Predominance of CD4+ T Cells in TCell/ Histiocyte-Rich Large B-Cell Lymphoma and Identification of a Subset of Patients with Peripheral B-Cell Lymphopenia

Objectives: T-cell/histiocyte-rich large B-cell lymphoma (THRLBCL) is a morphologic variant of large B-cell lymphoma whose flow cytometry findings are not well characterized. Methods: Nineteen cases with flow cytometric immunophenotyping were identified from the case records of four institutions between 2001 and 2016. Results: In most cases, neoplastic B cells were not detected by flow cytometry. Overall, cases showed a predominance of CD4+ T cells, which in some cases was marked. Significant coexpression of CD57 was seen on CD4+ T cells where this marker was analyzed, which correlated with PD-1 expression. Two cases also showed a profound systemic B-cell lymphopenia, which was associated in one case with hypogammaglobulinemia. Conclusions: Overall, our work challenges previous findings that cases of THRLBCL are rich in CD8+ T cells and highlights parallels between THRLBCL and nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL). Also, an association of THRLBCL with systemic B-cell lymphopenia has not been previously reported but may represent an underrecognized manifestation.