Significant infiltration of the major duodenal papilla by FOXP3(+) lymphocytes (≥ 14/HPF) was recognized in 18 of the 32 patients with AIP (sensitivity 56.3%, specificity 100%, accuracy 77.4%).
The K-ras mutation was detected in the fibroinflammatory pancreas, the bile duct, and the gallbladder, with abundant infiltrating IgG4-positive plasma and Foxp3-positive cells of patients with AIP with elevated serum IgG4 levels.