ERBB2 and breast cancer: To quantify the accuracy of signature scores in classifying mutant versus wild-type samples, we determined the receiver operating characteristic (ROC) curves for the TP53_mut (Fig 2F) and ERBB2_amp (Fig 2G) signatures in multiple ER+ breast cancer datasets (TP53: GSE3494 and GSE22093, ERBB2: GSE 22358 and GSE22597).