The management of pure ductal carcinoma in situ (DCIS) involves local excision, with or without consecutive radiotherapy, or simple mastectomy. Assessment of the recurrence risk is the essential step in decision-making. The hypothesis of this study was that besides the apparition of true recurrences after prior complete excision there may be also cases with residual disease present distant from the initial excised lesion (more than 2 mm). The last ones could be better considered as being cases of evolving disease. To evaluate the presence of residual disease in the re-excision specimens derived either from mastectomies or wide local re-excisions, a cohort of 102 cases of DCISs, operated in "Prof. Dr. Ion Chiricuta" Oncology Institute, Cluj-Napoca, Romania, between 2000 and 2007, were studied. The presence of residual tumor in re-excision specimens was correlated with high grade of DCIS and with age of the patient (less than 60 years). The analysis of mastectomy specimens revealed that 35.4% of all mastectomies had no residual disease (unnecessary mastectomies). Moreover, 59.8% of them had no residual disease or only close residual disease, virtually curable by simple re-excision. This study suggests that up to 59.8% of mastectomies could be avoided. Important is to select those cases in which avoiding mastectomy may be done assuming an acceptable recurrence risk. The study shows that those cases are from over 60-year-old group and those having histological grade G1. Larger prospective studies are needed to confirm the results of this study.