Correlation plots and heatmaps of the in situ samples using the classifiers obtained after cross-validation. (a) Well- (n = 6) versus poorly (n = 14) differentiated ductal carcinoma in situ (DCIS). The classifiers consist of 43 genes. (b) Well-/well-intermediately (n = 16) versus intermediately-poorly/poorly (n = 20) differentiated DCIS using a classifier of 78 genes. i-p, intermediately-poorly differentiated; p, poorly differentiated; w, well differentiated; w-i, well-intermediately differentiated.