Breast cancer is classified into different molecular subtypes based on the expression characteristics of estrogen and progesterone receptors (ER and PR) and human epidermal growth factor receptor 2 (HER2; ERBB2): Luminal A, Luminal B, HER2(+), and triple-negative breast cancer (TNBC) [2]. The gene discussed is ERBB2; the disease is breast carcinoma.