[Monoclonal B-cell lymphocytosis: physiological entity or preliminary stage of chronic lymphocytic leukaemia?]

Area of Science:

• Hematology
• Oncology
• Immunology

Context:

• Recent changes in diagnostic criteria for chronic lymphocytic leukaemia (CLL) emphasize the absolute count of monoclonal B cells.
• The previous reliance on total lymphocyte count has been updated to reflect a more precise diagnostic approach.
• Distinguishing between CLL and a new entity, monoclonal B-cell lymphocytosis (MBL), is now crucial.

Purpose:

• To define the updated diagnostic criteria for chronic lymphocytic leukaemia (CLL).
• To introduce and characterize monoclonal B-cell lymphocytosis (MBL) as a distinct diagnostic entity.
• To outline the clinical course and management recommendations for MBL.

Summary:

• CLL is diagnosed when peripheral blood monoclonal B cells with the characteristic CLL phenotype exceed 5 x 10(9)/l.
• Fewer than 5 x 10(9)/l of these cells indicate MBL, a condition estimated to affect 3% of the population.
• MBL typically follows a mild course with a 1-2% annual progression rate to CLL.

Impact:

• The revised criteria allow for the identification of MBL, a condition requiring less intensive monitoring than CLL.
• Patients with MBL need an initial hematologist evaluation and subsequent annual monitoring by a general practitioner.
• This differentiation aids in appropriate patient management and reduces unnecessary interventions for MBL cases.