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Blood Res 2022; 57(4):
Published online December 31, 2022
https://doi.org/10.5045/br.2022.2022235
© The Korean Society of Hematology
NK-cell trogocytosis of CD19 antigen: a rare B-ALL MRD mimicker
Correspondence to : Narender Tejwani, M.D., Department of Pathology, Rajiv Gandhi Cancer Institute and Research Centre, New Delhi 110085, India, E-mail: mbbsnt@gmail.com
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.
A 10-year-old male patient with B-cell acute lymphoblastic leukemia (B-ALL) came in for a post-induction measurable residual disease (MRD) assessment. The diagnostic immunophenotype was CD19+/CD10+/CD34heterogeneous+/cCD79a+/CD22+/CD20heterogeneous+/CD38Dim+/CD73bright+/CD45-/CD123-/CD86-/CD304-. The bone marrow aspirate sample was processed via a bulk lyse-stain-wash technique using a 10-color antibody panel and 3.3 million events were observed on the BD FACS Lyric flow cytometer. Using the Kaluza software, a suspicious population was identified with an unusual CD19+/CD45bright+/CD38heterogeneous+/CD34-/CD10-/CD20-/CD73-/CD123-/CD22-/ CD86-immunophenotype (A–L). There was no therapeutic history of rituximab use. The presence of a single B-lineage marker, CD19, coupled with the absence of CD10 and CD22 made this population unlikely to be associated with MRD. Considering the bright expression of CD45, a custom tube was processed and the population was found to be CD7+, CD16/CD56+, and sCD3-(M–R); they also showed a CD19 expression, similar to the prior observation. Finally, an MRD negative report was issued; the MRD mimicking cells were attributed to trogocytosis of the CD19 antigen by the NK cells. Diagnostic immunophenotyping revealed a significant clue in this case. NK-cell trogocytosis of the CD19 receptor, the initial gating marker for B-ALL MRD evaluation, though rare, can mimic MRD and should be considered as a differential.
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Image of Hematology
Blood Res 2022; 57(4): 249-249
Published online December 31, 2022 https://doi.org/10.5045/br.2022.2022235
Copyright © The Korean Society of Hematology.
NK-cell trogocytosis of CD19 antigen: a rare B-ALL MRD mimicker
Devasis Panda, Amardeep Pathak, Narender Tejwani, Anurag Mehta
Department of Pathology, Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, India
Correspondence to:Narender Tejwani, M.D., Department of Pathology, Rajiv Gandhi Cancer Institute and Research Centre, New Delhi 110085, India, E-mail: mbbsnt@gmail.com
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.
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A 10-year-old male patient with B-cell acute lymphoblastic leukemia (B-ALL) came in for a post-induction measurable residual disease (MRD) assessment. The diagnostic immunophenotype was CD19+/CD10+/CD34heterogeneous+/cCD79a+/CD22+/CD20heterogeneous+/CD38Dim+/CD73bright+/CD45-/CD123-/CD86-/CD304-. The bone marrow aspirate sample was processed via a bulk lyse-stain-wash technique using a 10-color antibody panel and 3.3 million events were observed on the BD FACS Lyric flow cytometer. Using the Kaluza software, a suspicious population was identified with an unusual CD19+/CD45bright+/CD38heterogeneous+/CD34-/CD10-/CD20-/CD73-/CD123-/CD22-/ CD86-immunophenotype (A–L). There was no therapeutic history of rituximab use. The presence of a single B-lineage marker, CD19, coupled with the absence of CD10 and CD22 made this population unlikely to be associated with MRD. Considering the bright expression of CD45, a custom tube was processed and the population was found to be CD7+, CD16/CD56+, and sCD3-(M–R); they also showed a CD19 expression, similar to the prior observation. Finally, an MRD negative report was issued; the MRD mimicking cells were attributed to trogocytosis of the CD19 antigen by the NK cells. Diagnostic immunophenotyping revealed a significant clue in this case. NK-cell trogocytosis of the CD19 receptor, the initial gating marker for B-ALL MRD evaluation, though rare, can mimic MRD and should be considered as a differential.
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