title: Flow cytometry CD45-negative B-NHL: a case report of a diffuse large B-cell lymphoma without extranodal involvement.
abstract: BACKGROUND
  The loss of CD45, the leukocyte-common antigen, has been described in rare cases of large B-cell lymphoma (LBCL) subtypes with extranodal involvement by immunohistochemical methods. Here we report a case of a patient with LBCL, with no extranodal lesions, which is CD45 negative by flow cytometry (FC) immunophenotyping.
  
  
  METHODS
  Immunophenotyping and DNA content analysis was performed by multiparametric FC on lymph node and bone marrow aspirate obtained from a 65 year old male patient.
  
  
  RESULTS
  Malignant B-lymphocytes were CD5-, CD10+/++, CD11c-, CD19+, CD20+/++, CD23-, CD34-, CD38-/+, CD45-, CD79b++/+++, BCL2 overexpressed, FMC7++, IgM++/+++, TdT- with Lambda light chain restriction. This pathological cellular population showed near-diploid DNA content, with a high proliferate rate.
  
  
  CONCLUSIONS
  To our knowledge, we describe the first case of a CD19+ B-cell non-Hodgkin lymphoma without expression of CD45 detected by FC, and the first case without extranodal involvement presentation. This case is reported not only because it is a rare one but also to raise awareness of FC users of its correct diagnosis.
authors.affiliation: Flow Cytometry Laboratory, Department of Hematology, IPO-Porto, Porto, Portugal. palmeira.ca@gmail.com
authors.forename: Carlos
authors.initials: C
authors.lastname: Palmeira
authors.forename: Maria Emília
authors.initials: ME
authors.lastname: Sousa
authors.forename: Inês
authors.initials: I
authors.lastname: Godinho
authors.forename: Ana Marta
authors.initials: AM
authors.lastname: Pires
authors.forename: Carlos
authors.initials: C
authors.lastname: Mendes
authors.forename: Gabriela
authors.initials: G
authors.lastname: Martins
mesh_terms: D000368:Aged; D015703:Antigens, CD / Q000032:analysis / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology; D001706:Biopsy; D001853:Bone Marrow / Q000276:immunology; D049109:Cell Proliferation; D004253:DNA Nucleotidylexotransferase / Q000032:analysis / Q000276:immunology; D005434:Flow Cytometry / Q000379:methods*; D006023:Glycoproteins / Q000032:analysis; D006801:Humans; D007075:Immunoglobulin M / Q000032:analysis; D016130:Immunophenotyping / Q000379:methods; D017493:Leukocyte Common Antigens / Q000032:analysis / Q000276:immunology / Q000378:metabolism*; D008198:Lymph Nodes / Q000276:immunology; D016403:Lymphoma, Large B-Cell, Diffuse / Q000175:diagnosis* / Q000276:immunology / Q000473:pathology; D008297:Male
chemical_list: D015703:Antigens, CD; D006023:Glycoproteins; D007075:Immunoglobulin M; C112523:MS4A1 protein, human; D004253:DNA Nucleotidylexotransferase; D017493:Leukocyte Common Antigens; C516769:PTPRC protein, human