A representative case of PD-L1 inhibitor presenting the discrepancy between tumor PD-L1 and serum exosomal PD-L1 level is shown in Fig. 6; this patient demonstrated low tumor PD-L1 (TPS 3%) and high serum exosomal PD-L1 (240 pg/mL; patient 5 in Supplementary Table S1). Here, CD274 is linked to neoplasm.