Histopathological and Immunohistochemical Studies of Pineoblastoma in a Cow.

We report the first case of pineoblastoma in a cow. At necropsy, a soft, gelatinous greyish yellow, 4 × 3 × 2 cm mass was found midsagittally on the dorsal surface of the midbrain. The mass enveloped the brainstem anterior to the cerebellum, extended to the pituitary fossa and was adherent to the ventromedial aspect of the occipital lobes. Histologically, the mass was unencapsulated, with extramedullary proliferation into the lobes and meninges, but was demarcated from the adjacent brain tissue. Histological findings were consistent with a pineoblastoma, as reported in other species, and the neoplasm was strongly immunopositive for synaptophysin. Glial fibrillary acidic protein-positive spindloid astrocytic processes surrounded blood vessels and extended around neoplastic cells.