The improvement in targeted therapeutic plans, such as cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors, phosphatidylinositol 3-kinase (PI3K) inhibitors, and selective estrogen receptor degraders (SERDs), has significantly expanded the treatment options for patients with estrogen or progesterone receptors and human epidermal growth factor receptor 2 (HR+/HER2-) breast cancer, leading to improved outcomes and a better understanding of the underlying molecular drivers of this disease [4]. This evidence concerns the gene ESR1 and breast cancer.