Primary nervous system lymphoma in cats.

Here we characterize the neuroanatomic distribution, neuropathology, and immunophenotype of 10 cases of primary nervous system lymphoma in cats. Cases were retrospectively searched from 2 academic institutions. Selected cases were reviewed and subjected to immunohistochemistry (IHC) for CD3, CD20, and Pax5. The mean age of affected cats was 9.1 y, and no sex or breed predilection was observed. The most common clinical sign was ataxia (8 cases). Gross changes reported in 8 cases consisted of white-to-tan masses (7 cases) or swelling (1 case) within the neuroparenchyma (5 cases) or epidural spaces (3 cases). Histologically, intraparenchymal lymphomas occurred in the gray and white matter or perivascular spaces (7 cases); extraparenchymal lymphomas (6 cases) consisted of neoplastic cell infiltration of the perivascular spaces in the leptomeninges, choroid plexus, or epidural spaces. Nerve lymphomas were diffusely infiltrative. Tumors occurred in the brain (4 cases), spinal cord and nerves (3 cases), spinal cord (2 cases), and brain, spinal cord, and nerves (1 case). IHC was consistent with a B-cell lymphoma in 5 cases and with a T-cell lymphoma in 5 cases.