[1371] Sclerosing Inflammatory Pseudotumor of the Orbit: An IgG4-Related Disease

VE Klepeis, V Deshpande, AR Sohani, JA Ferry. Massachusetts General Hospital, Boston, MA

Background: Autoimmune pancreatitis (AIP) is a sclerosing inflammatory disease associated with an elevated proportion of IgG4-expressing plasma cells. Recent evidence suggests that IgG4-related sclerosing disease can affect a variety of sites other than pancreas. Inflammatory orbital pseudotumors present with a range of histopathologic patterns similar to AIP, often containing numerous plasma cells. In this study we investigate IgG4 expression in plasma cells within inflammatory orbital pseudotumors.
Design: Twenty-one cases of orbital pseudotumor diagnosed between 2004 and 2009 were reviewed. In addition to characterizing histopathologic patterns, we constructed tissue microarrays from 5-mm cores of representative areas and performed immunohistochemistry for IgG and IgG4 to quantify the proportion of IgG4-positive plasma cells.
Results: Thirteen patients were female and eight were male, and the median age was 60 years (range 7 to 77 years). Glandular structures were present in 5 of 21 cases, indicating lacrimal gland involvement. Histopathologic features of the pseudotumors ranged from predominantly reactive lymphoid hyperplasia to fibrosclerosis varying from septal to diffuse with marked hypocellularity. The more reactive-appearing cellular orbital pseudotumors contained well-developed lymphoid follicles and a mixed inflammatory infiltrate, often including abundant plasma cells (13/21 cases) and many scattered eosinophils (8/21 cases). Germinal centers were negative for bcl2 by immunohistochemistry, consistent with reactive follicles. Phlebitis was observed in 6 cases. Overall, 16 of 21 cases (76%) showed an increased percentage of IgG4-positive plasma cells with a mean percentage of 85 (range 50 to 100%). Patients with more sclerotic orbital pseudotumors were less likely to display abundant IgG4-positive plasma cells.
Conclusions: Orbital pseudotumors not only have a similar morphology to AIP, but many also contain numerous IgG4-positive plasma cells, especially when more florid reactive lymphoid hyperplasia is present. Our findings suggest that many cases of orbital pseudotumor belong to the category of IgG4-related diseases. Immunostaining for IgG4 may be used to help establish a diagnosis of orbital pseudotumor.
Category: Hematopathology

Tuesday, March 23, 2010 9:30 AM

Poster Session III # 214, Tuesday Morning


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