Compounds and methods for the treatment and diagnosis of breast cancer are provided. The inventive compounds include polypeptides containing at least a portion of breast tumor antigen. Vaccines and pharmaceutical compositions for immunotherapy of breast cancer comprising such polypeptides, or polynucleotides encoding such polypeptides, are provided, together with polynucleotides for preparing the inventive polypeptides. The inventive polypeptides may be used to generate antibodies useful for the diagnosis and monitoring of breast cancer.