Triple-negative breast cancer (TNBC) is a special molecular subtype of breast cancer (BC) with unique biological and clinicopathologic characteristics, defined as estrogen receptor (ER)-, progesterone receptor (PR)-, and human epidermal growth factor receptor 2 (HER-2) - negative, representing 15-20% of BC cases (1, 2). The gene discussed is ESR1; the disease is breast carcinoma.