ESR1 and breast cancer: At present, traditional prognostic indicators include the patient’s age, the TNM stage (tumor-lymph nodes-metastases), the histological grade, the estrogen receptor (ER), the progesterone receptor (PR), and the human epidermal growth factor 2 (HER2) status, all of which are employed as prognostic indicators for breast cancer (Xie et al., 2022).