ESR1 and breast carcinoma: The current treatment options for breast cancer depend on the broad classification of breast cancer into (i) estrogen receptor α (ERα)-positive, progesterone receptor (PR)-positive; (ii) human epidermal growth factor receptor 2 (HER2) enriched, and (iii) triple negative breast cancer (TNBC) that do not express any of these three receptors [10,11,12,13].