Lee et al. showed that PD-L1 positivity in tumor cells and PD-1 positivity in tumor-infiltrating lymphocytes in mismatch-repair proficient colorectal cancer were only 2% and 13%, respectively, which are significantly lower than the positivity rates (18% and 50%) reported for mismatch-repair deficient colorectal cancer [12]. This evidence concerns the gene PDCD1 and colorectal cancer.