Autoimmune pancreatitis: Pancreatic manifestation of IgG4-related disease

Autoimmune pancreatitis (AIP) is a unique inflammatory disorder of the pancreas. Two histological types are recognized: lymphoplasmacytic sclerosing pancreatitis and idiopathic duct-centric chronic pancreatitis, with the former representing the pancreatic manifestation of IgG4-related disease. Presented here is a 64-year-old man who was incidentally found to have a mass in the pancreatic tail. The resected specimen revealed typical histological features of lymphoplasmacytic sclerosing pancreatitis, consisting of storiform fibrosis, obliterative phlebitis, and characteristic lobular and ductal inflammation. IgG4-positive plasma cells were numerous, and his serum IgG4 level was elevated (436 mg/dL). He also had systemic lesions, such as hypophysitis, bilateral eyelid lesions and bilateral pleural thickening, that most likely represented IgG4-related disease. Sometimes the distinction of AIP from cancer is clinically difficult, especially in cases with a localized lesion and/or without serological abnormalities; thus, pancreatic resection may be carried out. Pancreas biopsy is attracting attention as a diagnostic tool, and pathologists may play an important role in diagnosing AIP in the future.