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Monoclonal B-cell lymphocytosis: from literature to laboratory practice

2016; John Libbey Eurotext; Volume: 74; Issue: 2 Linguagem: Inglês

10.1684/abc.2016.1127

1950-6112

Aurore Keutgens, Jacques Foguenne, André Gothot, Françoise Tassin,

Monoclonal and Polyclonal Antibodies Research

Monoclonal B-cell lymphocytosis (MBL) is defined as an asymptomatic condition characterized by the presence of less than 5,000 monoclonal B-cells per microliter and the absence of clinical signs or symptoms of a B-cell lymphoproliferative disorder. Most MBL cases involve B cells presenting an identical phenotype to CLL (CLL-like MBL) with a Catovsky-Matutes score of 3 to 5 and share the same chromosomal abnormalities than CLL. Depending on the absolute B cell count, one may distinguish low-count CLL-like MBL ( 500 B cells/μL) have a 1% to 2% per year risk of progression to CLL requiring therapy, a higher risk of infectious complications and mortality implicating an annual follow-up by hematologist. MBL may also express other less common phenotypes and are named atypical MBL in case of CD5 antigen expression (Catovsky-Matutes score: 1-2) and non-CLL-like MBL for CD5 negative cases (Catovsky-Matutes score: 0-2). Their poorer prognosis implicates imaging studies, bone marrow biopsy and cytogenetic analysis in addition to physical examination in order to rule out non-hodgkinien lymphoma, and require a more frequent follow-up. This review focuses on key concepts in the classification, diagnosis, monitoring and biology of MBL in laboratory practice.