As HER2-positive DCIS are generally larger than HER2-negative DCIS (Table 1) [7, 11, 12, 21–24], it could be worthwhile to retrospectively determine the HER2 status in the Forget-Me-Not 2 study, to investigate its association with subsequent ipsilateral IBC. The gene discussed is ERBB2; the disease is ductal breast carcinoma in situ.