Triple-negative breast cancer (TNBC) is a particularly aggressive subtype of breast cancer that represents approximately 15–20% of all breast cancers diagnosed worldwide and is characterized by the absence of estrogen receptors (ER-), progesterone receptors (PR-), and human epidermal growth factor receptor 2 (HER2-), making it resistant to conventional hormonal therapies and targeted treatments [3]. The gene discussed is ESR1; the disease is breast cancer.