MUC1 and breast cancer: Current methods for breast cancer diagnosis mainly depend on serological (cancer antigen 15-3, carcinoembryonic antigen, tissue polypeptide antigen, tissue polypeptide-specific antigen) and pathological observations.28 However, cancer antigen 15-3 and carcinoembryonic antigen show low positive rates (15%) for the early diagnosis of breast cancer and are not recommended by the American Society of Clinical Oncology and European Society for Medical Oncology.