Breast cancer is a collection of heterogeneous diseases that differ in molecular and phenotype, which can be divided into luminal A, luminal B, HER2- enriched, and basal-like subtypes based on the expression of hormone receptors including estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). This evidence concerns the gene ESR1 and breast carcinoma.