DISEASE CHARACTERISTICS: Histologically confirmed newly diagnosed primary central nervous system (CNS) lymphoma Patients who have inconclusive biopsy or who are not candidates for biopsy may be eligible provided they have a typical cranial MRI or CT scan (presence of hypo, iso, or hyperdense parenchymal contrast-enhancing mass lesions) to insure that leptomeningeal nonparenchymal lymphomas are not included Must meet at least one of the following criteria: Positive CSF cytology for lymphoma or a monoclonal lymphocyte population as defined by cell surface markers Biopsy of the vitreous or uvea demonstrating lymphoma Isolated CNS relapse of systemic non-Hodgkin's lymphoma allowed