Diagnostic criteria for monoclonal B-cell lymphocytosis

Br J Haematol. 2005 Aug;130(3):325-32. doi: 10.1111/j.1365-2141.2005.05550.x.


Very low levels of circulating monoclonal B-cell subpopulations can now be detected in apparently healthy individuals using flow cytometry. We propose the term 'monoclonal B-cell lymphocytosis' (MBL) to describe this finding. The aim of this document is to provide a working definition of MBL for future clinical, epidemiological and laboratory studies. We propose that the detection of a monoclonal B-cell population by light chain restriction is sufficient to define this condition in individuals not meeting the diagnostic criteria for other B-lymphoproliferative disorders. The majority of individuals with MBL will have cells that are indistinguishable from chronic lymphocytic leukaemia (CLL). However, this blood cell clonal expansion of CD5+ or CD5- B-lymphocytes is age-dependent and immunophenotypic heterogeneity is common. Longitudinal studies are required to determine whether MBL is a precursor state to CLL or other B-lymphoproliferative disease in a situation analogous to a monoclonal gammopathy of undetermined significance and myeloma. Future studies of MBL should be directed towards determining its relationship to clinical disease, particularly in individuals from families with a genetic predisposition to developing CLL.

Publication types

  • Review

MeSH terms

  • Adolescent
  • Adult
  • Antigens, CD19 / analysis
  • B-Lymphocytes / immunology
  • CD5 Antigens / analysis
  • Clone Cells
  • Disease Progression
  • Genetic Predisposition to Disease
  • Humans
  • Immunophenotyping
  • Lymphoma, B-Cell / diagnosis*
  • Lymphoma, B-Cell / genetics
  • Lymphoma, B-Cell / immunology
  • Middle Aged
  • Receptors, IgE / analysis
  • Time Factors


  • Antigens, CD19
  • CD5 Antigens
  • Receptors, IgE