title: Clinical and imaging features of autoimmune pancreatitis with focal pancreatic swelling or mass formation: comparison with so-called tumor-forming pancreatitis and pancreatic carcinoma.
abstract: OBJECTIVE
  Autoimmune pancreatitis (AIP) with a mass formation or swollen pancreas located in one or two segments of the gland (focal type AIP) has been reported. The aims of this study were to elucidate the relationship of the disease entity between this focal variant and so-called tumor-forming pancreatitis (TFP) and to describe the clinical and imaging features discriminating focal AIP from pancreatic carcinoma (Pca).
  
  
  METHODS
  The clinical, radiologic, and pathologic profiles of nine patients with focal AIP were reviewed retrospectively and compared with those of 11 patients with alcohol-induced TFP and 80 patients with Pca.
  
  
  RESULTS
  The patients with focal AIP were predominantly older (mean age 64.7 +/- 13.6 yr, range 28-78 yr), male, and presenting with obstructive jaundice or focal pancreatic enlargement accompanied by mild abdominal symptoms. In comparison, the patients with alcohol-induced TFP who were mostly middle-aged (mean age 50.1 +/- 7.95 yr, range 39-62 yr), male, and often had attacks of pancreatitis associated with findings of CT scans showing pseudocysts or peripancreatic effusion. Focal AIP usually demonstrated no abnormalities on pancreatograms downstream from the stricture or obstruction and often presented few contrast-filled side branches in the area of main pancreatic duct (MPD) stenosis. These characteristics were similar to the imaging features of Pca. Significant factors differentiating focal AIP from Pca were lower serum levels of CA19-9, homogeneous delayed enhancement evident in dynamic CT scans, and ERCP findings exhibiting a longer stenosed MPD and a thinner MPD upstream from the stricture.
  
  
  CONCLUSIONS
  Focal AIP is associated with clinical and radiologic features that are different from those of alcohol-induced TFP. In TFP there are two causative factors, namely, AIP and alcohol-induced chronic pancreatitis. Differential diagnosis of focal AIP from Pca seems to be possible in many cases by evaluating imaging findings such as dynamic CT and ERCP, although focal AIP sometimes shows clinical and radiologic features similar to those of Pca.
authors.affiliation: Department of Gastroenterology, Saiseikai Kanazawa Hospital, Kanazawa, Japan.
authors.forename: Tokio
authors.initials: T
authors.lastname: Wakabayashi
authors.forename: Yukimitsu
authors.initials: Y
authors.lastname: Kawaura
authors.forename: Yoshitake
authors.initials: Y
authors.lastname: Satomura
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Watanabe
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Motoo
authors.forename: Takashi
authors.initials: T
authors.lastname: Okai
authors.forename: Norio
authors.initials: N
authors.lastname: Sawabu
mesh_terms: D000328:Adult; D000368:Aged; D001327:Autoimmune Diseases / Q000175:diagnosis*; D016009:Chi-Square Distribution; D003937:Diagnosis, Differential; D003952:Diagnostic Imaging; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010186:Pancreatic Function Tests; D010190:Pancreatic Neoplasms / Q000175:diagnosis*; D010195:Pancreatitis / Q000175:diagnosis*; D012189:Retrospective Studies