Histopathologic characteristics of autoimmune pancreatitis based on comparison with chronic pancreatitis.

OBJECTIVES: To clarify the histopathologic characteristics of autoimmune pancreatitis (AIP), based on comparison with both chronic alcoholic pancreatitis (CAP) and chronic obstructive pancreatitis (COP). METHODS: Three AIP patients, 17 CAP patients, and 19 COP patients were studied histopathologically. RESULTS: There was a dense lymphoplasmacytic infiltrate, especially within and around the pancreatic ducts, and fibrosis associated with AIP, while there was fibrosis accompanied by mild inflammatory infiltration in both CAP and COP. Inter- and intralobular fibrosis admixed with acinar atrophy was observed in both AIP and COP, while interlobular fibrosis combined with a "cirrhosis-like" appearance was found in CAP. Obliterative phlebitis was found in AIP, while thrombosis of the splenic vein was exhibited in CAP. CONCLUSION: Autoimmune pancreatitis was histologically characterized by dense lymphoplasmacytic infiltrate combined with fibrosis, acinar atrophy, obliterative phlebitis, and ductal involvement.