title: Extranodal mantle cell lymphoma mimicking marginal zone cell lymphoma.
abstract: OBJECTIVE
  We report a case of mantle cell lymphoma masquerading as a marginal zone cell lymphoma.
  
  
  RESULTS
  In the initial manifestation in the palatine tonsils, the neoplastic cells were found to grow exclusively within the marginal zones of secondary follicles which showed a preserved mantle zone. The few immunostains performed showed a B-cell phenotype including an immunoglobulin light chain restriction. The extranodal manifestation, the growth pattern, and the immunophenotype led to the diagnosis of an extranodal marginal zone B-cell non-Hodgkin's lymphoma (NHL). The specimen from the relapse occurring 8 months later exhibited diffuse monomorphous cells co-expressing B-cell antigens and CD5, CD43 and cyclin D1, leading to the diagnosis of mantle cell lymphoma. Re-investigation of the initial biopsy revealed that the neoplastic cells within the marginal zones had a mantle cell lymphoma immunophenotype expressing cyclin D1, the immunoglobulin heavy chains IgD and IgM and partly CD5. Both lesions harboured identical clonal immunoglobulin gene rearrangements proving that they represented different manifestations of the same lymphoma.
  
  
  CONCLUSIONS
  This case emphasizes the importance of broad immunohistological investigation of B-cell NHLs involving the marginal zone.
authors.affiliation: Consultation and Reference Centre for Haematopathology, Institute of Pathology, Klinikum Benjamin Franklin, Free University Berlin, Hindenburgdamm 30, D-12200 Berlin, Germany.
authors.forename: I
authors.initials: I
authors.lastname: Anagnostopoulos
authors.forename: H D
authors.initials: HD
authors.lastname: Foss
authors.forename: M
authors.initials: M
authors.lastname: Hummel
authors.forename: G
authors.initials: G
authors.lastname: Trenn
authors.forename: H
authors.initials: H
authors.lastname: Stein
mesh_terms: D015703:Antigens, CD; D018956:CD5 Antigens / Q000032:analysis; D019938:Cyclin D1 / Q000032:analysis; D003937:Diagnosis, Differential; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000032:analysis; D007150:Immunohistochemistry; D051917:Leukosialin; D016393:Lymphoma, B-Cell / Q000378:metabolism / Q000473:pathology*; D020522:Lymphoma, Mantle-Cell / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D012795:Sialoglycoproteins / Q000032:analysis
chemical_list: D015703:Antigens, CD; D018956:CD5 Antigens; D007143:Immunoglobulin Heavy Chains; D051917:Leukosialin; C465014:SPN protein, human; D012795:Sialoglycoproteins; D019938:Cyclin D1