IntroductionBreast angiosarcoma is a rare malignancy of endovascular origin, accounting for less than 1% of all mammary cancers. Our aim was to explore clinicopathological features and the factors associated with prognosis.MethodsWe extracted information from the Surveillance, Epidemiology, and End Results Program (SEER) for all patients with breast angiosarcoma between 2004 and 2015. Chi-square analysis was used to compare the clinicopathological features in all patients. Overall survival (OS) was assessed using the Kaplan and Meier method. Univariate and multivariate analyses were performed to evaluate the factors associated with prognosis.ResultsA total of 247 patients were included in the analyses. The median OS of patients with primary breast angiosarcoma (PBSA) and secondary breast angiosarcoma (SBAB) was 38 months and 42 months, respectively. The 1-, 3- and 5-year OS with PBSA was 80%, 39%, and 25%, respectively, and the 1-, 3- and 5-year OS with SBAB was 80%, 42%, and 34%, respectively. Multivariate analysis revealed that tumor size (p= 0.001), tumor grade (p< 0.001), tumor extension (p= 0.015), and tumor spread (p< 0.001) were statistically significant factors for OS. Partial mastectomy with radiation (HR = 0.160, 95% CI, 0.036–0.719,p= 0.016), partial mastectomy with chemotherapy (HR = 0.105, 95% CI, 0.011–1.015,p= 0.052), and partial mastectomy (HR = 0.125, 95% CI, 0.028–0.583,p= 0.007) were related to significantly better OS outcomes in primary angiosarcoma.ConclusionPrimary breast angiosarcoma has a better clinical phenotype than secondary breast angiosarcoma. Although overall survival was not statistically significant, primary breast angiosarcoma was better than secondary breast angiosarcoma with systemic therapy. Depending on the outcome of survival, partial mastectomy is effective in treating primary breast angiosarcoma.