title: Histopathological assessment and immunohistochemical study of nasopharyngeal low grade MALT lymphoma.
abstract: BACKGROUND
  MALT lymphoma arises in a variety of body tissues, but most often in the stomach. Though relatively rare, these MALT lymphomas may arise within several sites in the head and neck, and often present diagnostic and therapeutic challenges. Immunohistochemical analysis are helpful in confirming the diagnosis between the MALT-lymphoma and the reactive lymphoid hyperplasia. MALT-type lymphoma demonstrated characteristic negative staining for CD3, CD5 and CD43, positive staining for CD20, and monotypic staining for either kappa or lambda light chain immunoglobulin markers, whereas reactive lymphoid hyperplasia all expressed B and T cell markers.
  
  
  METHODS
  41 Cases of nasopharyngeal masses were obtained from the files at pathology department, Mansoura Faculty of Medicine through the period from 2002 till 2006. 31 cases were corresponded histomorphologically to low-grade B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) type and 10 patients with reactive lymphoid hyperplasia of the adenoid. Hematoxylin- eosin-stained slides were reviewed to confirm the diagnosis. Immunohistochemical studies were performed on formalin-fixed, paraffin-embedded sections using the labeled streptavidin-biotin-peroxidase complex method with DAB as chromogen. The following antibodies were evaluated CD20, CD3, Kappa, lambda and cytokeratin antibodies.
  
  
  RESULTS
  All cases of low grade MALT lymphoma show lymphoepithelial lesion and proliferation of centrocyte like cells. 14 cases (45.1%) show subepithelial plasma cells. Dutcher bodies were demonstrated in 10 cases (32.2%). Monocytoid B-cells were seen in 12 cases (38.7%). Six (60%) out of the ten cases of adenoids show transmigrating lymphocyte without formation of lymphoepithelial lesion. All cases with MALT-type lymphoma expressed CD20 and not CD3 whereas 10 cases of adenoid, all expressed B and T cell markers. Immunohistochemical staining showed that 31 cases of low grade MALT lymphoma were positive for immunoglobin light chain (kappa or lambda) while 10 cases of adenoid were positive for both kappa and lambda light chain.
  
  
  CONCLUSIONS
  Immunohistochemical analysis are helpful in confirming the diagnosis between the MALT-lymphoma and the reactive lymphoid hyperplasia of the nasopharynx.
authors.affiliation: The Department of Pathology, Faculty of Medicine, Mansoura University. amira 960@hotmail.com
authors.forename: Amira Kamal
authors.initials: AK
authors.lastname: El-Hawary
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D018442:Lymphoma, B-Cell, Marginal Zone / Q000175:diagnosis* / Q000473:pathology; D008297:Male; D009303:Nasopharyngeal Neoplasms / Q000175:diagnosis* / Q000473:pathology