© 2015, Hare et al.; licensee Springer. Purpose: Primary small cell carcinomas of the breast (SCCB) are rare tumors with limited data on outcomes and treatment strategies. Using a population based approach, we aimed to study outcomes of SCCB and determine whether the use of radiation therapy is associated with better survival among patients with SCCB. Methods: Using the Surveillance, Epidemiology and End Results (SEER) registry, we identified patients with SCCB between1973 and 2010. We examined the stage specific survival of these patients and compared it to the stage specific survival of small cell lung cancer (SCLC) from the SEER database over the same accrual period. We further analyzed the impact of radiation therapy on overall survival for SCCB patients using a univariate and multivariate approach. Results: A total of 199 patients with primary SCCB with staging were identified during the study period. Eighty-four patients (42%) had localized disease, 77 (39%) had regional disease and 38 (19%) had distant disease. For comparison, 81,933 patients with SCLC were identified. Outcomes were superior for patients with SCCB with localized (150 vs. 16 months, p < 0.01) and regional disease (56 vs. 13 months, p < 0.01), but not distant disease (7 vs. 7 months, p = 0.43). Use of radiation therapy was not associated with a significant difference in OS for patients with either localized (202 vs. 147 months, p = 0.48) or regional (52 vs. 75 months, p = 0.650) disease. Conclusions: SCCB has a more favorable prognosis by stage for localized and regional disease than SCLC. Adjuvant radiation is not associated with an improvement in survival for patients with localized or regional SCCB in this dataset.