2. Diagnosis: Patients must have neoplastic meningitis secondary to an underlying leukemia/lymphoma or a solid tumor (including primary CNS tumors or carcinomas of unknown primary site) for which there is no conventional therapy. Patients with CNS leukemia/lymphoma must be refractory to conventional therapy, including XRT (i.e., 2nd or greater relapse). Neoplastic meningitis is defined as follows: (a)Leukemia/Lymphoma: CSF cell count over 5/µL AND evidence of blast cells on cytospin preparation or by cytology or (b) Solid tumor: Presence of tumor cells on cytospin preparation or cytology OR the unequivocal presence of meningeal disease on MRI scans.