Since HER2 protein overexpression in DCIS is strongly associated with high grade atypia (Table 3) [7–9, 11, 12, 21–23, 26, 31, 42, 55], Van Seijen et al. investigated the addition of HER2 IHC to the reproducibility of histopathological grading [56]. The gene discussed is ERBB2; the disease is ductal breast carcinoma in situ.