A Nondilated Main Pancreatic Duct Predicts Type 2 Autoimmune Pancreatitis: Comparative Study of Resected Pancreatic Head Masses

Background: Chronic pancreatitis (CP), pancreatic cancer (PCa), and autoimmune pancreatitis (AIP) often present as a pancreatic mass. Accurate diagnosis is not always possible; up to 8% of surgical procedures are performed in benign pancreatic masses presumed to be malignant. Objectives: We aimed to compare clinical and imaging characteristics of resected focal type 2 AIP, CP, and PCa and identify factors that could improve preoperative differential diagnosis. Methods: Charts from patients that underwent pancreatic resection under suspicion of PCa between 2000 and 2014 were reviewed. Clinical and imaging data were recorded. Subjects were grouped as type 2 AIP, CP, and PCa. Results: We included 79 cases; 41 men, mean age of 57.3 years/old +/- 15.6 SD. Pathology report was type 2 AIP (20%), CP (10%), and PCa (70%). According to international consensus criteria for AIP 11 cases were deemed probable type 2 and 5 as unspecific pancreatic mass. A nondilated main pancreatic duct (MPD) was associated with AIP (OR 9.3; 95% CI 3.05-28.7), p < 0.001; obstructive jaundice (OR 28.5; 95% CI 8.18-79.5); and a dilated MPD (OR 5.21; 95% CI 1.9-14.6) suggested malignancy. Conclusions: In the setting of undetermined pancreatic focal mass, a nondilated MPD suggests the diagnosis of type 2 AIP.