Trastuzumab, Cyclophosphamide, and Vaccine Therapy in Treating Patients With High-Risk or Metastatic Breast Cancer

DISEASE CHARACTERISTICS: * Histologically confirmed adenocarcinoma of the breast, meeting one of the following criteria: * Metastatic disease * High-risk disease, defined as early-stage disease with pathologic involvement of locoregional lymph nodes * Patients who are/will be receiving standard adjuvant trastuzumab \[Herceptin®\] for high-risk disease will participate in this study during the single-agent trastuzumab portion of their therapy * No clinical or radiographical evidence of active disease * Not eligible for therapy of known curative potential for metastatic breast cancer * HER2/neu-overexpressing disease, defined as HER2/neu positive by IHC 3+ staining or by FISH+ amplification * Stable CNS disease allowed provided it has been adequately treated and is not under active treatment * Hormone receptor status not specified PATIENT CHARACTERISTICS: * Menopausal status not specified * ECOG performance status 0-1 * ANC \> 1,000/mm\^3 * Platelet count \> 100,000/mm\^3 * Serum creatinine \< 2.0 mg/dL * Serum bilirubin ≤ 2.0 mg/dL (unless elevation is due to known Gilbert's syndrome) * AST/ALT ≤ 2 times upper limit of normal (ULN) * Alkaline phosphatase ≤ 5 times ULN * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception * Cardiac ejection fraction normal by MUGA OR ≥ 45% by ECHO * No other malignancies within the past 5 years, except for carcinoma in situ of the cervix, superficial nonmelanoma skin cancer, or supe…