Based on molecular marker expression, BC is divided into subtypes as follows: hormone receptor (HR)-positive subtype (estrogen receptor (ER +) or progesterone receptor (PR +)), human epidermal growth factor receptor 2 overexpression subtype (HER2 +), and triple-negative breast cancer (TNBC) (ER − , PR −, HER2 −) [3]. Here, ESR1 is linked to breast cancer.