Another potential reason for the lack of observed differences in circulating sPD-L1 level among histologic types is that sPD-1 and sPD-L1 are not exclusive to tumour cells [27] and are released by diverse cell populations through different mechanisms, including intrinsic splicing [13], [28] and the cleavage of membrane-bound counterparts [11]. This evidence concerns the gene SPDL1 and neoplasm.