“Triple-negative” [negative for estrogen receptor (ER−), progesterone receptor (PR−), and human epidermal growth factor receptor 2 (HER-2)] breast cancers (TNBCs) account for approximately 15 to 20% of all breast cancers and have the characteristics of heterogeneity, aggressiveness, and poor prognosis [1–3]. The gene discussed is ESR1; the disease is breast cancer.