ESR1 and triple-negative breast carcinoma: Breast cancer is the most commonly diagnosed malignant tumor in women worldwide [1] and it is generally classified based on classical immunohistochemistry markers such as estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2): luminal (A and B), HER2-positive, and triple-negative breast cancer [2].