Triple-negative breast cancer (TNBC) that represents 12-17% of all breast cancers (BC) is defined by less than 1% of the estrogen receptor (ER) and progesterone receptor expression, and normal human epidermal growth factor receptor 2 (HER2) gene copy number and expression (1).TNBCs have more aggressive behavior than non-TNBCs. The gene discussed is ESR1; the disease is breast cancer.