Utility of 18 F-FDG PET/CT for Differentiation of Autoimmune Pancreatitis With Atypical Pancreatic Imaging Findings From Pancreatic Cancer

OBJECTIVE: This study was conducted to evaluate the clinical usefulness of PET/CT in differentiating autoimmune pancreatitis from pancreatic cancer. MATERIALS AND METHODS: To differentiate autoimmune pancreatitis from pancreatic cancer, we analyzed the cases of 17 patients with autoimmune pancreatitis and atypical pancreatic imaging findings who underwent integrated PET/CT. The PET/CT findings on the 17 patients with autoimmune pancreatitis were compared with those of 151 patients with pancreatic cancer. RESULTS: Fluorine-18 FDG uptake by the pancreas was found in all patients with autoimmune pancreatitis and in 82% (124/151) of patients with pancreatic cancer. Diffuse uptake by the pancreas was significantly more frequent in patients with autoimmune pancreatitis (53% vs 3%, p < 0.001). FDG uptake by the salivary glands and kidneys was seen only in patients with autoimmune pancreatitis, the former reaching statistical significance (p = 0.003). Follow-up PET/CT after steroid therapy was performed for eight patients with autoimmune pancreatitis. After steroid therapy, none of the patients had intense FDG uptake by the pancreas or extrapancreatic organs. CONCLUSION: In difficult cases, at PET/CT the presence of diffuse uptake of FDG by the pancreas or concomitant extrapancreatic uptake by the salivary glands can be used to aid in differentiation of autoimmune pancreatitis and pancreatic cancer.