Overexpression of CD7 in classical Hodgkin lymphoma-infiltrating T lymphocytes

Abstract

Background: Diagnosis of Hodgkin lymphoma (HL) is sometimes complicated by the scarcity of neoplastic cells in a reactive inflammatory background. Immunophenotyping by flow cytometry (FC) has not played a significant role in HL diagnosis because of its consistent failure to identify these neoplastic cells. However, HL-infiltrating T cells have been shown to play a role in HL pathogenesis. This study characterizes the FC immunophenotype of these T lymphocytes to determine whether they can be used to assist in the diagnosis of HL. Methods: Cell suspensions from 76 lymph nodes involved by HL and 156 lymph nodes with reactive lymphadenopathy (LAD) were analyzed by flow cytometry to assess the expression of T-cell antigens. Results: The CD4:CD8 ratio and CD7 expression in both CD4(+) and CD8(+) T cells are increased in HL compared with reactive lymph nodes and there are significant differences between these features in different subtypes of HL. However, only the expression of CD7 in CD4(+) T cells distinguishes between HL and reactive LAD. This is especially true for classical HL in younger patients. Using a CD7 mean fluorescence intensity (MFI) cutoff value generated by this data, 37/47 FNA specimens were correctly diagnosed. Conclusions: There are significant differences in the immunophenotypes of HL-infiltrating T cells. Of these, the CD7 expression in CD4(+) T cells discriminates between HL and reactive LAD, suggesting that this could be a useful and practical adjunctive tool in the diagnosis of HL. It may also further our understanding of the pathophysiology of this disease. © 2008 Clinical Cytometry Society.