A 69-year-old otherwise healthy woman was diagnosed with early estrogen-receptor (ER) positive, Her2-negative (ER+Her2−) breast cancer (BC) at the age of 47 (in 1998) and was treated at a different hospital with lumpectomy, adjuvant chemotherapy, radiation, and adjuvant tamoxifen. This evidence concerns the gene ESR1 and breast carcinoma.