We examined the expression of PD-1 and CD8 in tumour-infiltrating lymphocytes by double immunofluorescence staining (IF) of 94 pairs of resection specimens (tumour tissues and matched adjacent non-tumour tissues) from PDAC patients (34 female and 60 male patients with a median age of 65 years; age range, 43–88 years). The gene discussed is PDCD1; the disease is neoplasm.