SPDL1 and neoplasm: The distribution of PD-L1-postive tumor cells showed a modest association with serum levels of sPD-L1 (r = 0.299, P = 0.031, Fig. 2b) whereas the percentage of PD-L1-postive immune cells including macrophages did not correlate with serum sPD-L1 levels (Fig. 2c).