In a cohort of 4573 high-risk women (954 BRCA1 carriers, 598 BRCA2 carriers, 3021 BRCA1/2 non-carriers) and 14,142 rounds with MRI between 2006 and 2015, 221 primary BCs (185 invasive, 36 ductal carcinomas in situ [DCIS]) were diagnosed within 12 months of annual screening. The gene discussed is BRCA1; the disease is ductal breast carcinoma in situ.