Association between autoimmune pancreatitis and malignancy.

Chronic inflammatory diseases are often associated with malignancy, and this phenomenon occurs even in the field of gastroenterology. For example, chronic pancreatitis has been reported to be highly associated with the occurrence of pancreatic cancer. However, the association between autoimmune pancreatitis (AIP) and pancreatic cancer is still an unsolved problem. As AIP is associated with immunoglobulin G4-related disease, which causes a variety of inflammatory and fibrotic lesions, the association between AIP and total malignancies is also a matter of interest. Here, we discuss the association between AIP and malignancy. As for the association between AIP and pancreatic cancer, there is no conclusive evidence, although several reports have suggested that the relative risk of pancreatic cancer is high in AIP. Concerning the association between AIP and total malignancies, there are two reports from Japan. Neither report supported the idea that chronic inflammation in AIP caused the increased risk of total malignancies. However, one report proposed the possibility that AIP might develop as a paraneoplastic syndrome in some patients because many cancers occurred within 1 year of AIP diagnosis, and thereby concluded that patients with AIP were at high risk of having various cancers. The paraneoplastic syndrome hypothesis should be tested in future studies.