A cerebral granular cell tumor in a cat.

A cerebral granular cell tumor is described in a 6-year-old, short-haired, female cat. The tumor was observed above the corpus callosum and completely infiltrating the third ventricle. Histologic examination revealed that the tumor was characterized by large cells containing densely packed intracytoplasmic granules and expressed psammoma body-like patterns and cholesterinic degeneration. Immunohistochemical analysis revealed granular neoplastic cells that were diffusely and strongly vimentin-positive, while they did not express cytokeratins, lysozyme, and synaptophysin. Based on morphologic and immunohistochemical findings, the tumor under study was considered to be of meningeal origin arising directly from the meninges or from meningeal elements scattered in the tela choroidea of the third ventricle roof.