Type 1 autoimmune pancreatitis with main pancreatic duct dilatation and pancreatic cysts: A case report

Abstract

A 72-year-old man who was diagnosed with intraductal papillary mucinous carcinoma by EUS and EUS-FNA was referred to our hospital for surgery. Abdominal CT showed a well-defined hypovascular tumor in the pancreatic head and main pancreatic duct dilatation from the pancreatic head to the body. MRCP revealed dilatation and moniliform aspect of the pancreatic duct branches in the pancreatic head. After subtotal stomach-preserving pancreaticoduodenectomy, sectioning of the resected specimen revealed the whitish solid mass containing the small cysts. Histological examination showed infiltration and fibrosis of inflammatory cells mainly composed of IgG4-positive plasma cells around the cystic dilated pancreatic ducts. Storiform fibrosis and obliterative phlebitis were also observed. Intraductal papillary neoplasm was not detected in any epithelium of the pancreatic ducts. We defined it as type 1 autoimmune pancreatitis.