[1441] The Role of Biopsies in the Diagnosis of Autoimmune Pancreatitis (Lymphoplasmacytic Sclerosing Pancreatitis)

K Notohara, TC Smyrk, N Mizuno, M Mino-Kenudson. Kurashiki Central Hospital, Kurashiki, Japan; Mayo Clinic, Rochester, MN; Aichi Cancer Center Hospital, Nagoya, Japan; Massachusetts General Hospital, Boston, MA

Background: Lymphoplasmacytic sclerosing pancreatitis (LPSP) represents the pancreatic manifestation of IgG4-related systemic fibrosclerosing diseases and appears to be the most prevalent subtype of autoimmune pancreastitis (AIP). Because of the difficulty in differentiating AIP from pancreatic cancer clinically, pancreatic biopsy is now being considered as an attractive diagnostic tool. The aim of our study was to evaluate the accuracy and interobserver concordance of the biopsy diagnosis of LPSP.
Design: 69 pancreatic biopsies (35 fine needle aspiration biopsies [FNABs], 32 trucut biopsies [TCBs] and 2 excisional biopsies) diagnosed as non-neoplastic diseases were collected. Without clinical information, 3 pathologists categorized each biopsy as diagnostic of LPSP (group 1, G1), suspicious but not diagnostic of LPSP (group 2, G2), or not suggestive of LPSP (group 3, G3). Insufficient biopsies were also noted as such. Both diagnoses made before and after reviewing IgG4-immunostain (IG4-IS), when it was available (n=22), were recorded. The pathologic diagnoses were correlated with clinical records.
Results: 21 FNABs were considered as insufficient materials by 2 or more pathologists, and were excluded from further analysis. Each pathologist categorized 14, 16 and 10 of the remaining 48 biopsies as G1, and 7, 16 and 13 as G2. Without IG4-IS, the complete agreements of G1 and G3 were achieved in 4 and 14 biopsies, respectively. value for G1 was only fair (0.34), although all observers agreed that periductal inflammation, obliterative phlebitis and storiform fibrosis were the diagnostic hallmarks for G1 diagnosis of LPSP. With IG4-IS, value for G1 improved to 0.43 (moderate). When G1 and G2 were grouped together (G1/2), the complete agreement of G1/2 was achieved in 17 biopsies ( value 0.50 [moderate]). G1/2 diagnosis was made on 26 of 32 TCBs by 2 or more pathologists, and 25 of these cases carried a clinical diagnosis of AIP. Clinical AIP was also seen in 4 of the remaining 6 patients with TCBs. G1/2 diagnosis by 2 or more pathologists was not achieved in any of 14 FNABs, although 9 of these patients had clinical AIP.
Conclusions: Diagnosis of LPSP on biopsies is challenging, most likely because small tissue samples fail to contain diagnostic hallmarks for LPSP. However, TCB (with IG4-IS) appears to be a useful tool to support the clinical diagnosis of AIP.
Category: Liver & Pancreas

Wednesday, March 11, 2009 9:30 AM

Poster Session V # 220, Wednesday Morning