DISEASE CHARACTERISTICS: Newly diagnosed undifferentiated nonlymphoblastic non-Hodgkin's lymphoma (Burkitt's or non-Burkitt's) Newly diagnosed large cell lymphoma with CNS involvement Recurrent non-Hodgkin's lymphoma L-3 and B-cell leukemia included At least 1 of the following required: LDH at least 500 IU/liter (old method) or 2,000 IU/liter (new method) Bone marrow involvement (greater than 5% lymphoblasts) CNS involvement (lymphoblasts on CSF cytospin or intracranial mass on CT or MRI scan)