Clinical applications of systemic adjuvant therapy indicate that endocrine therapies are only effective in HR-positive cases while trastuzumab (a humanized monoclonal anti-HER2 antibody) is only active in ERBB2 amplified or HER2 over-expressed patients, and cytotoxic chemotherapy will benefit more in triple negative (TN) breast cancer, which lacks expression of ER, PR and HER2 protein [8]. This evidence concerns the gene ESR1 and breast cancer.