ERBB2 and ductal breast carcinoma in situ: Intriguingly, ductal carcinoma in situ (DCIS), which is deemed to be the precursor lesion of invasive ductal cancer, has a much higher rate (50–60 %) of HER2 amplification and overexpression than that of invasive breast cancer, which is about 25 % positive for HER2 [13–15].