RESUMEN
Primary non-Hodgkin's lymphoma of the brain is a rare malignancy and there are known to occur almost exclusively in brain parenchyme. Recent immunological advances and immunohistochemical techniques have provided new insights into the pathogenesis and diagnosis of the malignant lymphoma even in the small biopsied tissue and the majority of these CNS tumors is thought to be derived from B lymphocytes. A 22-year old man was admitted due to headack, dizziness and walking difficulty for 2 months. On the initial CT scan, there were two enhancing lesion in the suprasellar area and pineal gland which were completely disappeared with steroid therapy and three new lesions appeared on the follow-up CT and MRI studies in corpus callosum, third ventricle and left cerebral peduncle. The serial cytologic smears of cerebrospinal fluid and a stereotaxic biopsy tissue from the corpus callosum mass showed diffusely homogenous infiltration of neoplastic large noncleaved lymphocytes with focal perivascular arrangement. On the immunocytochemical stains, the reaction was negative for GFAP, positive for LCA and MB2, and negative for MT1. After radiation therapy, the masses completely disappeared on the follow-up CT scan and the patient was discharged free of all the clinical symptoms.