Clinical strategies for differentiating autoimmune pancreatitis from pancreatic malignancy to avoid unnecessary surgical resection.

Objective: The study aimed to determine a practical strategy for differentiating between autoimmune pancreatitis (AIP) and pancreatic malignancy in order to avoid unnecessary surgical resection.

Methods: Altogether, 19 patients with AIP or other pancreatic diseases underwent routine examinations including liver function test and carbohydrate antigen 19-9, computed tomography and/or magnetic resonance imaging. Serum immunoglobulin G (IgG) and/or IgG4 was determined in patients with clinically suspected or pathologically proven AIP. Patients with suspected AIP either received diagnostic steroid therapy or laparotomy (if malignant tumors could not be excluded). Surgery was not performed in patients with a definite diagnosis of AIP by fast intraoperative frozen biopsy. Those with confirmed AIP received steroid treatment.

Results: In total, 15 cases were finally confirmed as AIP with eight diagnosed preoperatively, five confirmed by surgical pathology (preoperatively misdiagnosed) and two by intraoperative biopsy. Of these 15 patients with AIP and one without AIP, 14 had elevated serum γ-globulin levels. It was proven by subsequent antibody tests that serum IgG or IgG4 were simultaneously increased.

Conclusions: Elevated serum γ-globulin level can be used as a preoperative sentinel indicator for differentiating between IgG4-related AIP and pancreatic malignancy. Serum IgG or IgG4 tests should be further performed in those with elevated serum γ-globulin level, which helps to identify AIP in order to avoid unnecessary operation.