Reactive T Cells by Flow Cytometry Distinguish Hodgkin Lymphomas from T Cell/Histiocyte-Rich Large B Cell Lymphoma

Background: Classical Hodgkin lymphoma (CHL), nodular lymphocyte predominant Hodgkin lymphoma (NLPHL), and T-cell/histiocyte rich large B-cell lymphoma (T/HRLBCL) are B-cell lymphomas in which tumor cells are rare as compared with the background reactive infiltrate. We hypothesized that characterization of the reactive infiltrates can provide information to help diagnose these lymphomas. Methods: Lymphocyte subsets by flow cytometry were analyzed for 27 NLPHL, 20 T/HRLBCL, 34 CHL, and 49 reactive lymph nodes (RLN). CD4+ T cells with bright expression of CD7 and CD45 (CD3+CD4+CD7(bright)CD45(bright)), CD4:CD8 ratio, and percentage of T cells, B cells, NK cells, CD4+ T cells, CD8+ T cells, T cells coexpressing CD4, and CD8 (CD4+CD8+), and plasma cells were measured. Results: The CD3+CD4+CD7(bright)CD45(bright) T-cell population was present in the reactive infiltrate of CHL (76.5%) and T/HRLBCL (92.3%) but not in NLPHL (8.3%) or RLN (4.1%). In a separate analysis of 387 samples, the CD3+CD4+CD7(bright)CD45(bright) T-cell population was also observed in some CD10+ B-NHL. The mean percentage of CD4+CD81 T cells was highest for NLPHL (11.7%) and differed significantly from T/HRLBCL, CHL, and RLN. Interestingly, the highest CD4: CD8 ratios were seen with T/HRLBCL. Finally, the percentage of B cells is decreased in T/HRLBCL relative to CHL and NLPHL. Conclusions: Differences in the reactive inflammatory infiltrate of CHL, NLPHL, and T/HRLBCL and can suggest these diagnoses. Additionally, in contrast to published studies, T/HRLBCL demonstrates both low and very high CD4 to CD8 T-cell ratios. (C) 2015 International Clinical Cytometry Society