A possible explanation is that tumor cells expressing PD-L1 trigger the immune response in both dMMR and pMMR colon tumors, but depending on the MMR status, there may be differences in the intensity of CTLs migrating to the tumor tissue, the expression of PD-L1 on immune cell infiltrates, and the extent of PD-1 upregulation. Here, PDCD1 is linked to colonic neoplasm.