Clinicopathological Characteristics and Prognosis of Squamous Cell Carcinoma of the Breast: A Population-Based Analysis

BACKGROUND: To better understand the clinicopathological features and prognostic profiles of squamous cell carcinoma (SCC) of the breast. METHODS: Information on breast cancer was obtained from the Surveillance, Epidemiology, and End Results database (2004–2016). Comparative analyses were carried out to investigate the heterogeneity in the clinicopathological characteristics and survival outcomes between SCC and invasive ductal carcinoma (IDC), while propensity score matching was conducted to analyze the variations among baseline characteristics. Prognostic factors for SCC of the breast were successively identified using Cox regression analysis. RESULTS: A total of 382 SCC patients and 561477 IDC patients were identified in this study. Comparatively, the SCC cohort exhibited a higher proportion of male individuals, poor differentiation, an advanced TNM stage, an increasing percentage of triple-negative (TN) subtype, an increasing rate of organ involvement, and less access to therapeutics. The aggressive profile was consistent in the TN subgroup, with a significantly higher proportion in SCC than in IDC (25.7% vs 6.8%). Prognosis of SCC was profoundly poorer than that of IDC (mOS, 78.6 months and 121.6 months, P < .0001; mBCSS 91.9 months vs 135.6 months, P < .0001), of which the inferior tendency remained stable among disease stage and therapeutic options, while no difference was detected in the 2 subgroups with the TN subtype. The 2-year survival rate was 66.9% and the 5-year survival rate was 51.4%, with the risk factors being older age, bilateral disease, advanced TNM stage, bone and visceral involvement, surgical intervention, radiation treatment, and chemotherapy. CONCLUSIONS: This study systematically analyzed the heterogeneous characteristics of SCC of the breast in comparison with IDC. Squamous cell breast cancer presented with increasing aggressive behavior and inferior prognosis. Prospective studies should focus on this subgroup and introduce individualized therapeutic protocols in clinical practice.