The study is open to men and women with HER-2/neu-overexpressing metastatic breast cancer. Concurrent hormone therapy and/or bisphosphonates (standard breast cancer therapy that is not chemotherapy or other investigational therapy) is allowed. Patients may have received Trastuzumab in the past or continue on it while participating in this study. About 40 people with HER-2/neu positive breast cancer will enter in the study. About 20 will pass the screening tests and receive the vaccine.