Primary T-cell lymphoma of the central nervous system.

We describe a 64-year-old man who presented with a 9-month history of a progressive neurologic disturbance affecting principally his short-term memory, eye movements, and sense of balance. Computed tomography and magnetic resonance imaging showed a 3-cm mass in the left cerebellar hemisphere. This was removed at craniotomy and proved histologically to be a diffuse non-Hodgkin's lymphoma. Further investigation showed no evidence of lymphoma elsewhere in the body. Immunohistochemical studies with an extensive panel of monoclonal antibodies showed the tumor cells to be T cells staining with the markers UCHL1, MT1, OKT3, and OKT11. Cells of the helper phenotype predominated. A small admixed reactive population of polyclonal B cells and macrophages was also present. The proliferation count as judged with the antibody Ki67 was about 15%. Primary cerebral lymphoma is in itself a rare entity with most cases being of B-cell origin. Primary cerebral T-cell lymphoma is extremely rare and the few previously reported cases are reviewed.