Myelopathy caused by a histiocytic sarcoma in a cat

An eight-year-old, female spayed, domestic shorthair cat presented with a three-week history of progressive general proprioceptive ataxia and upper motor neuron paresis of the hindlimbs. Computed tomography revealed a mediastinal mass invading the vertebral canal with the T1 spinal nerve and roots, causing extramedullary compression of the cranial thoracic spinal cord. Histopathological and immunohistochemical studies of the mass during postmortem examination disclosed a neoplasm, later determined to be a poorly differentiated histiocytic sarcoma. Feline histiocytic tumours are rare, with only two prior reports existing in the veterinary literature. This report details a case work-up and reviews the literature on feline histiocytic diseases and tumours affecting the feline spinal cord.