Spontaneous ependymoma in a free-ranging juvenile black-horned capuchin (Sapajus nigritus).

A young free-ranging black-horned capuchin (Sapajus nigritus) with a history of ataxia, anisocoria, diminished threat and pupil reflexes and increased cranial circumference was referred for evaluation to the Medicine and Wildlife Conservation Section, Federal University of Paraná, Paraná, Brazil. Due to the clinical presentation and radiographic findings of hydrocephalus, euthanasia was performed. Necropsy revealed a dark red mass (1.5 × 1.8 cm) in the region of the third ventricle and marked dilation of the lateral ventricles. Histopathological findings were characterized by proliferation of ciliated round cells with eosinophilic cytoplasm, as well as the formation of ependymal rosettes and pseudorosettes. In some areas the cells contained brown cytoplasmic pigment, which stained with Fontana-Masson. The neoplastic cells were immunoreactive for glial fibrillary acidic protein and negative for pancytokeratin. Considering the anatomopathological and immunohistochemical findings, the diagnosis was ependymoma grade II with melanocytic features, which is the first report of this neoplasm in any member of the genus Sapajus.