ESR1 and breast cancer: The cohort included 6.6% (n = 28) Her2 + (HER2, ER- PR- HER2 +), 30.8% (n = 130) luminal A (LUMA, ER + HER2- Ki-67 < 20%), 37.4% (n = 158) luminal B (LUMB, ER + HER2- Ki-67 ≥ 20%), 7.1% (n = 30) luminal Her2 + (LUMHER2, ER + HER2 +), and 18% (n = 76) triple negative BC (TN, ER- PR- HER2-) (Table 1 and S1).