Breast cancer can be categorized into four distinct molecular subtypes, namely luminal A, luminal B, HER2-enriched, and triple negative (TN) subtypes, according to the expression status of hormone receptors (HR), including estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) [23,24]. Here, ESR1 is linked to breast cancer.