Ann Lab Med 2020; 40(5): 409-413  https://doi.org/10.3343/alm.2020.40.5.409
Prevalence and Immunophenotypic Characteristics of Monoclonal B-Cell Lymphocytosis in Healthy Korean Individuals With Lymphocytosis
In Young Yoo, M.D.1, Sung Hoan Bang, M.T.1, Dae Jin Lim, M.T.1, Seok Jin Kim, M.D.2, Kyunga Kim, Ph.D.3,4, Hee Jin Kim, M.D.1, Sun-Hee Kim, M.D.1, and Duck Cho, M.D.1
1Department of Laboratory Medicine and Genetics; 2Division of Hematology and Oncology, Department of Medicine; 3Statistics and Data Center, Research Institute for Future Medicine; 4Department of Digital Health, Samsung Advanced Institute for Health Sciences and Technology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
Corresponding author: 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
E-mail: duck.cho@skku.edu
Received: September 23, 2019; Revised: November 13, 2019; Accepted: March 20, 2020; Published online: September 1, 2020.
© Korean Society for Laboratory Medicine. All rights reserved.

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.
Abstract
Epidemiological studies of monoclonal B-cell lymphocytosis (MBL) have been conducted in limited geographical regions. Little is known about the prevalence of MBL in Asia. We investigated the prevalence and immunophenotypic characteristics of MBL in Koreans who had idiopathic lymphocytosis (lymphocyte count >4.0×109/L) and were ≥40 years of age. A total of 105 leftover peripheral blood samples met these criteria among those from 73,727 healthy individuals who visited the Health Promotion Center, Samsung Medical Center, Korea, from June 2018 to August 2019. The samples were analyzed using eight-color flow cytometry with the following monoclonal antibodies: CD45, CD5, CD10, CD19, CD20, CD23, and kappa and lambda light chains. The overall prevalence of MBL in the study population was 2.9% (3/105); there was one case of chronic lymphocytic leukemia (CLL)-like MBL (CD5+CD23+), one case of atypical CLL-like MBL (CD5+CD23), and one case of CD5MBL with a lambda restriction pattern. This is the first study on the MBL prevalence in an East Asian population, and it reveals a relatively low prevalence of MBL in healthy Korean individuals with lymphocytosis.
Keywords: Chronic lymphocytic leukemia, Monoclonal B-cell lymphocytosis, Prevalence, Immunophenotype, Korea



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