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BioMed Research International
Volume 2014, Article ID 258917, 11 pages
Review Article

New Insights into Monoclonal B-Cell Lymphocytosis

1Department of Haematology, University Hospital, University of Crete, P.O. BOX 1352, 71110 Heraklion, Crete, Greece
2Department of Haematology, Athens Medical Center-Psychikon Branch, 11525 Athens, Greece
3Department of Haematology, University of Athens, Laikon General Hospital, 11527 Athens, Greece
4Department of Pathology, University of Athens, 11527 Athens, Greece
5Department of Haematology, 401 Military Hospital, 11525 Athens, Greece
61st Department of Propedeutics, University of Athens, Laikon General Hospital, 11527 Athens, Greece

Received 17 April 2014; Accepted 21 July 2014; Published 11 September 2014

Academic Editor: Kazuyuki Shimizu

Copyright © 2014 Christina Kalpadakis et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Monoclonal B-cell lymphocytosis (MBL) is a premalignant condition characterized by the presence of less than 5000/μL circulating clonal B cells in otherwise healthy individuals. Three subcategories have been identified according to the immunophenotypic features: CLL-like, CD5(+) atypical, and CD5(−) MBL. CLL-like MBL is by far the most frequent and best studied category and further divided in low-count [LC] and high-count [HC] MBL, based on a cutoff value of 500/μL clonal B cells. LC-MBL typically remains stable and probably does not represent a truly premalignant condition, but rather an age-related immune senescence. On the other hand, HC-MBL is closely related to CLL-Rai0, bearing similar immunogenetic profile, and is associated with an annual risk of progression to CLL requiring therapy at a rate of 1.1%. Currently there are no reproducible factors for evaluating the risk of progression to CLL. CD5(−) MBL is characterized by an immunophenotype consistent with marginal zone origin and displays many similarities with marginal zone lymphomas (MZL), mainly the splenic MZL. The cutoff value of 5000/μL clonal B cells cannot probably be applied in CD5(−) MBL, requiring a new definition to describe those cases.