Several previous studies indicated that a number of risk factors, such as age at the time of diagnosis, body mass index (BMI), tumor size, primary tumor quadrant, molecular subtype, estrogen receptor (ER) status, progesterone receptor (PR) status, human epidermal growth factor receptor-2 (Her-2) status, and other clinical parameters were associated with ALN metastasis in breast cancer [15–19]. The gene discussed is ESR1; the disease is breast cancer.