ESR1 and breast carcinoma: Unlike the estrogen receptor (ER)-positive and human epidermal growth factor receptor 2 (HER2) positive subtype, the biology of TNBC includes a high proliferation activity, a high degree of immune infiltration, basal-like or mesenchymal phenotypes, and insufficient homologous recombination (Denkert et al., 2017); its characteristics, including the risk factors, molecular and pathological characteristics, disease course, and sensitivity to chemotherapy, are distinct from those of other breast cancer subtypes (Borri and Granaglia, 2020).