A subependymal giant cell astrocytoma in a cat

A 6-year-old spayed female Domestic Shorthair cat presented with a 1 to 2-m onth history of blindness and altered behavior. At necropsy, a l-cm-diamete r, firm white mass was found arising from the subependymal region of the ri ght lateral ventricular wall that protruded into and partially filled the l umen. Histologically, there was a well-demarcated, expansile paraventricula r neoplasm composed of moderately pleomorphic cells within a richly fibrill ar matrix arranged in interlacing streams and perivascular pseudorosette-li ke patterns. Neoplastic cells varied in morphology from small spindloid cel ls to larger polygonal cells with eccentric vesicular nuclei to neuronlike cells with vesicular nuclei and prominent nucleoli. The mitotic index was l ow. Immunohistochemically, neoplastic cells were positive for S-100 protein , glial fibrillary acidic protein, and neuron-specific enolase and negative for neurofilament protein. Ultrastructurally, the cells contained few to a bundant bundles of intermediate filaments with variable numbers of mitochon dria, endoplasmic reticulum, and ribosomes. These features are characterist ic of subependymal giant cell astrocytoma (SEGA) in humans. To our knowledg e, this is the first reported case of SEGA in domestic animals.