On the other hand, gene alterations of TP53, ESR1, GATA3, KMT2C, NCOR1, AKT1, NF1, RIC8A, and RB1 were more frequently observed in metastatic breast cancer compared with those in early breast cancer in hormone receptor-positive, HER2-negative disease7. The gene discussed is ESR1; the disease is breast carcinoma.