Are tumefactive lesions classified as sclerosing mesenteritis a subset of IgG4-related sclerosing disorders?

Abstract

Background: The relationship between tumefactive lesions classified as sclerosing mesenteritis and IgG4-related sclerosing disorders (e.g. lymphoplasmacytic sclerosing pancreatitis/autoimmune pancreatitis) remains uncertain.

Aims: In this study, lesions coded as “sclerosing mesenteritis” were reviewed for findings in keeping with IgG4-related sclerosing disorders.

Methods: Inclusion in the study required available paraffin blocks for IgG4 staining and documentation of a mass lesion.

Results: A total of nine mesenteric lesions ranging from 3-14 cm were identified in 6 male and 3 female patients. On hematoxylin and eosin-stained sections, all were characterized as loosely marginated fibroinflammatory processes with variable amounts of fat necrosis. Lymphocytic venulitis/phlebitis was identified in 8 of 9 cases. IgG and IgG4 expression in lesional plasma cells was assessed by immunohistochemistry (IHC). IgG4-positive plasma cells were counted in the areas of greatest density in ³ 3 high power fields (HPFs). The highest number per HPF was recorded and a score assigned based on the following scale: <5/HPF- none/minimal; 5-10/HPF-mild; 11-30/HPF- moderate; >30/HPF- marked. The relative proportion of IgG4-reactive plasma cells to total IgG-positive plasma cells was assessed. IgG4-reactive plasma cells ranged from 0 to >100 in the most dense zones (3 cases- none/minimal, 4 cases- moderate, 2 cases- marked).

Conclusions: Although this study is limited by small numbers, our findings suggest that some tumefactive lesions regarded as sclerosing mesenteritis may be a subset of IgG4-related sclerosing disorders.