Among 691 BRCA1/2 mutation carriers, 233 women developed invasive breast cancer (111 and 122 with BRCA1 and BRCA2 mutations, respectively), and 15 patients had ductal carcinoma in situ (3 BRCA1 and 12 BRCA2 mutation carriers, respectively), whereas 7 women had invasive breast cancer and the other 3 women developed ductal carcinoma in situ, among 229 non-carriers. Here, BRCA1 is linked to ductal breast carcinoma in situ.