Clinicopathological characteristics and survival outcomes in breast carcinosarcoma: A SEER population-based study

OBJECTIVES: Carcinosarcoma of the breast is a rare disease. Its clinicopathological features and prognosis are not well defined. The aim of this study was to compare the clinicopathological features and clinical outcome between breast carcinosarcoma and breast invasive ductal carcinoma (IDC). MATERIALS AND METHODS: Patients with breast carcinosarcoma and breast IDC were identified through the Surveillance, Epidemiology, and End Results (SEER) database from 2010 to 2015. Then a comparison was conducted between these two groups. Propensity score matching (PSM) was performed to balance the effects of baseline clinicopathological differences. The Cox proportional hazard model was used to identify potential prognostic factors of breast carcinosarcoma. RESULTS: In total, we identified 63 patients with breast carcinosarcoma and 200,596 cases with breast IDC. Comparing with IDC, breast carcinosarcoma was significantly correlated with higher grading, higher staging, larger tumor size, lower lymph node involvement, and a higher proportion of triple negative breast cancer (TNBC), suggesting a significantly worse clinical outcome. After adjusting for the uneven clinicopathological variables with PSM, significant differences were still observed between these two histology types. Subgroup analysis further showed that carcinosarcoma-TNBC has an inferior clinical outcome compared with IDC-TNBC. Finally, we identified independent prognostic factors, namely, stage, tumor size, and distant metastasis. CONCLUSION: It is concluded that breast carcinosarcoma has distinct clinicopathological features and a significantly worse clinical outcome than common IDC.