In addition, BC is a heterogenous disease composed of three distinct subtypes (hormone receptor expression with different molecular characteristics and genetic profiles, including estrogen receptor (ER+) or progesterone receptor (PR+), human epidermal receptor 2 expression (HER2+), and triple negative BC (TNBC) (ER−, PR−, HER2− [2, 3]. This evidence concerns the gene ESR1 and breast cancer.