White-matter abnormalities in unirradiated patients cured of primary central nervous system lymphoma

On MRI, primary brain tumors are commonly seen as contrast-enhancing masses surrounded by areas of abnormal signal on T2-weighted images. Following su ccessful treatment tumors may no longer show contrast enhancement. The resi dual abnormalities are assumed to be represent "edema" and infiltrating tum or cells. We report nine patients with primary lymphoma of the central nerv ous system who had complete responses to intravenous methotrexate, but did not receive intrathecal chemotherapy or cranial irradiation. After complete resolution of contrast-enhancing lesions, persistent abnormalities on T2-w eighted images in the region of prior tumor were initially assumed to refle ct residual viable tumor. As they remained unchanged for years, however, th is may not hold true in the cases in which primary central nervous system l ymphoma responds to chemotherapy alone.