The differentiation of autoimmune pancreatitis and pancreatic cancer using imaging findings.

Objective: Differentiation of autoimmune pancreatitis (AIP) and pancreatic cancer (PC) is important to avoid unnecessary surgery. The aim of this study was to compare various image findings and facilitate the differentiation of these two diseases.

Methods: The radiological features of 36 AIP patients and 36 patients with resected PC diagnosed at Samsung Medical Center from January 1991 to October 2010, were compared.

Results: Regarding CT/MRI findings, diffuse pancreas enlargement, capsule-like rim and delayed homogenous enhancement, were significantly more frequent in AIP. For cholangiopancreatography findings, main pancreatic duct (MPD) narrowing by ≥1/3 of the pancreatic length, skipped lesions of the MPD, the presence of side branches at the narrowed MPD portion, and smooth and straight intrapancreatic common bile duct stenosis were significantly more frequent in AIP. However, according to FDG-PET findings, SUVmax, uptake shape and pattern, and uptake by extrapancreatic lesions were not significantly different for AIP and PC.

Conclusions: Diffuse pancreas enlargement, a capsule-like rim, delayed homogenous enhancement, MPD narrowing of ≥1/3 of the pancreatic length, skipped lesions and the presence of side branches at the narrow MPD portion were found to have high specificity for AIP. These findings have great power to differentiate AIP and PC.