Issue Highlights – January 2020

This January 2020 issue of Clinical Cytometry B includes 7 original articles, 2 brief communications, 1 review, and 1 letter to the editor. The issue is predominated by original study articles in hematolymphoid malignancies Wang and colleagues (1) reported a large series of extranodal NK/T cell lymphoma, nasal type (ENKTL-N) from the west part of China. The authors showed that flow cytometry immunophenotyping not only could assist in diagnosis but also discriminate cellular lineages (NKvs T-), evaluate activation status of NK-cells, and assess potential therapy targets of ENKTL-N. Through thorough characterization, the authors identified a number of immunophenotypical characteristics facilitating a ready distinction of ENKTL-N from reactive NK/T cells. We have longed for a simple straightforward T cell clonality assessment, reminiscent Kappa/ Lambda for B cell clonality. Currently, TCR Vβ repertoire analysis by flow cytometry (2–4) uses 24 antibodies recognizing 70% Vβ repertoires, which is laborintensive, costly, and with limited sensitivity. Shi and colleagues (5) from Mayo Clinic reported their experience in using single anti-TRBC1 antibody for TCRβ clonality assessment. The authors showed that all 20 Tcell malignancies (TCRβ) exhibited a monophasic TRBC1 expression (100% sensitivity); whereas, 44 patients without T-cell malignancies showed an expected mixture of TRBC1-positive and TRBC1-negative subpopulations (non-clonal). The use of single antibody TRBC1 allows the integration of clonality assessment with immunophenotyping, together, hopefully provides a simple, rapid and reliable method in the detection of T-cell neoplasms. T-cell/histiocyte rich large B cell lymphoma (THRLBCL) is a large B cell lymphoma with rare neoplastic B-cells embedded in a reactive infiltrate that conventional flow cytometry is unable to detect B-lymphoma cells. For the first time, Glynn and colleagues (6) characterized the immunophenotype of lymphoma cells in THRLBCL through flow cytometric cell sorting technology. CD40, CD50 and CD54 were found over-expressed, likely contributing to the predominance of T cells in THRLBCL. Cherian et al (7) previously reported frequent CD3 +CD4+CD7-bright/CD45-bright T-cell subpopulations in primary mediastinal large B cell lymphoma (PMLBCL). In the letter to editor, Gadgeel and colleagues (8) communicated their observation of CD20+ T cells in two cases of PMLBCL. CD20+ T cells with highly activated Th17 cells that may contribute to the PMLBCL microenvironment. Apparently, atypical Tcell proliferation is common in PMLBCL, and it is important not to misinterpret as T cell lymphoma. There are two studies on bone marrow (BM) hematogones (immature precursor B cells) in this issue. Daratumumab is an IgG1-kappa monoclonal antibody that targets CD38, which has obtained FDA approval for refractory myeloma patients, and recently as frontline therapy in combination with bortezomib, melphalan and prednisone for patients ineligible for transplant (9). Due to bright CD38 expression on hematogones, artifactual kappa light chain restriction was observed, and the findings were summarized in the study by Jiang and coauthors (10). Kappa-restricted CD10+ hematogones might result in a false interpretation of a concurrent clonal B cell proliferation. In the era of rapidly growing list of therapeutic monoclonal antibodies, diagnosticians should be aware of potential interferences. On the other hand, hematogones are often markedly decreased or completely absent in the BMs of patients with myelodysplastic syndromes (MDS) (11), and the finding is considered as an important feature for MDS by flow cytometry immunophenotyping. However, preservation of hematogones is observed in some cases of MDS; have you ever wondered if it has any clinical and biological significance? Chen and colleagues (12) studied 160 treatment naïve low grade MDS and reported the perseveration of stage I hematogones in over a quarter of the patients. This biological phenomenon was associated with MDS with Sa A. Wang [Color figure can be viewed at wileyonlinelibrary.com]