ERBB2 and breast cancer: The reduction in breast cancer mortality is mainly due to three factors: the widespread use of tamoxifen (which inhibits the influences of estrogen), the development and use of Herceptin (which is a monoclonal antibody that interferes with the HER2/neu receptor, thus selectively inhibiting the growth of breast cancer cells in about 25% of breast tumors) and mammography screening programs which has allowed the early diagnosis and treatment of many breast cancers.