ERBB2 and ductal breast carcinoma in situ: Some studies report an even higher proportion of HER2 positivity in microinvasive cancer14 and, in preoperative tumour biopsies displaying DCIS, HER2 over-expression has been related to increased incidence of invasive carcinoma in the surgical specimen.15 Furthermore, HER2 positivity is associated with high-histopathological grade both in invasive cancer and in DCIS.16