DISEASE CHARACTERISTICS: Histologically confirmed neoplasm that is recurrent in the subarachnoid space Biopsy of recurrent lesion required if original diagnosis made more than 2 years prior to entry and CSF cytology negative Radiographic evidence of measurable lesion in the leptomeninges (by myelography, CT, or MRI) or cytologic evidence of malignancy in the CSF Any type of neoplasm eligible provided tumor cells (tissue or CSF preparation) bind significantly to intact monoclonal antibody Me1-14 IgG2a or to Me1-14 F(ab')2 Patency of subarachnoid pathways demonstrated by isotopic intraventricular flow