Letter to the Editor
Ann Lab Med 2021; 41(6): 598-600
Published online November 1, 2021 https://doi.org/10.3343/alm.2021.41.6.598
Copyright © Korean Society for Laboratory Medicine.
Aberrant Loss of Surface CD3 and TCRγδ Expression in Relapsed Hepatosplenic T-cell Lymphoma
1Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea; 2Division of Hematology-Oncology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
Correspondence to: Duck Cho, M.D.
Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-ro, Gangnam-gu, Seoul 06351, Korea
Tel: +82-2-3410-2403, Fax: +82-2-3410-2719
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Hepatosplenic T-cell lymphoma (HSTL) is an aggressive extranodal lymphoma that originates from cytotoxic γδ T cells [1, 2]. HSTL patients typically present with hepatosplenomegaly in the absence of lymphadenopathy [1, 2]. Morphologically, HSTL is characterized by sinusoidal infiltration of the spleen, liver, and bone marrow (BM) with monotonous medium-sized neoplastic lymphoid cells; isochromosome 7q is a recurrent cytogenetic abnormality detected in most HSTL cases [1, 2]. The typical immunophenotype of HSTL is as follows: CD2+, sCD3+, CD4–, CD5–, CD7+, CD8–, and T-cell receptor (TCR)γδ+ . However, there have been reports of rare HSTL cases with loss of sCD3 and TCRγδ, posing a major challenge in establishing an accurate diagnosis and determining relapse [3–6]. We report a rare case of HSTL with an unusual immunophenotype characterized by loss of sCD3 and TCRγδ expression at relapse. Unlike previously reported cases, the abnormal cells in our case were positive for CD16 and CD56 and, therefore, could be easily misinterpreted as natural killer (NK) cells. The Institutional Review Board of Samsung Medical Center, Seoul, Korea, approved this study (approval number: 2020-07-154) and waived the need for informed consent.
A 57-year-old man visited Samsung Medical Center in September 2019 for fever of unknown origin (FUO). The complete blood count (CBC) result was as follows: hemoglobin, 81 g/L; white blood cell count, 3.38×109/L (without definite abnormal lymphoid cells); and platelet count, 204×109/L. The abdominopelvic computed tomography scan revealed hepatosplenomegaly, with a spleen size of 16 cm. During the FUO workup, a BM biopsy was performed, which led to the diagnosis of mature γδ T-cell lymphoma without an identifiable primary focus. In the initial study, the BM aspirate showed 5–10% of medium-sized abnormal lymphoid cells with pleomorphic nuclei and prominent nucleoli. Flow cytometry was performed using a FACSLyric flow cytometer (Becton Dickinson, San Jose, CA, USA) after staining the BM mononuclear cells with monoclonal antibodies against T- and NK-cell associated antigens, and data were analyzed using the Kaluza software (Beckman Coulter Inc., Miami, FL, USA). Flow cytometry revealed an abnormal T-cell population with the following immunophenotype: sCD3+, cCD3+, CD4-, CD8-, CD56+, CD16+, CD2+, CD5–, CD7+, CD94+, CD57–, and TCRγδ+ (Fig. 1). Chromosomal analysis indicated a normal karyotype (46,XY), and a
Figure 1. Flow cytometry findings in both (A) initial and (B) follow-up studies. (A) Abnormal lymphoid cells highlighted in red exhibited the sCD3+, CD4-, CD8-, and TCRγδ+ phenotype at diagnosis, (B) whereas they exhibited the sCD3-, CD4-, CD8-, and TCRγδ- phenotype at relapse. The cells highlighted in blue and green are normal CD4+ T cells and CD8+ T cells, respectively. The CD4dim+ population observed at relapse (B) was probably made up of monocytes.
Abbreviations: BM, bone marrow; TCR, T-cell receptor.
The patient underwent multiple cycles of chemotherapy with four different regimens. During the course of chemotherapy, splenectomy and cholecystectomy were performed, and spleen pathology revealed γδ T-cell lymphoma. A follow-up BM study was conducted six months after the initial diagnosis, and the CBC result was as follows: hemoglobin, 105 g/L; white blood cell count, 10.22×109/L (10% abnormal lymphoid cells); and platelet count, 244×109/L. The BM aspirate showed 20% abnormal lymphoid cells, and their immunophenotype, determined by flow cytometry, was sCD3–, cCD3+, CD4–, CD8–, CD56+, CD16+, CD2+, CD5–, CD7+, CD94+, CD57–, and TCRγδ– (Fig. 1); in contrast to the initial findings, loss of sCD3 and TCRγδ was noted. Two possibilities were considered: 1) an unusual immunophenotypic shift to abnormal T cells lacking sCD3 and TCRγδ and 2) an increased proportion of reactive NK cells. A positive
Compared with previous cases, determining disease relapse was very challenging in the present case because of CD56 positivity and simultaneous loss of sCD3 and TCRγδ expression, which made the abnormal lymphoid cells from this case difficult to distinguish from reactive NK cells. In such cases, a meticulous review of cell morphology, cytogenetic studies, and molecular studies should be conducted. Morphologically, immunohistochemistry for granzyme B and perforin could be useful, as these proteins are not expressed in HSTL but are expressed in aggressive NK-cell leukemia (ANKL) [2, 4]. Conversely, HSTL cases could be positive for TIA-1 expression [2, 4]. Identification of isochromosome 7q and
While flow cytometry provides powerful insights into neoplastic cell lineage, it may be a double-edged sword in cases where lineage-specific markers are aberrantly lost, since it could lead to the misclassification of cell lineages. Hematopathologists should always consider the possibility of unusual immunophenotypic changes. Since only a few such cases have been reported to date, the fact that HSTL can present without expression of sCD3 and TCRγδ is not well known. Hence, we present this diagnostically challenging case to share our experience and highlight the fact that T-lineage lymphoma cells with loss of T-cell markers could be mistakenly identified as NK cells in flow cytometry.
We would like to acknowledge Sung Hoan Bang, M.T. for conducting the flow cytometry.
Lee B wrote the manuscript. All authors contributed to data interpretation. Kim HY and Cho D critically reviewed the manuscript. All authors have read and approved the final version of the manuscript.
CONFLICTS OF INTEREST
There are no potential conflicts of interest relevant to this article to report.
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