Cases of “pancreatic ductal adenocarcinoma (PDAC) concomitant with intraductal papillary mucinous neoplasm” (IPMN) have multiple PDAC lesions more frequently than cases of “PDAC without IPMN”. However, the mechanism of carcinogenesis in this former disease category remains unknown. The main objective of this work was thus to investigate the effects of chronic inflammation on carcinogenesis in PDAC cases. We selected 31 “PDAC concomitant with IPMN” patients and 58 “PDAC without IPMN” patients and pathologically evaluated their background pancreatic parenchyma. Fibrosis and inflammation scores of background pancreas were higher in “PDAC concomitant with IPMN” than in “PDAC without IPMN” (P < 0.0001 and P < 0.0001, respectively), whereas the fatty infiltration score of background pancreas was high in “PDAC without IPMN” (P = 0.0024). Immunohistochemically, the expression of 8-hydroxy-2′-deoxyguanosine (8-OHDG), an oxidative stress marker, in the background pancreas was high in “PDAC concomitant with IPMN” compared with that in “PDAC without IPMN” (P < 0.0001). Chronic inflammation activates oxidative stress in tissue throughout the pancreas and probably confers susceptibility to tumorigenesis in “PDAC concomitant with IPMN”.
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