Cohorts of 3-6 patients receive escalating doses of pre-resection interleukin-13 PE38QQR immunotoxin until the histologically effective concentration (HEC) is reached or maximum tolerated dose (MTD) is determined. The HEC is defined by pathologic observations. The MTD is defined as the dose preceding that at which 2 of 6 patients experience dose-limiting toxicity. After the HEC is reached or MTD is determined, up to 6 additional patients are enrolled at selected dose levels to study safety and tolerability. Subsequent cohorts of patients are not treated with a pre-resection infusion.