Clinicopathological analysis of 12 patients with autoimmune pancreatitis.

Autoimmune pancreatitis (AIP) is a rare type of chronic pancreatitis that is often misdiagnosed as pancreatic cancer (PaC). This study was undertaken to investigate the clinicopathological characteristics of AIP, in order to improve the diagnosis and treatment of the disease. Among the 271 patients with PaC who underwent pancreatoduodenectomy between January 2003 and December 2012 at the Sun Yat-Sen Memorial Hospital, chronic pancreatitis was identified and tissue samples obtained from 16 patients. The clinicopathological and imaging characteristics of 16 of the patients with chronic pancreatitis were analyzed retrospectively. The expression of immunoglobulin G4 (IgG4) in the pancreas tissue was detected by immunohistochemistry. Immunohistochemistry showed that IgG4 was highly expressed in 12 out of the 16 patients, and those 12 patients were diagnosed with AIP. Among those 12 patients, 6 presented with emaciation and 7 with jaundice and abdominal pain, respectively. Among the 16 included patients, 12 had an elevated level of serum γ-glutamyltransferase and 9 had an elevated level of serum carbohydrate antigen 19-9. The imaging features were as follows: Pancreatic enlargement in 11 patients (particularly pancreatic head enlargement), pancreatic miniature in 1, 'sausage-like' pancreatic changes in 4 and 'halo' sign pancreatic changes in 5. Massive plasma cell infiltration (11/12) and parenchymal fibrosis (8/12) were observed in the pancreatic tissues through pathology. These results suggest that combining imaging with IgG4 expression for the purpose of diagnosis can enhance the preoperative diagnostic value and reduce the rate of AIP misdiagnosis.