This groundbreaking discovery laid the foundation for the FDA approval of the p110α-specific inhibitor alpelisib to treat PIK3CA-mutated, hormone receptor-positive (HR+), epidermal growth factor receptor 2-negative (HER2−) breast cancer patients, in combination with fulvestrant, an antagonist of the estrogen receptor (ER).3 The gene discussed is ESR1; the disease is breast carcinoma.