Breast cancer updated categorization has resulted in recognition of four distinct sub types, involving triple-negative breast cancer (TNBC), human epidermal growth factor receptor (HER2)-over-expressing, luminal A, as well as luminal B. TNBC, which lacks the expression of the estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2), makes up roughly 10–15% of breast cancer incidents (4). The gene discussed is ESR1; the disease is breast cancer.