PDCD1 and cancer: PD-1 expression in cancer cells showed a borderline positive correlation with CD3+ TILs/mm2 (p = 0.05, Mann-Whitney), but not with PD-1+, PD-L1+, CD4+, or CD8+ TILs, and PD-L1 expression in cancer was not significantly associated with TILs at all (p > 0.05 each).