ESR1 and triple-negative breast carcinoma: To better understand the behavior of MABC, we then divided MABC into 136 HER2-negative cases and 69 HER2-positive cases, since MABC subgroup included tumors with ER-/PR-/HER2- (triple-negative breast cancer, TNBC) and ER-/PR-/HER2+ (HER2-overexpression).