 - Relapsed or refractory primary central nervous system CNS diffuse large B cell lymphoma PCNSDLBCL with a CNS lesion, with cerebrospinal fluid CSF relapse with positive CSF cytology, or with ocular relapse with positive ocular tissue biopsy; NOTE: tissue biopsy is not absolutely necessary for CNS tumor unless clinical and radiologic findings strongly suggest other etiologies as per treating physician; initial diagnosis must be made by tissue biopsy; NOTE: patients with B-cell lymphoma with features intermediate between diffuse large B-cell lymphoma and Burkitt lymphoma are also eligible for the protocol as long as they meet other criteria; patients with typical Burkitt lymphoma are not eligible 