[1574] Distinction of Lymphoplasmacytic Sclerosing Pancreatitis from Other Mass-Forming Inflammatory Diseases by CD163 and Α-Smooth Muscle Actin Immunohistochemistry.

Kenji Notohara, Lizhi Zhang, Katsuyuki Miyabe, Shu Nakamoto, Takahiro Nakazawa. Kurashiki Central Hospital, Japan; Mayo Clinic, Rochester, MN; Nagoya City University Graduate School of Medical Sciences, Japan; Tottori Prefectural Central Hospital, Tottori, Japan

Background: Lymphoplasmacytic sclerosing pancreatitis (LPSP) and idiopathic duct-centric pancreatitis (IDCP) are recognized as different clinicopathologic entities, and have recently been designated as type 1 and type 2 autoimmune pancreatitis (AIP), respectively. However, histological distinction of LPSP and IDCP is sometimes difficult even for pathologists who are familiar with AIP. CD163+ macrophages are a major component of storiform fibrosis that characterizes LPSP, and therefore CD163 may be useful for the differential diagnosis.
Design: Resected specimens of LPSP (21 patients), IDCP (12), and mass-forming chronic pancreatitis, not otherwise specified (MCP; 17) were gathered. Immunostaining for CD163 and α-smooth muscle actin (ASMA) was carried out with a representative block.
Results: In 17 cases with LPSP, spindle-shaped CD163+ macrophages were numerous, and formed bundle-shaped aggregates that corresponded to storiform fibrosis. Proliferation of CD163+ macrophages, which was observed mainly in the lobules and peripancreatic adipose tissue, and sometimes in the pancreatic ducts, was so prominent that the borders of these structures were often obscure. ASMA, however, could highlight the borders of relatively well-preserved pancreatic lobules. In the remaining 4 cases with LPSP, CD163+ cells were less numerous, and did not form bundle-shaped aggregates, suggesting a regression process of LPSP. Even so, these cells were more numerous than those in IDCP and MCP. In IDCP, CD163+ macrophages were seen isolated in the fibrotic areas and occasionally in the lobules and ducts. Aggregates of CD163+ macrophages were sometimes encountered, but usually consisted of more plump cells. Obliteration of the pancreatic structures by proliferating macrophages was not a feature of IDCP. The distribution of ASMA+ cells in IDCP was denser compared to that in LPSP. CD163+ cells were a few in cases with MCP.
Conclusions: Bundle-shaped aggregates of spindle-shaped macrophages that obscure the pancreatic structures are a characteristic and diagnostic feature of LPSP that correspond to storiform fibrosis. CD163 is useful for recognizing this pattern.
Category: Liver & Pancreas

Wednesday, March 2, 2011 9:30 AM

Poster Session V # 205, Wednesday Morning


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