Interestingly, 3 of 73 patients with DCIS/LCIS had 1 HER2-positive CTC/22.5 mL (4.1%, 95%CI 1.4–11.4%) and 8 of 101 patients with M0 BC had ≥1 HER2-positive CTC/22.5 mL (7.9%, 95%CI 4.1–14.9%, median 1 cell, range 1–3 cells). The gene discussed is ERBB2; the disease is ductal breast carcinoma in situ.