As shown in Table 1, PD-1 expression on tumour-infiltrating CD8+ T lymphocytes in PDAC was significantly correlated with clinical stage (χ2 = 6.136, P = 0.013), N classification (χ2 = 7.575, P = 0.023), and M classification (χ2 = 17.375, P < 0.001). Here, PDCD1 is linked to neoplasm.