Statistical analyses
The differences of clinicopathologic characteristics between SCS and non-SCS subgroups were performed using the Pearson χ2test or the Fisher exact test. For the survival analyses, overall survival (OS) was defined as the time from the date of diagnosis to death for which uLMS was the primary or underlying cause. Survival was estimated using the Kaplan–Meier product-limit method, and differences were tested for statistical significance using the log-rank test. Cox proportional hazards regression models were used to identify the prognostic factor [HR and 95% confidence intervals (CI)]. Two-sided P values less than 0.05 were considered to be statistically significant. All analyses were performed using the SPSS Statistics20.0 software.