Breast cancer is a major healthconcern affecting more than 2 million women worldwide and its risingincidence and high mortality rates make it a major economic and socialburden.1−4 Breast cancer can be classified into 4 molecular subtypes basedon the presence or absence of estrogen receptor, progesterone receptors,and the human epidermal growth factor receptor 2 (HER2).2,5−8 Among these subtypes, breast cancer characterized by the overexpressionof HER2 is linked to lower survival rates, presenting significanttreatment challenges.9,10. The gene discussed is ESR1; the disease is breast cancer.