Giuffrida P, et al. - The intent of this study was to evaluate programmed cell death ligand 1 (PD-L1) and PD-1 expression in non-hereditary, non-ampullary small bowel adenocarcinomas (SBAs), associated with celiac disease (CeD), Crohn’s disease (CrD), or sporadic, recruited through the Small Bowel Cancer Italian Consortium. PD-L1 and PD-1 were measured by immunohistochemistry in a series of 121 surgically resected SBAs, including 34 CeD-SBAs, 49 CrD-SBAs, and 38 sporadic SBAs. PD-L1 and PD-1 expression were associated with several clinicopathological features, such as the etiology, microsatellite instability status, and tumor-infiltrating lymphocyte (TIL) density. In comparison with sporadic SBAs, this study shows an enhanced proportion of PD-L1+ cases in both CeD-SBAs and CrD-SBAs. The results of this study displayed that identification of a subset of PD-L1+ microsatellite stable SBAs supports the requirement to determine additional biomarkers of response to immune checkpoint inhibitors along with MSI-H.