The HER-2/neu oncogene is amplified and overexpressed in 20-40% of interductal carcinomas of the breast and 30% of ovarian cancers. Overexpression of the protein in both these malignancies is associated with aggressive disease and is an independent predictor of poor prognosis in several subsets of patients. Some patients with breast cancer have existent T cell and antibody immunity to HER-2/neu. HER-2/neu is a self-protein. Therefore, it had been assumed that patients would be immunologically tolerant and that immunity could not be generated.