Differentiation of autoimmune pancreatitis from suspected pancreatic cancer by fluorine-18 fluorodeoxyglucose positron emission tomography

Abstract

Purposes: Fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) has been widely used for the diagnosis of pancreatic cancer. Because autoimmune pancreatitis is easily misdiagnosed as pancreatic cancer and can be tested for by FDG-PET analysis based on the presence of suspected pancreatic cancer, we attempted to clarify the differences in FDG-PET findings between the two conditions. Methods: We compared the FDG-PET findings between 15 patients with autoimmune pancreatitis and 26 patients with pancreatic cancer. The findings were evaluated visually or semiquantitatively using the maximum standardized uptake value and the accumulation pattern of FDG. Results: FDG uptake was found in all 15 patients with autoimmune pancreatitis, whereas it was found in 19 of 26 patients (73.1%) with pancreatic cancer. The accumulation pattern of nodular shape was frequently seen in pancreatic cancer with significance, whereas a longitudinal shape indicated the existence of autoimmune pancreatitis. Heterogeneous accumulation was found in almost all cases of autoimmune pancreatitis, whereas homogeneous accumulation was found in pancreatic cancer. Most cases of pancreatic cancer showed solitary localization with significant difference, whereas multiple localizations in the pancreas favored the existence of autoimmune pancreatitis. FDG uptakes in the hilar lymph node were more frequently seen in autoimmune pancreatitis than in pancreatic cancer with significance, and those in the lachrymal gland, salivary gland, biliary duct, retroperitoneal space, and prostate were only seen in autoimmune pancreatitis. Conclusions: FDG-PET provides a useful tool for differentiating autoimmune pancreatitis from suspected pancreatic cancer, if its accumulation pattern and extra-pancreatic involvements are considered. IgG4 measurement and other current image tests will confirm further diagnosis.

Amendment of the Japanese Consensus Guidelines for Autoimmune Pancreatitis, 2013 I. Concept and diagnosis of autoimmune pancreatitis

“…In these cases, the accumulation corresponds to the prominent inflammatory cell infiltration areas [63][64][65][66]. FDG also accumulates in extra-pancreatic lesions such as in the salivary gland, a wide range of lymph node lesions, retroperitoneal fibrosis, and the prostate gland [67][68][69]. Accumulated FDG in pancreatic or extra-pancreatic areas disappears quickly after steroid treatment [66].…”

Amendment of the Japanese Consensus Guidelines for Autoimmune Pancreatitis, 2013 II. Extrapancreatic lesions, differential diagnosis

“…In AIP, the pancreatic distribution is diffuse, with signals at multiple sites, while the signal is restricted to a solitary site in pancreatic cancer, [32,103]. FDG accumulation in AIP also appears at extrapancreatic sites, such as the lachrymal and salivary glands or the hilar lymph node.…”

“…FDG accumulation in AIP also appears at extrapancreatic sites, such as the lachrymal and salivary glands or the hilar lymph node. These features are useful for distinguishing between AIP and pancreatic cancer [32,103,104]. Another useful differentiating feature in AIP is a rapid decrease in FDG accumulation after corticosteroid therapy [104,105].…”

“…These characteristics indicate a common pathophysiological background, which suggests the presence of a systemic a b IgG4-related disease [30]. The lesions are typically detected with imaging (CT, MRI, gallium scintigraphy, FDG-PET) [2,31,32] and blood tests (hormone assays), but results should be confirmed with histological findings. Extrapancreatic lesions sometimes mimic or are misdiagnosed as primary lesions in the corresponding organ.…”

Autoimmune pancreatitis in Japan: overview and perspective

“…Although [ 18 F]fluorodeoxyglucose positron emission tomography (FDG-PET) is unable to differentiate AIP from pancreatic cancer, because the latter also takes up FDG, showing a high SUVmax [45], this imaging modality is very useful in understanding the distribution of involved extrapancreatic organs such as salivary glands, pulmonary hilar lymph nodes, retroperitoneal fibrosis and prostate gland [46,47]. The accumulation of FDG in extrapancreatic lesions also disappears promptly in response to steroid treatment ( Fig.…”