ERBB2 and ductal breast carcinoma in situ: Some studies suggest that patients with HER2 amplified DCIS are more frequently high-nuclear grade and this aspect is related to an increased risk of relapse.54,55 In fact, some studies suggest that HER2 plays a major role in the transition from DCIS to IDC,18,56 while others do not support this.9,57 In the current study, HER2 amplification was more frequent in the pure DCIS cohort (20%) than in the mixed DCIS (15%) despite the more prevalent higher-grade DCIS in the mixed cases.