ESR1 and triple-negative breast carcinoma: Although a majority of basal-like tumors carry a clinical triple-negative phenotype (TNP) (ER-, progesterone receptor-negative (PR-), and HER2-), they are not synonymous [30], and triple-negative breast cancers include many cases that lack the expression of basal markers - the so-called 'five-marker negative phenotype' (5NP): ER-, PR-, HER2-, epidermal growth factor receptor-negative (EGFR-), and cytokeratin (CK) 5/6- - which have been shown to have significantly better outcomes than core basal cases [31,32].