title: Magnetic resonance imaging findings of the mass-forming type of autoimmune pancreatitis: comparison with pancreatic adenocarcinoma.
abstract: OBJECTIVE
  To determine the characteristic magnetic resonance imaging (MRI) features of mass-forming autoimmune pancreatitis (AIP), which allow its differentiation from pancreatic adenocarcinoma (PAC).
  
  
  METHODS
  MR images of 37 patients with either pathologically proven, mass-forming AIPs (n = 9) or PACs (n = 28) were retrospectively reviewed. The pancreatic MR protocol included unenhanced images, contrast-enhanced dynamic images, diffusion-weighted imaging (DWI), and MR-cholangiopancreatography (MRCP). Two reviewers analyzed the MR images regarding the number, location, morphologic features, and enhancement degree and pattern of the lesions as well as secondary changes of the pancreatic parenchyma, the biliary and pancreatic ducts. The size and apparent diffusion coefficient (ADC) values of the lesions were measured.
  
  
  RESULTS
  Although sensitivities were low (28.6%-44.4%), specificities of multiplicity, capsule-like rim enhancement, and skipped stricture of the biliary or pancreatic duct in mass-forming AIP were high (100%). Sensitivities and specificities of irregular or geographic shape, delayed enhancement, and a low ADC value <1.26 × 10(-3) mm(2) /s in mass-forming AIP were favorable (71.4%-83.3% and 78.5%-89.3%).
  
  
  CONCLUSIONS
  Although to differentiate mass-forming AIP from pancreatic cancer is difficult, the combination of MRI findings including contrast-enhanced dynamic images, MRCP, and DWI can be a help.
authors.affiliation: Department of Radiology and Institute of Radiation Medicine, Seoul National University Hospital, Seoul, Korea.
authors.forename: Bo Yun
authors.initials: BY
authors.lastname: Hur
authors.forename: Jeong Min
authors.initials: JM
authors.lastname: Lee
authors.forename: Jeong Eun
authors.initials: JE
authors.lastname: Lee
authors.forename: Jae Yong
authors.initials: JY
authors.lastname: Park
authors.forename: Soo Jin
authors.initials: SJ
authors.lastname: Kim
authors.forename: Ijin
authors.initials: I
authors.lastname: Joo
authors.forename: Cheong Il
authors.initials: CI
authors.lastname: Shin
authors.forename: Jee Hyun
authors.initials: JH
authors.lastname: Baek
authors.forename: Jung Hoon
authors.initials: JH
authors.lastname: Kim
authors.forename: Joon Koo
authors.initials: JK
authors.lastname: Han
authors.forename: Byung Ihn
authors.initials: BI
authors.lastname: Choi
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology*; D000328:Adult; D000368:Aged; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010179:Pancreas / Q000473:pathology*; D010190:Pancreatic Neoplasms / Q000473:pathology*; D010195:Pancreatitis / Q000473:pathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity