Based on the molecular phenotype, breast cancer can be divided largely into luminal subtypes, which show relatively good responsiveness to treatment (15,16), and the basal-like subtypes, which represents 75% of the triple negative [estrogen receptor (ER)−, progesterone receptor (PR)−, Her2−], aggressive and invasive population (17) and 15–20% of breast cancers (18–20). This evidence concerns the gene ESR1 and breast cancer.