ERBB2 and ductal breast carcinoma in situ: When it came to adjuvant treatment, the proportion of use of chemotherapy increased from 4.2% in pure DCIS to 19.3% in DCIS-Mi and to 45.9% in DCIS-T1a (P<0.001), mainly in patients with TNBC, HER2-positive or node-positive tumors.