ESR1 and breast cancer: Three Molecular subtypes of BC depending on estrogen, progesterone, and HER2 status were investigated in this study: luminal A (L. A): ER(+) and /or PR(+) Her2 (-), luminal B (L.B): ER(+) and /or PR(+) Her2 (+), triple-negative (T.N): ER(-) and /or PR(- ) Her2 (-) (Sadek et al., 2017).