Flow cytometry CD45‐negative B‐NHL: A case report of a diffuse large B‐cell lymphoma without extranodal involvement

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. © 2012 International Clinical Cytometry Society