ESR1 and breast cancer: Women are severely impacted by it, and the incidence rate ascends with age: over 80% of breast cancer (BC) cases are identified in women above 50 years old.[1] Clinically, specific subtypes of BC are defined based on their histopathological manifestations and the expression of hormone receptors and growth factors (such as the estrogen receptor, the progesterone receptor, and the human epidermal growth factor receptor 2[2,3]).