Compared with SLNB-negative patients, those with SLNB metastases more frequently harboured an intratumoural ductal carcinoma in situ (DCIS) component, showed higher ER/PR expression and lower Ki-67, and were predominantly luminal A or luminal B/HER2−, whereas AUS performance appeared more favourable in HER2-enriched and triple-negative tumours. This evidence concerns the gene ERBB2 and ductal breast carcinoma in situ.