ERBB2 and ductal breast carcinoma in situ: Based on expression of the PAM50 genes, we determined the intrinsic subtypes using the widely used centroid based classifier27 (see “Methods”), which provided correlation coefficients to each of the four centroids; basal-like, HER2-enriched, luminal A and luminal B. We found a significantly different distribution of the subtypes between DCIS and IBC (P = 0.0016, Fisher’s exact test, Fig. 1a).