Peripheral primitive neuroectodermal tumour in a dog.

A 1-year-old German shepherd dog was presented with paraparesis quickly progressing to paraplegia. Magnetic resonance imaging revealed a large mass beneath the thoracolumbar vertebral column infiltrating the spinal canal and resulting in severe extradural compression of the spinal cord. Microscopically, this comprised a cell-rich unencapsulated tumour supported by fine bands of a fibrovascular stroma and occasionally forming primitive rosettes. Immunohistochemistry showed the tumour cells to express synaptophysin and neuron-specific enolase. Ultrastructurally, the neoplastic cells had low to moderate numbers of intracytoplasmic neurosecretory granules. A peripheral primitive neuroectodermal tumour was diagnosed. This is a rare embryonal tumour of neural origin that may have arisen from adrenal medulla, autonomic ganglia or peripheral nerves.