Theses subtypes include luminal A (ER+/HER2−/low levels of Ki-67 protein), luminal B (ER+/HER2−/+/high levels of Ki-67 protein), triple-negative/basal-like (ER−/HER2−), HER2 enriched (HR−/HER2+), and normal-like BC, which is similar to luminal A, but with poor prognosis [5]. Here, ESR1 is linked to breast cancer.