ESR1 and triple-negative breast carcinoma: Based on both molecular and histological evidences, BC could be categorized into three subgroups: BC expressing hormone receptor (estrogen receptor (ER+) or progesterone receptor (PR+)), BC expressing human epidermal receptor 2 (HER2+) and triple-negative breast cancer (TNBC) (ER-, PR-, HER2-) [2,3].