ERBB2 and ductal breast carcinoma in situ: Over the course of the last few decades, the incidence of DCIS has significantly increased.33 This increase results in the overtreatment of patients in whom DCIS will not progress to IDC,34 indicating a clear need for predictive markers of disease progression.35, 36 HER2/neu occurs in up to 50% of in situ and only 25% of invasive ductal carcinomas,37 suggesting that additional alterations are required to transform DCIS into invasive disease.