In China, BC mortality ranks first among women with malignant tumors, and it is the second leading cause of cancer-related death for women worldwide, accounting for roughly 15% of all female cancer deaths [2,3]. Nearly 70% of BC patients are estrogen receptor (ER)-positive (ER+) [4], making them eligible for endocrine therapies such as tamoxifen, fulvestrant, and letrozole [5]. Tamoxifen, a selective estrogen receptor modulator, competitively binds to the ER and inhibits ER-induced BC cell growth. The gene discussed is ESR1; the disease is breast cancer.