Breast tumors can be separated into different molecular subtypes: (1) the luminal A and B subtypes, overexpressing progesterone (PR) and/or estrogen receptors (ER), (2) the HER2 + subtype, expressing high levels of the human epidermal growth factor receptor 2 (HER2) protein and (3) the triple negative breast cancers (TNBC) expressing no PR and/or ER and without HER2 overexpression and/or amplification11–13. Here, ESR1 is linked to triple-negative breast carcinoma.