Current Hematologic Malignancy Reports

, Volume 8, Issue 1, pp 52–59 | Cite as

Monoclonal B Cell Lymphocytosis—What Does It Really Mean?

Chronic Leukemias (S O’Brien, Section Editor)


Monoclonal B cell Lymphocytosis (MBL) or similar terms have been used for decades to describe the presence of light-chain restricted B lymphocytes with uncertain clinical significance, usually having a phenotype consistent with chronic lymphocytic leukemia (CLL). As diagnostic technology improved, ever smaller monoclonal B cell populations were identifiable in the population, and approximately half of people over 90 years old have a minimal (<1 cell/μL) circulating CLL-like B cell population. These minimal CLL-like B cell populations share some molecular characteristics with CLL, but have no clinical significance. In contrast, CLL-like MBL cases detected through hospital investigations are biologically indistinguishable from early stage CLL, but the neoplastic B cell levels are usually stable over time and the risk of progressive disease requiring treatment is much lower than for early stage CLL. However, there is usually partial or complete depletion of normal B cells, with an increased relative risk of severe infection, comparable to early stage CLL, which may impair overall survival.


MBL CLL Infection Survival 



A. Rawstron: Consultancy work for Biogen Idec.


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Copyright information

© Springer Science+Business Media New York 2013

Authors and Affiliations

  1. 1.HMDS, St. James’s Institute of OncologyLeeds Teaching Hospitals NHS TrustLeedsUK

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