ESR1 and neoplasm: Consequently, diagnosis and the following appropriate therapeutic plan strictly depend on the integration of histological and molecular characteristics of the tumor, that take into the account grade, stage, lymphovascular invasion, and the presence of axillary lymph node metastasis, but also the status of steroid receptors [estrogen receptor (ER), progesterone receptor (PR)], human epidermal growth factor receptor 2 (HER2), and the Ki67 index (nuclear marker of proliferating cells) [4].