Triple-negative breast cancer (TNBC) is an invading type of heterogeneous phenotype breast cancer, which is diagnosed by the lack of progesterone receptor (PR), estrogen receptor (ER), and human epidermal growth factor receptor 2 (HER2), and reports for ~15% of all breast carcinomas.1 TNBC is more difficult to treat than the other types of breast cancer because hormone therapy is more common to target one of the above mentioned receptors. Here, ESR1 is linked to breast cancer.