Immunoblastic sarcoma (histiocytic lymphoma) of the brain with B cell markers. Case report.

A group of central nervous system neoplasms, previously known as reticulum cell sarcoma or microglioma, and recently classified as malignant lymphoma, histiocytic type, not infrequently occur in patients with immunodeficiency, either primary or induced by immunosuppressant drugs. The authors report such a neoplasm in a patient with idiopathic thrombocytopenic purpura immunosuppressed with azathioprine and prednisone. The neoplasm was studied with several immunological techniques and by electron microscopy. The neoplasm had B lymphocyte membrane markers and showed plasmacytic differentiation. These features suggest that it was a tumor of transformed B lymphocytes (immunoblasts).