AbstractBackgroundAngiosarcoma of the breast is a rare malignancy. There are little data evaluating the survival and estimating the prognostic factors. The best surgical management and the role of systemic adjuvant therapy remain ill‐defined. This study aimed to investigate the clinicopathological features, survival, and prognostic factors of breast angiosarcoma.MethodsThe data on patients diagnosed with breast angiosarcoma were extracted from the Surveillance, Epidemiology, and End Results database (1975–2016). Univariate and multivariate Cox regression analyses were used to estimate the influential prognostic factors. The overall survival (OS) and disease‐specific survival (DSS) of patients with breast angiosarcoma were evaluated.ResultsThis study included 656 patients diagnosed with breast angiosarcoma between 1975 and 2016. The 5‐year OS rate of all patients was 44.9% (95% CI 40.8–49.0). In both OS and DSS, Kaplan–Meier survival analyses revealed significant differences for both OS and DSS according to age, year at diagnosis, laterality, grade, and stage (all log‐rankp< 0.05). Multivariate analysis suggested that lesions of the right breast, poor differentiation, and advanced stage were independent risk factors for OS or DSS (allp< 0.05). Older age was a risk factor in OS, but was protective in DSS. In primary breast angiosarcoma, age, laterality, grade, and stage were independent prognostic factors in OS and DSS (allp< 0.05). Mastectomy was also a risk factor in DSS (p= 0.034). The proportion of patients with grade III and regional disease was larger in the mastectomy group.ConclusionAngiosarcoma of the breast had a poor prognosis. In our study, age, laterality, histologic grade, and stage were identified as significant prognostic factors. Why patients with angiosarcoma of the right breast had a worse prognosis remains equivocal. Mastectomy was adopted more often by surgeons in this cohort study for patients with advanced primary breast angiosarcoma.