OUTLINE: This is a dose-finding study. Patients receive a test dose of borophenylalanine-fructose complex (BPA-F) for biodistribution studies and undergo punch biopses of tumor and normal tissue to measure B-10 concentration. Later, a treatment dose of BPA-F over 1 hour is followed by neutron irradiation. Groups of 3 patients receive escalated doses of neutron irradiation until the maximum tolerated dose is determined. Patients who complete protocol treatment and continue to meet the eligibility criteria may re-enter the study, provided at least 6 months has elapsed since the completion of prior therapy and the field boundary for the new irradiation site is seperated from the boundary of the previously irradiated site. Patients are followed monthly for 12 months, then every 3-6 months as needed.