Metastases of a pheochromocytoma involving the central nervous system in adog

A seven-year-old female Cavalier King Charles presented a left oculomotor n erve palsy and a rapidly evolving flaccid paraplegia. On necropsy, a necrot ic mass replaced the right adrenal gland almost completely, and tumours wer e observed in the liver, kidneys and lungs. A tumoural invasion of the righ t renal vein and the right trunk of the internal vertebral venous plexus at the caudal lumbar level were disclosed. Two tumours were present on the du ra-matter at the level of the left cerebral hemisphere and a subarchnoidal tumour compressed the left oculomotor nerve. Ail tumoural locations exhibit ed the same histological features. Argyrophilic granules were demonstrated in the tumoural cell cytoplasm and immunohistochemical staining for neurone specific enolase was positive. This malignant neurosecretory tumour was cl assified as a phaeochromocytoma on the basis of the microscopic and biochem ical features and the involvement of one adrenal gland. The concurrent tumo ural invasion of a renal vein and of the vertebral venous plexus has not ye t been described in the dog and suggests that a retrograde venous spread th rough the vertebral plexus may have contributed to the central nervous syst em involvement in this dog.