title: 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 (eg, lymphoplasmacytic sclerosing pancreatitis/autoimmune pancreatitis) remains uncertain.
  
  
  OBJECTIVE
  To review lesions coded as "sclerosing mesenteritis" 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 (3-14 cm) were identified in 6 male and 3 female patients. On H&E-stained sections, all were characterised 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. IgG4-positive plasma cells were counted in the areas of greatest density in >or=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, findings suggest that some tumefactive lesions regarded as sclerosing mesenteritis may be a subset of IgG4-related sclerosing disorders.
authors.affiliation: Department of Pathology, The Johns Hopkins Medical Institutions, Baltimore, Maryland 21231, USA.
authors.forename: T S
authors.initials: TS
authors.lastname: Chen
authors.forename: E A
authors.initials: EA
authors.lastname: Montgomery
mesh_terms: D000328:Adult; D000368:Aged; D001158:Arteries / Q000276:immunology / Q000473:pathology; D002452:Cell Count; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis; D007150:Immunohistochemistry; D008214:Lymphocytes / Q000276:immunology / Q000473:pathology; D008297:Male; D008875:Middle Aged; D015436:Panniculitis, Peritoneal / Q000276:immunology / Q000473:pathology*; D010689:Phlebitis / Q000276:immunology / Q000473:pathology; D010950:Plasma Cells / Q000276:immunology / Q000473:pathology*; D013194:Staining and Labeling; D014680:Veins / Q000276:immunology / Q000473:pathology
chemical_list: D007074:Immunoglobulin G