characterised 13 commonly used GEMMs, including MMTV‐PyMT, MMTV‐Neu, and C3(1)/TAg and showed that none of the models represent a luminal A subtype, even though 50%−60% of DCIS lesions classify as luminal A.20This suggests that GEMMs mainly recapitulate more aggressive subtypes of breast cancer, with rapid progression to IDC. Here, ERBB2 is linked to ductal breast carcinoma in situ.