Moreover, the ROC curve analysis revealed that serum miR-21 levels could distinguish patients with HER2− (AUC  = 0.763, p = 0.001) and HER2+ (AUC  = 0.804, p<0.0001) breast cancer from HDs; whereas serum miR-10b levels could distinguish patients with HER2+ from patients with HER2− breast cancer (AUC  = 0.749; p = 0.0003) and HDs (AUC  = 0.756; p = 0.0001) (Figure S4). Here, ERBB2 is linked to breast cancer.