PDCD1 and pancreatic intraductal papillary-mucinous neoplasm: In this study, the positive rate for PD-1 expression on peripheral CD8+ T lymphocytes was 5% (1/20) in healthy donors, 27.5% (11/40) in IPMN patients, and 76.47% (52/68) in PDAC patients (using the median as the cut-off).