Subject Inclusion Criteria:

          -  Patients must have a histologically confirmed diagnosis of a malignancy known to be
             8H9 reactive. 8H9 expression must be confirmed by immunohistochemical staining of
             tumor and assessed by the Department of Pathology or by immunofluorescence of bone
             marrow except for patients confirmed to have neuroblastoma.

          -  Patients must have CNS/ leptomeningeal disease which is refractory to conventional
             therapies or for which no conventional therapy exists OR a recurrent brain tumors with
             a predilection for leptomeningeal dissemination (medulloblastoma, PNET, rhabdoid
             tumor).

          -  Patients must have no rapidly progressing or deteriorating neurologic examination.

          -  Patients must have an absolute neutrophil count (ANC) > 1000/ul and a platelet count >
             50,000/ul.

          -  Patients may have active malignancy outside the central nervous system.

          -  Both pediatric and adult patients of any age are eligible.

          -  Patients or a legal guardian will sign an informed consent form approved by the IRB
             and obtained by the Principal or a Co- Investigator before patient entry. Minors will
             provide assent.

          -  Patients with stored stem cells will be treated at the escalating dose while patients
             with no stem cells will be treated at the 50 mCi dose. Neuroblastoma patients can be
             treated at the 50 mCi dose with or without stored stem cells.

        Subject Exclusion Criteria:

          -  Patients with obstructive or symptomatic communicating hydrocephalus.

          -  Patients with an uncontrolled life-threatening infection.

          -  Patients who are pregnant: Pregnant women are excluded for fear of danger to the
             fetus. Therefore negative pregnancy test is required for all women of child-bearing
             age, and appropriate contraception is required during the study period.

          -  Patients who have received cranial or spinal irradiation less than 3 weeks prior to
             the start of this protocol.

          -  Patients who have received systemic chemotherapy (corticosteroids not included) less
             than 3 weeks prior to the start of this protocol.

          -  Severe major organ toxicity. Specifically, renal, cardiac, hepatic, pulmonary, and
             gastrointestinal system toxicity should all be less than grade 2. Patients with stable
             neurological deficits (because of their brain tumor) are not excluded. Patients with
             <= 3 hearing loss are not excluded.