Ductal carcinoma in situ (DCIS) is a frequent disease, concerning more than 15% of all breast carcinomas in France. Frequency increases due to breast screening programs. Breast conservative treatment can be done for limited lesions. Complete pathological excision with safe surgical margins is the main factor of success rate for conservative treatment. But safe surgical margins are not always obtained in the first surgery because preoperative or peroperative evaluation of the extent of the lesions is difficult. A 20 to 38% rate of involved margins is reported in the literature, implying a second surgery. MRI is not commonly performed today in the preoperative staging of DCIS, despite interesting results of breast MRI in DCIS evaluation published recently in a German study (Kuhl, Lancet 2007). Nevertheless, this retrospective study focused on a population of high-risk women (BRCA1-2 mutation carriers, family history of breast cancer…).