title: Immunohistochemical profile of lymphoid lesions of the orbit.
abstract: Orbital idiopathic inflammation, lymphoid hyperplasia, and lymphoma may all present clinically in the same manner. Histopathology and especially immunohistochemistry play a major role in the differential diagnosis. The purpose of this study was to determine the immunophenotypic features of these lesions.
  
  
  
  Fifty-five orbital lymphoid lesions were retrieved from the ophthalmic pathology registries at McGill University, Montreal, Canada, and the Federal University of São Paulo, São Paulo, Brazil. Formalin-fixed, paraffin-embedded, histopathologic sections were stained with hematoxylin and eosin and periodic acid-Schiff. The sections were also immunostained for B-cell (CD20) and T-cell (CD43) markers and for immunoglobulin light chains kappa and lambda. Two pathologists determined the histopathologic and immunohistochemical pattern of each lesion in a masked fashion.
  
  
  
  Of the 55 lesions, 11 (20%) were idiopathic chronic inflammations, 22 (40%) were lymphoid hyperplasias and 22 (40%) were lymphomas. Idiopathic inflammation displayed a predominance of T cells and all lesions expressed polyclonal light chains. Lymphoid hyperplasia displayed a mixture of B cells and T cells, with a slight predominance of the former and all lesions expressed polyclonal light chains. Lymphoma showed a striking predominance of B cells and all lesions expressed monoclonal light chains, usually kappa (63.7%). The differences in the mean percentages of B cells among the orbital lymphoid lesions (inflammation, 35%; hyperplasia, 65.9%; lymphoma, 87.3%) were statistically significant (p < 0.001).
  
  
  
  Orbital lymphoid lesions can be differentiated based on the percentages of B cells and T cells and the monoclonal or polyclonal expression of immunoglobulin light chains.
authors.affiliation: The Department of Pathology, Federal University of São Paulo, Brazil.
authors.forename: Marcia S
authors.initials: MS
authors.lastname: Lowen
authors.forename: Vinicius S
authors.initials: VS
authors.lastname: Saraiva
authors.forename: Maria C
authors.initials: MC
authors.lastname: Martins
authors.forename: Miguel N
authors.initials: MN
authors.lastname: Burnier
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D018951:Antigens, CD20 / Q000378:metabolism; D018952:Antigens, CD34 / Q000378:metabolism; D001402:B-Lymphocytes / Q000473:pathology; D014408:Biomarkers, Tumor / Q000378:metabolism; D005260:Female; D006801:Humans; D007145:Immunoglobulin kappa-Chains / Q000378:metabolism; D007146:Immunoglobulin lambda-Chains / Q000378:metabolism; D007150:Immunohistochemistry; D016130:Immunophenotyping; D008223:Lymphoma / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009918:Orbital Neoplasms / Q000378:metabolism / Q000473:pathology*; D016727:Orbital Pseudotumor / Q000378:metabolism / Q000473:pathology*; D019310:Pseudolymphoma / Q000378:metabolism / Q000473:pathology*; D013601:T-Lymphocytes / Q000473:pathology
chemical_list: D018951:Antigens, CD20; D018952:Antigens, CD34; D014408:Biomarkers, Tumor; D007145:Immunoglobulin kappa-Chains; D007146:Immunoglobulin lambda-Chains