The purpose of the present retrospective study was to evaluate correlations between serum sPD-L1 levels and clinicopathological parameters and to elucidate whether sPD-L1 levels and PD-L1 expressed on tumor cells can be used to distinguish the malignant phenotype in soft tissue tumor patients and to predict recurrence, metastasis, or prognosis in STS patients. The gene discussed is SPDL1; the disease is soft tissue neoplasm.