Monoclonal B-cell lymphocytosis (MBL)
- Method:
- Anticoagulant:
- Recommendation:
- Method:Cytomorphology
- Anticoagulant:EDTA
- Recommendation:obligatory
- Method:Immunophenotyping
- Anticoagulant:EDTA or Heparin
- Recommendation:obligatory
- Method:Chromosome analysis
- Anticoagulant:
- Recommendation:no
- Method:FISH
- Anticoagulant:EDTA or Heparin
- Recommendation:facultative
- Method:Molecular genetics
- Anticoagulant:EDTA or Heparin
- Recommendation:facultative
B-cell monoclonal lymphocytosis is an optional preliminary stage of chronic lymphocytic leukemia. We have summarized the most important information on (sub)classification, diagnosis and risk of progression. In addition, we provide further links on prognosis and monitoring in MBL, so that you can inform yourself in more detail.
Monoclonal B-cell lymphocytosis: classification
According to the WHO classification 2022, monoclonal B-cell lymphocytosis belongs to the mature B-cell neoplasms and is here classified as 'pre-neoplastic and neoplastic small-cell lymphoid proliferative diseases', which also includes chronic lymphocytic leukemia (CLL). Depending on the phenotype, three types of monoclonal B-cell lymphocytosis are distinguished (WHO 2022):
- Low-count MBL: monoclonal B-cell population of CLL phenotype in peripheral blood <0.5 x 109 /L, no other diagnostic signs of lymphoproliferative B-cell disease
- CLL-type MBL: monoclonal B-cell population of CLL phenotype in peripheral blood ≥0.5 x 109 /L, absolute B-cell count <5 x 109 /L, no other diagnostic signs of CLL
- Non-CLL-type MBL: any monoclonal B-cell expansion without CLL phenotype, no symptoms or diagnostic evidence of any other mature B-cell neoplasia
Monoclonal B-cell lymphocytosis: diagnostic methods and their significance
Monoclonal B-cell lymphocytosis: prognosis
Clinical course in MBL depends on lymphocyte count at diagnosis
All subtypes of MBL are characterized by immune system impairment, manifested by suboptimal response to vaccination and increased risk of infection (Moreira et al. 2013, Criado et al. 2018, Shanafelt et al. 2021, Whitaker et al. 2021, Muchtar et al. 2022, WHO 2022).
In the low-count variant, progression to CLL is extremely rare (Fazi et al. 2011, Vardi et al. 2013, Shim et al. 2014). ). In contrast, the risk of progression is significantly increased (74-fold) in CLL-type MBL (Slager et al. 2022), with a rate of progression to CLL of 1-2% per year (Rawstron et al. 2008, Shanafelt et al. 2010, Vardi et al. 2013, Shim et al. 2014, Parikh et al. 2018). The development of highly malignant lymphoma is also possible in rare cases (Parikh et al. 2018). In addition, there appears to be an approximately twofold increased risk of developing non-hematologic cancers (Solomon et al. 2016). Overall, MBL patients with CLL-type MBL also show a survival disadvantage compared with individuals without MBL (Slager et al. 2022).
The CLL-IPI has prognostic significance also in MBL
For patients with CLL-type MBL, a correlation between CLL-IPI score and time to indication for therapy was found (Kleinstern et al. 2020). In another study, differences in time to first therapy as well as differences in overall survival were observed for the different risk groups according to CLL-IPI (Parikh et al. 2021).
Monoclonal: B-cell lymphocytosis: prognosis calculation
Monoclonal: B-cell lymphocytosis: Recommendation
For patients with CLL-type monoclonal B-cell lymphocytosis, the control recommendation of the German guideline is based on the lymphocyte count. For low-count MBL, a single control after 6-12 months is recommended. For CLL-type MBL, regular controls every 6-12 months are indicated (Onkopedia guideline MBL 2021). For patients with CLL-atypical MBL or CD5-negative MBL, screening every 6-12 months is also recommended (Rawstron et al. 2009, Shanafelt et al. 2010).
Status: September 2023