It remains to be investigated whether the HER2 amplification in these HER2 2 + DCIS has an important biological and clinical consequence, but until we have large-scale studies that can reliably provide these data, we could extrapolate the ASCO/CAP algorithm for HER2 assessment in invasive breast cancer to DCIS, and perform ISH on all DCIS with a HER2 2 + score. This evidence concerns the gene ERBB2 and invasive breast carcinoma.