Accordingly, breast tumors were classified into five intrinsic subtypes with distinct clinical outcomes: luminal A (estrogen receptor (ER)+, progesterone receptor (PR)+, HER2− and Ki67 < 14%), luminal B (ER+, PR+, HER2− and Ki67 ≥ 14% or ER+, PR+, and HER2+), HER2-enriched (HER2+, ER− and PR−), basal-like (ER−, PR− and HER2−) and normal-like tumors [2,3,4,32]. This evidence concerns the gene ESR1 and breast neoplasm.