Localized autoimmune pancreatitis mimicking pancreatic cancer: Case report and literature review

Abstract

Autoimmune pancreatitis (AP) is a rare autoimmune pancreatic manifestation of systemic immunoglobulin G4 (IgG4)-related sclerosing disease. Distinguishing between AP and pancreatic cancer is crucial because the clinical courses, treatments, and prognoses of these two disease entities are quite different. We herein report a case involving a 52-year-old man with subacute epigastralgia who visited our hospital for evaluation of a suspicious pancreatic mass found during esophagogastroduodenoscopy. Enhanced computed tomography (CT) revealed an enlarged lesion in the pancreatic head with encasement of hepatic vessels. The lesion also exhibited increased 18F-fluorodeoxyglucose accumulation on positron emission tomography/CT imaging, which was highly suggestive of pancreatic cancer. After open biopsy, morphologic examination showed an inflammatory infiltrate in the pancreas, which was compatible with chronic sclerotic pancreatitis. Further laboratory tests revealed an elevated serum IgG4 level, and the diagnosis of sclerotic pancreatitis was then confirmed. After corticosteroid treatment, the pancreatic lesion showed shrinkage on follow-up CT, and the serum IgG4 titer decreased to the normal range. This case suggests that clinicians should be familiar with the clinical presentations and diagnostic criteria of AP versus pancreatic cancer. An awareness of the differences between these diseases may avoid misdiagnosis and unnecessary surgical intervention.

Acute Findings on FDG PET/CT: Key Imaging Features and How to Differentiate Them from Malignancy

“…Visceral organs can also demonstrate increased FDG uptake. For example, acute pancreatitis shows increased FDG uptake [ 39 – 41 ]. CT appearance, FDG uptake pattern, and clinical symptoms are key.…”

Untypical autoimmune pancreatitis and pancreatic cancer: differential diagnosis experiences extracted from misdiagnose of two cases

“…However, postoperative histologic analysis of the pancreatic head revealed moderate lymphoplasmacytic infiltration with obliterative venulitis and stromal fibrosis. Immunohistochemically, abundant IgG4-positive plasma cells (> 20/hpf and IgG4+/IgG+ plasma cell ratio > 40%) were observed infiltrating the head of the pancreas, consistent with AIP [3]. Further examination showed all the serum immune antibody including IgG4 were within normal range except slightly elevation of IgM and AMA (Table 2).…”

“…Adjacent low-grade FDG-avid lymph nodes with a maximum standardized uptake value of 3.0 were also noted. No FDG-avid lesions were present in the bilateral salivary glands, retroperitoneal spaces, orbiliary tracts [3]. In all, these findings were highly suggestive of obstructive jaundice due to a malignant pancreatic tumor with no distant metastasis.…”

“…(1): In the patients with typical AIP, US, CT and MRI were less likely to find a discrete pancreatic mass and more likely to find a diffusely enlarged pathological pancreatic head in a swollen pancreas [7]. ERCP and MRCP generally shows fairly distinctive irregular narrowing of the dilated main pancreatic duct [3]. However, focal form of AIP in the present study and PC share many features, including sudden jaundice, elevation of tumor markers, and imaging manifestations of focal mass in the pancreas, “double-duct sign” representing stricture in both the biliary and pancreatic ducts, and angiographic abnormalities, which make the discrimination very challenging.…”

“…The major limitations of the technique are operator dependence and a limited field of visualization for detecting metastatic spread to the liver and peritoneum. Furthermore, there is a high rate of false-negative results as seen in a previous study, especially in patients who have the smallest lesions and/or in the presence of chronic pancreatitis, due to the inadequate sample provided (even by core biopsies) [3, 14]. In addition, as an autoimmune disease, the dynamic interaction between endogenous and exogenous factors and the immune system play a key role in the pathogenesis and propagation of inflammation as well as healing process, which may make preoperative histological test miss the histological and immunohistochemical characteristic of AIP.…”