Distinguishing autoimmune pancreatitis from pancreaticobiliary cancers: current strategy.

OBJECTIVE: A review of the literature to identify current modalities for the diagnosis of autoimmune pancreatitis (AIP) with the objective of establishing a strategy to distinguish it from pancreaticobiliary cancers.
BACKGROUND: Pancreatic and biliary manifestations of AIP mimic pancreaticobiliary cancers. Misdiagnosis of AIP can result in major surgery for a steroid-responsive disease.
METHODS: A review of the literature was performed to identify recent advances in the diagnosis of AIP and evaluate outcomes with various diagnostic strategies to minimize operative intervention for an autoimmune disease.
RESULTS: Diagnostic criteria for AIP are based on histology, imaging, serology, extrapancreatic organ involvement, and response to steroid therapy. The most commonly involved extrapancreatic sites are bile duct, kidney, and retroperitoneum. The Mayo Clinic diagnostic strategy utilizes core biopsy of the pancreas and the Japanese strategy depends on a characteristic pancreatogram. The rate of operative intervention was similar with both strategies and none of the patients with cancer received steroid therapy. Immunoglobulin G subtype 4 (IgG4)-associated cholangitis mimics cholangiocarcinoma and presence of more than 10 IgG4-positive plasma cells/high power field on endoscopic biopsy of the bile duct was diagnostic for AIP in 88% patients. Biliary complications and early relapse are common after surgical resection and immunomodulatory drugs can maintain long-term remission.
CONCLUSION: Criteria based on histology, imaging, endoscopy, serology, extrapancreatic organ involvement, and response to steroid therapy improve the diagnostic yield for AIP. Application of diagnostic and therapeutic protocols by a multidisciplinary team will optimize outcomes with a decline in the rate of operative intervention for AIP, a steroid-responsive disease with propensity for relapse.