Periventricular spread of primary central nervous system T-cell lymphoma in a cat.

A 9-year-old domestic shorthaired cat with clinical signs of neurological disease was determined to have primary T-cell lymphoma of the central nervous system (CNS) on necropsy examination. Microscopically, neoplastic lymphocytes were distributed in the CNS parenchyma bilaterally around the cerebral ventricles, third ventricle, mesencephalic aqueduct, fourth ventricle and central canal of the spinal cord. The neoplastic infiltration was associated with complete loss of ependymal cells and marked astrocytosis. A large, solitary neoplastic lesion was present in the parenchyma around the central canal of the spinal cord at the level of the 13th thoracic vertebra. Immunohistochemically, the majority of neoplastic cells expressed CD3 and many also labelled for proliferating cell nuclear antigen (PCNA) and Ki-67. This is, to our knowledge, the first report of periventricular spread of primary CNS T-cell lymphoma in animals.