AIM: Breast-conserving surgery with radiation therapy is the primary treatment for ductal carcinoma in situ (DCIS). Re-excision is indicated when clear resection margins have not been achieved, although in some cases the procedure may be unnecessary as there is no residual tumor. The purpose of our three-Center retrospective study was to identify predictors of positive re-excision findings following breast-conserving surgery for DCIS. PATIENTS AND METHODS: A total of 285 patients underwent re-excision following conservative treatment for DCIS between 01/01/08 and 12/31/13 at three breast-cancer referral Centers. We conducted a retrospective, comparative review of the factors that differentiated patients with a residual tumor from those without. The study was based on clinical, radiological, surgical and pathological criteria. RESULTS: A total of 180 patients (63%) had residual tumor after conservative treatment. Six factors were predictive on univariate analysis: young age (p=0.025), non-menopausal status (p=0.016), absence of preoperative biopsy (p=0.0029), high nuclear grade (p=0.0181), lesion size \textgreater30 mm (p=0.032), and positive surgical margins (p=0.0016). Four factors remained independently predictive on multivariate analysis: non-menopausal status (p=0.0017), high nuclear grade (p=0.0031), lesion size \textgreater30 mm (p=0.012) and positive surgical margins (p=0.0013). We calculated a 93% probability of positive re-excision findings if all four factors were combined. On the other hand, if none of the factors were present, the rate fell to 18%. CONCLUSION: In cases of DCIS, where risk factors for both involved lumpectomy margins and recurrence are carefully studied, knowledge of the risk factors for residual tumor can help guide therapeutic choices