains confirmed peripheral nerve origin and were consistent with schwannoma. To our knowledge, this is the first case of thoracic schwannoma in a rhesus macaque and the second reported case of schwannoma in a nonhuman primate.