*3.5. Immune Checkpoint Molecules*

The expression of PD-L1 was observed on cell membrane and in the cytoplasm of tumor cells (Figure 4). The endothelial cells were also occasionally immunopositive for PD-L1. In the CS (+) group, the PD-L1 score was 2 or 3 in eight patients, and 0 or 1 in nine of the 17 patients. In contrast, in the CS (−) group, the PD-L1 score was 2 or 3 in one patient, and 0 or 2 in nine of the 10 patients. The score tended to be higher in the CS (+) group than in the CS (−) group, but the difference is not statistically significant (*p* = 0.050; Figure 4). There were no significant differences in PD-1 (+) cells between the two groups (0.61 vs. 0.50, *p* = 0.39).
