We suggest that, in a given high-grade DCIS lesion with a low PR level and high Ki67 expression, there is a 56% probability that the lesion is a HER2-enriched subtype and a 79% probability of HER2 overexpression (score 3+) (OR: 2.325; 95% CI: 1.229 to 4.518). This evidence concerns the gene ERBB2 and ductal breast carcinoma in situ.