These subtypes include luminal A and B (positive for estrogen receptor (ER) and/or progesterone receptor (PR)), human epidermal growth factor 2-positive (HER2+) (high expression of the HER2 oncogene) and basal-like breast cancer (BLBC, expressing genes specifically of the basal cells of the normal breast) [4],[5]. This evidence concerns the gene ESR1 and breast cancer.