title: Autoimmune pancreatitis (AIP) type 1 and type 2: an international consensus study on histopathologic diagnostic criteria.
abstract: OBJECTIVE
  To develop and validate histologic diagnostic criteria for autoimmune pancreatitis (AIP) and its types.
  
  
  METHODS
  Thirteen pathologists participated in this 2-phase study to develop diagnostic criteria for AIP types 1 and 2 (phase 1) and validate them (phase 2). A virtual library of 40 resected pancreata with AIP and other forms of chronic pancreatitis (CP) was constructed. Readers reviewed the slides online and filled out a questionnaire for histopathologic findings and diagnosis.
  
  
  RESULTS
  Diagnostic criteria for AIP and its types were proposed according to the results from the top 5 reviewers in phase 1. The interobserver agreement was significantly improved in phase 2 by applying the proposed diagnostic criteria. Features distinguishing AIP from alcoholic and obstructive forms of CP were periductal lymphoplasmacytic infiltrate, inflamed cellular stroma with storiform fibrosis, obliterative phlebitis, and granulocytic epithelial lesions. Although there was overlap, 2 types of AIP were recognized. Type 1 had dense lymphoplasmacytic infiltrate with storiform fibrosis and obliterative phlebitis, whereas type 2 was distinguished from type 1 by the presence of granulocytic epithelial lesions.
  
  
  CONCLUSIONS
  Autoimmune pancreatitis can be distinguished from other forms of CP with substantial interobserver agreement. The 2 types of AIP can be distinguished by the proposed consensus histopathologic diagnostic criteria.
authors: Department of Laboratory and Anatomic Pathology, Mayo Clinic, Rochester, MN 55905, USA. zhang.lizhi@mayo.edu
authors: Lizhi
authors: L
authors: Zhang
authors: Suresh
authors: S
authors: Chari
authors: Thomas C
authors: TC
authors: Smyrk
authors: Vikram
authors: V
authors: Deshpande
authors: Günter
authors: G
authors: Klöppel
authors: Motohiro
authors: M
authors: Kojima
authors: Xiuli
authors: X
authors: Liu
authors: Daniel S
authors: DS
authors: Longnecker
authors: Mari
authors: M
authors: Mino-Kenudson
authors: Kenji
authors: K
authors: Notohara
authors: Manuel
authors: M
authors: Rodriguez-Justo
authors: Amitabh
authors: A
authors: Srivastava
authors: Giuseppe
authors: G
authors: Zamboni
authors: Yoh
authors: Y
authors: Zen
mesh_terms: D001327:Autoimmune Diseases / Q000145:classification / Q000175:diagnosis* / Q000276:immunology; D032921:Consensus; D003937:Diagnosis, Differential; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis; D007150:Immunohistochemistry; D007391:International Cooperation; D010179:Pancreas / Q000276:immunology / Q000473:pathology*; D010195:Pancreatitis / Q000145:classification / Q000175:diagnosis* / Q000276:immunology; D050500:Pancreatitis, Chronic / Q000175:diagnosis / Q000276:immunology; D010338:Pathology, Clinical / Q000379:methods*; D010950:Plasma Cells / Q000276:immunology / Q000473:pathology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D007074:Immunoglobulin G