Autoimmune pancreatitis type 1 (AIP-1) is an IgG4-related disease. Which diagnostic histological feature is most specific for AIP-1?

• A Islet cell loss with lymphocytic infiltration only
• B Acinar atrophy with mucin-filled ductal cysts
• C Neutrophilic infiltrate within pancreatic ducts (neutrophilic epithelial lesions)
• D Periductal lymphoplasmacytic inflammation with storiform fibrosis and obliterative phlebitis ✓

Explanation

AIP type 1 (IgG4-related pancreatitis) shows the classic triad of periductal lymphoplasmacytic inflammation with >10 IgG4+ plasma cells/HPF, storiform (whorling) fibrosis obliterating the normal lobular architecture, and obliterative phlebitis (lymphoplasmacytic inflammation destroying venous walls). These histological features (LPSP — lymphoplasmacytic sclerosing pancreatitis) are common to all IgG4-related diseases. AIP type 2 (IDCP — idiopathic duct-centric pancreatitis) shows neutrophilic epithelial lesions in ducts (GEL — granulocytic epithelial lesions) and is associated with IBD.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.