A subependymal giant cell astrocytoma in a cat

A 6-year-old spayed female Domestic Shorthair cat presented with a 1 to 2-month history of blindness and altered behavior. At necropsy, a 1-cm-diameter, firm white mass was found arising from the subependymal region of the right lateral ventricular wall that protruded into and partially filled the lumen. Histologically, there was a well-demarcated, expansile paraventricular neoplasm composed of moderately pleomorphic cells within a richly fibrillar matrix arranged in interlacing streams and perivascular pseudorosette-like patterns. Neoplastic cells varied in morphology from small spindloid cells to larger polygonal cells with eccentric vesicular nuclei to neuronlike cells with vesicular nuclei and prominent nucleoli. The mitotic index was low. 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 abundant bundles of intermediate filaments with variable numbers of mitochondria, endoplasmic reticulum, and ribosomes. These features are characteristic of subependymal giant cell astrocytoma (SEGA) in humans. To our knowledge, this is the first reported case of SEGA in domestic animals.