The pathological type, histopathological classification, histological grade, axillary lymph node status (ALN), lymphovascular invasion status (LVI), and immunohistochemical factors such as estrogen receptor (ER) and progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), and the Ki-67 proliferation index affect the prognosis of breast cancer (2–5), and these methods of evaluating the breast cancer prognosis are obtained invasively via biopsy. Here, ESR1 is linked to breast cancer.