[595] Does IgG4 Immunostain on Endoscopic Biliary and Ampullary Biopsies Predict the Likelihood of Autoimmune Pancreatitis?

CE Aguilar, JC Bucobo, B Boulay, SK Lo, D Dhall, D Frishberg, M Kahn, R Mertens, J Zhai, HL Wang. Cedars-Sinai Medical Center, Los Angeles, CA

Background: Autoimmune pancreatitis (AIP) is characterized by elevation of serum IgG4 level, increased numbers of IgG4-positive plasma cells in tissue, and responsiveness to steroid therapy. The diagnosis can be challenging, and it can be difficult to distinguish AIP from pancreatic neoplasms clinically and radiographically. The current study was undertaken to determine whether IgG4 immunostains performed on endoscopic biliary and ampullary biopsies could help establish the diagnosis of AIP.
Design: Endoscopic biliary and ampullary biopsies from 40 patients with clinical differential diagnosis including AIP were included in this study. All biopsies were immunohistochemically stained for IgG4 at the time of endoscopic examination using a monoclonal antibody. The number of IgG4-positive plasma cells in each case was determined by averaging the numbers identified in 3 high power fields (HPF) that showed highest concentrations of IgG4-positive cells. Clinical followup data were obtained and correlated with immunohistochemical findings.
Results: Clinical followup showed 5 cases to be AIP (including 1 presumed) and 35 cases to be non-autoimmune pancreatitis or various other pancreatic disorders including 6 cases of neoplasms (non-AIP). The number of IgG4-positive plasma cells per HPF ranged from 0.33 to 65.7 (40.1±25.8) in the AIP group and from 0 to 22 (3.1±6.0) in the non-AIP group (p<0.0001). In the AIP group, 4 (except for the presumed case) showed IgG4 counts ranging from 29.3 to 65.7 (50±13.2). In the non-AIP group, only 6 (17%) cases showed ≥5 IgG4-positive cells/HPF, ranging from 7.7 to 22 (15.1±5.4). Three (50%) of these cases had clinical followup diagnoses of idiopathic pancreatitis, chronic pancreatitis and primary sclerosing cholangitis. Overall, the likelihood of AIP with ≥5 IgG4-positive cells per HPF was 0.4. The likelihood of AIP increased to 0.8 if the mean IgG4 count was ≥ 20.
Conclusions: Immunostain for IgG4 plasma cells in biliary and ampullary biopsies can serve as a useful adjunct tool in the diagnosis of AIP.
Category: Gastrointestinal

Monday, March 22, 2010 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 83, Monday Morning


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