SURF4 and breast cancer: The age [hazard ratio (HR): 2.317, 95% confidence interval (CI): 1.452-3.699, P < 0.001], stage (HR: 2.090, 95% CI: 1.585-2.755, P < 0.001), and SURF4 expression (HR: 1.958, 95% CI: 1.230-3.115, P = 0.005) exhibited independent prognostic value for OS of breast cancer.