ESR1 and breast cancer: Breast cancer treatment primarily consists of breast-conserving surgery, mastectomy with adjuvant radiotherapy and chemotherapy, and the use of targeted therapies for various types of breast cancer, such as trastuzumab, which can significantly improve the survival rate of patients with HER2-positive breast cancer [8], and the selective estrogen receptor modifier (SERM), which binds to estrogen in a competitive manner and inhibits cell proliferation and growth [9].