title: CD4-positive diffuse large B cell lymphoma identified by flow cytometry: two case reports.
abstract: We report two cases of diffuse large B cell lymphoma (DLBCL), both occurring in the small bowel, which coexpress PAX5, weak or no CD20 and the CD4 antigen. The CD4 was initially identified by flow cytometry and then confirmed by immunohistochemistry. CD4 is a representative marker for helper T-lymphocytes and is present on a subset of thymocytes, peripheral T cells and monocytes or macrophages. Unlike CD2 and CD5, no B cell fractions are known to express CD4. It might be hypothesized that the deregulated control of gene expression in malignant B cells, in particular PAX5, leads to the activation of some silent or repressed genes of T cell differentiation. Although lineage infidelity is described in some B lymphomas, it remains as an uncommon phenomenon; to our knowledge, cases reported here are the first two cases of DLBCL of the gastrointestinal tract coexpressing the CD4 antigen to be described to date.
authors.affiliation: Laboratory of Pathology, Department of Pathology, Molinette Hospital, via Santena 7, Turin, Italy.
authors.forename: Marisa
authors.initials: M
authors.lastname: Arrondini
authors.forename: Antonella
authors.initials: A
authors.lastname: Barreca
authors.forename: Sabrina
authors.initials: S
authors.lastname: Aliberti
authors.forename: Anna
authors.initials: A
authors.lastname: Demurtas
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Tondat
authors.forename: Domenico
authors.initials: D
authors.lastname: Novero
authors.forename: Alessandra
authors.initials: A
authors.lastname: Stacchini
mesh_terms: D000368:Aged; D001402:B-Lymphocytes / Q000473:pathology; D015704:CD4 Antigens; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007150:Immunohistochemistry; D016403:Lymphoma, Large B-Cell, Diffuse / Q000175:diagnosis* / Q000276:immunology; D008297:Male; D008875:Middle Aged
chemical_list: D015704:CD4 Antigens