title: A diagnostic strategy to distinguish autoimmune pancreatitis from pancreatic cancer.
abstract: OBJECTIVE
  Autoimmune pancreatitis (AIP) and pancreatic cancer (PaC) have similar presentations; a diagnostic strategy is needed to distinguish the 2 diseases.
  
  
  METHODS
  We compared computed tomography images (for pancreas and other organ involvement), serum IgG4 levels, histology data, and the response to steroids between patients with AIP (n = 48) and those with PaC (n = 100).
  
  
  RESULTS
  Pancreatic imaging findings stratified patients into 3 groups. Group 1 was highly suggestive of AIP, with diffuse pancreatic enlargement without group 3 features (n = 25, 100% AIP). Group 2 was indeterminate, with normal-sized pancreas or focal pancreatic enlargement without group 3 features (n = 20, 75% AIP). Group 3 was highly suggestive of PaC, with presence of >1 low-density mass, pancreatic duct cutoff, or upstream pancreatic atrophy (n = 103, 92% PaC). Although all patients in group 1 had AIP, only 20 of the 25 patients had increased serum IgG4 levels and/or other organ involvement. Of the patients in groups 2 and 3 who did not have cancer, all those with serum IgG4 levels >2-fold the upper limit of normal or a combination of increased serum IgG4 levels and other organ involvement (n = 15) had AIP. In AIP subjects without supportive serologic evidence or other organ involvement (n = 14), diagnosis required pancreatic core biopsy (n = 7), steroid trial (n = 5), or resection (n = 2).
  
  
  CONCLUSIONS
  PaC can be distinguished from AIP by pancreatic imaging, measurement of serum IgG4 levels, and determination of other organ involvement. However, a pancreatic core biopsy, steroid trial, or surgery is required for diagnosis in approximately 30% of patients with AIP.
authors.affiliation: Miles and Shirley Fiterman Center for Digestive Diseases, Mayo Clinic College of Medicine, Rochester, Minnesota, USA. chari.suresh@mayo.edu
authors.forename: Suresh T
authors.initials: ST
authors.lastname: Chari
authors.forename: Naoki
authors.initials: N
authors.lastname: Takahashi
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Levy
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Smyrk
authors.forename: Jonathan E
authors.initials: JE
authors.lastname: Clain
authors.forename: Randall K
authors.initials: RK
authors.lastname: Pearson
authors.forename: Bret T
authors.initials: BT
authors.lastname: Petersen
authors.forename: Mark A
authors.initials: MA
authors.lastname: Topazian
authors.forename: Santhi S
authors.initials: SS
authors.lastname: Vege
mesh_terms: D000368:Aged; D000893:Anti-Inflammatory Agents / Q000627:therapeutic use; D001327:Autoimmune Diseases / Q000175:diagnosis*; D003937:Diagnosis, Differential; D005260:Female; D006651:Histocytochemistry; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D007074:Immunoglobulin G / Q000097:blood; D008297:Male; D008875:Middle Aged; D010179:Pancreas / Q000000981:diagnostic imaging / Q000473:pathology; D010190:Pancreatic Neoplasms / Q000175:diagnosis*; D010195:Pancreatitis / Q000175:diagnosis*; D011859:Radiography; D013256:Steroids / Q000627:therapeutic use; D014054:Tomography
chemical_list: D000893:Anti-Inflammatory Agents; D007074:Immunoglobulin G; D013256:Steroids