Mixed germ cell tumour of the spinal cord in a young dog.

A spinal cord mixed germ cell tumour was identified in a two-year-old, female Airedale terrier with a history of progressive paraplegia. At necropsy, a discrete pale pink spinal cord mass was identified at the L5 vertebra, which extensively invaded the associated spinal cord segments L6 and L7. Histologically, the tumour was located within the subarachnoid space and invaded the spinal cord. It was composed of three different types of cells: small round cells, forming clusters or islands, similar to germ cells identified in testicular germinomas; large cells with eosinophilic or amphophilic cytoplasm, forming trabeculae; and a third, rarer type of well differentiated epithelial cells, forming acinar or tubular structures. Immunohistochemical examination revealed reactivity to antibodies against alpha-fetoprotein and broad spectrum cytokeratins. The composition, cytological features and immunohistochemical staining of this neoplasm are similar to germ cell tumours previously reported in the suprasellar region and in the eye of dogs.