Ependymal cyst in the cerebrum of an African green monkey (Chlorocebus aethiops).

A focal lesion was detected by magnetic resonance imaging in the right caudal occipital lobe of the cerebrum in an African green monkey (Chlorocebus aethiops). Neurological signs were not observed in this animal. At necropsy examination, an 8mm wedge-shaped intracranial cavity was found, which apparently did not communicate with the ventricles. Microscopically, the inner surface of the cavity was lined by ciliated cuboidal epithelium with positive immunoreactivity for S100 protein, glial fibrillary acidic protein and cytokeratin. Based on the gross, microscopical and immunohistochemical findings the lesion was classified as an ependymal cyst. To the best of our knowledge, this is the first report of an ependymal cyst in an African green monkey.