OBJECTIVE Angiosarcoma of the breast can be divided into primary and secondary. The objective was to determine clinicopathologic factors associated with breast angiosarcoma and to compare primary versus secondary angiosarcoma. METHODS Breast angiosarcoma cases at Mayo Clinic from 1960 to 2008 were identified. Clinicopathologic factors were reviewed. Characteristics of primary and secondary angiosarcoma were compared. RESULTS Twenty-seven cases of primary angiosarcoma and 14 cases of secondary angiosarcoma were identified. The median age of primary angiosarcoma patients was lower than that of secondary angiosarcoma--43 years versus 73 years (P < 0.0001). Primary angiosarcoma more frequently presented with a mass, whereas secondary angiosarcoma presented with a rash (P < 0.0001). Median time from radiation to secondary angiosarcoma diagnosis was 6.8 years. Median tumor size was 7.0 cm for primary angiosarcoma and 5.0 cm for secondary angiosarcoma (P = 0.7). Tumors were high grade in 33% of primary angiosarcoma and 82% of secondary angiosarcoma (P = 0.02). Five-year survival for primary and secondary angiosarcoma was 46% and 69%, respectively (P = 0.8). CONCLUSIONS Primary angiosarcoma occurs in younger patients than secondary and more frequently presents with a mass. Mastectomy is the mainstay of treatment for breast angiosarcoma. Breast angiosarcoma is a rare malignancy with poor long-term prognosis.