BACKGROUND AND PURPOSE: Breast sarcoma (BS) is a rare tumour. While surgical resection is the primary treatment, the role of radiation therapy (RT) and chemotherapy remains unclear. This study aimed at defining prognostic factors and treatment strategies. MATERIALS AND METHODS: Data from 103 patients treated between 1976 and 2002 were collected. The median age was 55years (range: 13-86); the median histological tumour size was 4.45cm (range: 0.8-22). There were 42 angiosarcomas. Surgery consisted of wide excision in 34 cases, and total mastectomy in 69 cases. A total dose of 50Gy in 25 fractions was delivered in 50 patients. At the completion of treatment, 89 patients had no residual tumour. RESULTS: After a median follow-up of 64 months, 56 patients developed recurrent disease: 38 presented a local relapse and 37 developed distant metastases. The 5-year disease-free survival (DFS) and overall survival (OS) were 44% (95% confidence interval [CI], 39-49%) and 55% (95% CI, 50-60%), respectively. In multivariate analysis, favourable prognostic factors for better local control were: no residual tumour after treatment, no cellular pleomorphism, and histology other than angiosarcoma. For DFS, the five favourable prognostic factors were non-menopausal status, no residual tumour after treatment, non-angiosarcoma histology, absence of tumour necrosis, and grade 1-2 histology. CONCLUSION: While angiosarcoma has the worst prognosis, the outcome of the other types of sarcomas may be worsened by residual tumour after loco-regional treatment and high grade histology, a classical prognostic factor of the other soft tissue sarcomas. During surgical procedure axillary dissection is not mandatory.