Current therapeutic strategies for BC are based on tumor heterogeneity associated with different histotypes and specific molecular profiles: ER+ and PR+ patients are treated with hormonal therapy, HER2+ patients with anti-HER2 therapy, and BRCA mutation carriers with poly (ADP-ribose) polymerase (PARP) inhibitors plus adjuvant therapies (chemotherapy, immunotherapy, and radiation therapy) (5). The gene discussed is ESR1; the disease is breast cancer.