According to the molecular analysis of these markers, such as estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), and Ki-67, breast cancer can be divided into luminal A, luminal B, HER2 overexpression, and basal-like subtypes that are related to different biological characteristics and treatments [1]. The gene discussed is ESR1; the disease is breast carcinoma.