Objectives: To conduct a survey of the angiosarcomas developing after breast conservation for carcinoma in the French Cancer Centers, to study the evolution of these cases in detail, and to review literature in an attempt to propose an optimal treatment scheme. Material and Methods: Eleven of the 20 French Cancer Centers agreed to research and retrospectively analyze all angiosarcomas discovered in patients previously treated by conservative treatment. The majority of the patients were node negative, T1N0M0. The mean age of the patients at the time of primary breast cancer treatment was 62.5 years, and 69 years at the diagnosis of the angiosarcoma. Results: During the last two decades, nearly 20,000 patients have been treated conservatively in these 11 centers, and only 9 cases of angiosarcoma were found. The median latency period between the treatment of the breast carcinoma and the diagnosis of the breast angiosarcoma was approximately 74 months, with a range of 57–108 months. Mastectomy was performed as the main treatment of this angiosarcoma. All recurrences after mastectomy for the angiosarcoma appeared within 16 months after the mastectomy. A median time of recurrence was found to be 7.5 months, regardless of the treatment. The angiosarcomas appeared to be very aggressive, and chemotherapy, radiotherapy, and sometimes hyperthermia could only palliate the condition for a short time. After the diagnosis of angiosarcoma, the median survival was 15.5 months, showing a particularly poor prognosis. Only 1 patient of 9 is alive without progressive disease at 32 months after salvage mastectomy for the recurrence of the angiosarcoma. Precise data obtained from 11 centers show that, of 18115 breast carcinomas treated conservatively, only 9 breast angiosarcomas are reported, which represents a prevalence of 5 cases of angiosarcoma per 10,000, which is the same prevalence for primary breast angiosarcomas occurring in healthy breasts. Conclusion: Angiosarcoma developing after breast conserving therapy for carcinoma is a rare event, and induction of it by treatment is controversial. However, early diagnosis is essential and it appears that radical mastectomy gives the highest chance of cure and the best long-term survival.