SPDL1 and metastatic malignant neoplasm in the lymph nodes: This study aimed to investigate the correlation of sPD-1 and sPD-L1 with clinical and pathological characteristics and lymph node metastasis by measuring their serum levels in patients who were operated for early-stage NSCLC and besides to compare preoperative serum sPD-1 and sPD-L1 levels with the post-resection values and with normal population.