[An IgG4-related pancreatitis mimicking an adenocarcinoma: A case report].

Type 1 auto-immune pancreatitis (type 1 AIP) is the pancreatic manifestation of IgG4-related systemic disease (IgG4-RD). This disease has recently been individualized and is characterized by elevated serum IgG4 levels and extrapancreatic lesions with common histologic characteristic: dense infiltration of lymphocytes, IgG4-positive plasma cells and storiforme fibrosis. Obliterative phlebitis is frequently detected. The pancreas is frequently involved in this disease. As approach to the pancreas for histological examination is generally difficult, AIP is diagnosed using a combination of clinical, serological, morphological and histopathological features. In pseudotumoral cases, AIP can be misdiagnosed as pancreatic cancer. Since AIP responds dramatically to steroid therapy, accurate diagnosis of AIP can avoid unnecessary laparotomy or pancreatic resection. We report here a case of a patient who underwent surgery for presumed pancreatic cancer. The final diagnosis was type 1 AIP.