Monoclonal B cell lymphocytosis--what does it really mean?

Understanding Monoclonal B Cell Lymphocytosis: An Interplay of Genetic and Microenvironmental Factors

The term monoclonal B-cell lymphocytosis (MBL) describes the presence of a clonal B cell population with a count of less than 5 × 10⁹/L and no symptoms or signs of disease. Based on the B cell count, MBL is further classified into 2 distinct subtypes: 'low-count' and 'high-count' MBL. High-count MBL shares a series of biological and clinical features with chronic lymphocytic leukemia (CLL), at least of the indolent type, and evolves to CLL requiring treatment at a rate of 1-2% per year, whereas 'low-count' MBL seems to be distinct, likely representing an immunological rather than a pre-malignant condition. That notwithstanding, both subtypes of MBL can carry 'CLL-specific' genomic aberrations such as cytogenetic abnormalities and gene mutations, yet to a much lesser extent compared to CLL. These findings suggest that such aberrations are mostly relevant for disease progression rather than disease onset, indirectly pointing to microenvironmental drive as a key contributor to the emergence of MBL. Understanding microenvironmental interactions is therefore anticipated to elucidate MBL ontogeny and, most importantly, the relationship between MBL and CLL.

Monoclonal B-cell lymphocytosis in blood donors in Turkey

OBJECTIVES

Monoclonal B-cell lymphocytosis (MBL) is a precursor state of chronic lymphocytic leukemia (CLL) with peripheral lymphocytosis below 5 × 10⁹/l. The diagnostic criteria exclude the presence of lymphadenopathy, organomegaly, infections, autoimmune diseases or any sign of a lymphoproliferative disorder. This prospective study was designed in order to evaluate the frequency of MBL in blood donors in Turkey.

METHODS

The diagnosis of MBL was identified by flow cytometry method based on the International Familial CLL Consortium Report. A total of 999 volunteers [median age 34 (18-78) years; male/female: 705/294] were included in the study.

RESULTS

Monoclonal B-cell lymphocytosis was demonstrated in 18 cases (1.8%). A total of 16 cases (1.6%) was evaluated as CLL-like MBL, while 2 (0.2%) had a non-CLL-like phenotype. The subjects were divided into three groups according to age, as <40 years, 40-60 years and >60 years. The prevalence of MBL was 1.1% below 40 years, 0.6% between 40 and 60 years and 0.1% in cases over 60 years, without statistical significance (p > 0.05).

DISCUSSION

The sensitivity of the flow cytometry method is essential and may be responsible for the variations in the prevalence of MBL in different populations which can also be attributed to study design, higher detection rates in the elderly and families with genetic predisposition to CLL.

CONCLUSION

Large population-based studies and standardized laboratory methods are needed to determine the potential risk factors of progression to CLL, including molecular markers and genetic profile.

Comparison of microRNA expression in high-count monoclonal B-cell lymphocytosis and Binet A chronic lymphocytic leukemia

Background

Evidence suggests that monoclonal B-cell lymphocytosis precedes all chronic lymphocytic leukemia cases, although the molecular mechanisms responsible for disease progression are not understood. Aberrant miRNA expression may contribute to the pathogenesis of chronic lymphocytic leukemia. The objective of this study was to compare miRNA expression profiles of patients with Binet A chronic lymphocytic leukemia with those of subjects with high-count monoclonal B-cell lymphocytosis and healthy volunteers (controls).

Methods

Twenty-one chronic lymphocytic leukemia patients, 12 subjects with monoclonal B-cell lymphocytosis and ten healthy volunteers were enrolled in this study. Flow cytometry CD19⁺CD5⁺-based cell sorting was performed for the chronic lymphocytic leukemia and monoclonal B-cell lymphocytosis groups and CD19⁺ cells were sorted to analyze the control group. The expressions of miRNAs (miR-15a, miR-16-1, miR-29b, miR-34a, miR-181a, miR-181b and miR-155) were determined by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR).

Results

Significant differences between the expressions in the chronic lymphocytic leukemia and monoclonal B-cell lymphocytosis groups were restricted to the expression of miR-155, which was higher in the former group. A comparison between healthy controls and monoclonal B-cell lymphocytosis/chronic lymphocytic leukemia patients revealed higher miR-155 and miR-34a levels and lower miR-15a, miR-16-1, miR-181a and miR-181b in the latter group.

Conclusions

Our results show a progressive increase of miR-155 expression from controls to monoclonal B-cell lymphocytosis to chronic lymphocytic leukemia. The role of miR-155 in the development of overt chronic lymphocytic leukemia in individuals with monoclonal B-cell lymphocytosis must be further analyzed.

Monoclonal B-cell lymphocytosis in the population of Slovenian region of Lower Carniola

INTRODUCTION

Monoclonal B-cell lymphocytosis (MBL) is a premalignant asymptomatic condition characterized by the presence of a small population of monoclonal B lymphocytes (less than 5 × 10(9) /L) in the venous blood of otherwise healthy individuals. Incidence of MBL is higher among first-degree relatives of patients with chronic lymphocytic leukemia (CLL) and also increases with age and among men. We compared the incidence of MBL found in the same environment in both an open general population and relatives of CLL patients.

METHODS

Samples were analyzed with 5-parameter flow cytometry using following monoclonal antibodies: kappa and lambda clonality, CD5, CD19, CD20. We analyzed 216 samples of patients in the Slovenian area of Lower Carniola aged 23-88 years. Fifty-four patients who came from families where CLL is present were compared by age and gender to 162 healthy individuals from the general population of the same region.

RESULTS

We found 10 cases of MBL (4.6%). In 9.4% of younger (≤ 50 years) first-degree relatives of CLL patients with immunophenotypic characteristics of atypical MBL, we observed a prevailingly normal κ to λ ratio. The difference in incidence of MBL cases between relatives and the general population decreases with age.

CONCLUSION

MBL in Slovenia can be coincidentally found with a similar frequency to previously studied populations of other parts of Europe. We found, however, a higher incidence of atypical MBL among first-degree relatives.

Lymphocytosis, lymphadenopathy: benign or malignant?

The increasing use of immunophenotypic and molecular analysis in the routine evaluation of patients with lymphocytosis, lymphadenopathy, or other hematologic disorders has led to the identification of unexpected small clonal lymphoid populations. These clones, sometimes with disease-specific markers, such as the t(14;18), are especially challenging for the clinician because of their unknown biologic potential and uncertain clinical behavior. Study of these early lymphoid lesions is providing important clues to the process of lymphomagenesis, and may provide the rationale for preemptive therapy in the future. More and more, the hematologist/oncologist is consulted regarding otherwise healthy individuals with lymphadenopathy and/or lymphocytosis, and pathology reports that confound the referring internist or surgeon. The report does not name a malignant lymphoproliferative disorder, but is not completely “normal”. Does the patient have a benign or malignant condition? How should they be evaluated? Is treatment indicated? These patients prove challenging for the consulting hematologist as well as the referring physician. In this review, we will focus on some of these scenarios and attempt to provide guidance for their management.

Monoclonal B-cell lymphocytosis in individuals from sporadic (non-familial) chronic lymphocytic leukemia families persists over time, but does not progress to chronic B-cell lymphoproliferative diseases

Background

Monoclonal B-cell lymphocytosis is classified as ‘high-count or clinical’ monoclonal B-cell lymphocytosis and ‘low-count or population’ monoclonal B-cell lymphocytosis. Previously, 167 first-degree relatives pertaining to sporadic (non-familial) chronic lymphocytic leukemia families were studied and the presence of seven monoclonal B-cell lymphocytosis individuals was reported.

Objective

The aim of this report is to describe the outcomes of five of the original monoclonal B-cell lymphocytosis individuals.

Methods

Flow cytometry analysis was performed on mononuclear cells previously isolated from peripheral blood samples. A strategy of sequential gating designed to identify the population of CD19⁺/CD5⁺ B-lymphocytes was used and, subsequently, the monoclonal B-cell lymphocytosis cells were characterized by the CD20^weak/CD79b^{weak/negative} phenotype.

Results

The monoclonal B-cell lymphocytosis clone showed consistent stability over time with little variations in size. After a median follow-up of 7.6 years, none of the five monoclonal B-cell lymphocytosis individuals progressed to chronic lymphocytic leukemia or other B-cell lymphoproliferative disease.

Conclusions

The data of this study suggest that chronic lymphocytic leukemia-like monoclonal B-cell lymphocytosis detected in the context of sporadic chronic lymphocytic leukemia families is not prone to clinical evolution and could be just a sign of immune senescence.

Early lymphoid lesions: conceptual, diagnostic and clinical challenges

There are no "benign lymphomas", a fact due to the nature of lymphoid cells to circulate and home as part of their normal function. Thus, benign clonal expansions of lymphocytes are only rarely recognized when localized. Recent studies have identified a number of lymphoid proliferations that lie at the interface between benign and malignant. Some of these are clonal proliferations that carry many of the molecular hallmarks of their malignant counterparts, such as BCL2/IGH and CCND1/IGH translocations associated with the in situ forms of follicular lymphoma and mantle cell lymphoma, respectively. There are other clonal B-cell proliferations with low risk of progression; these include the pediatric variants of follicular lymphoma and marginal zone lymphoma. Historically, early or incipient forms of T/NK-cell neoplasia also have been identified, such as lymphomatoid papulosis and refractory celiac disease. More recently an indolent form of T-cell lymphoproliferative disease affecting the gastrointestinal tract has been described. Usually, CD8(+), the clonal cells are confined to the mucosa. The clinical course is chronic, but non-progressive. NK-cell enteropathy is a clinically similar condition, composed of cytologically atypical NK-cells that may involve the stomach, small bowel or colon. Breast implant-associated anaplastic large cell lymphoma is a cytologically alarming lesion that is self-limited if confined to the seroma cavity. Atypical lymphoid proliferations that lie at the border of benign and malignant can serve as instructive models of lymphomagenesis. It is also critical that they be correctly diagnosed to avoid unnecessary and potentially harmful therapy.

Lag times between lymphoproliferative disorder and clinical diagnosis of chronic lymphocytic leukemia: a prospective analysis using plasma soluble CD23

BACKGROUND

Chronic lymphocytic leukemia (CLL) is a chronic disease that often progresses slowly from a precursor stage, monoclonal B-cell lymphocytosis (MBL), and that can remain undiagnosed for a long time.

METHODS

Within the European Prospective Investigation into Cancer cohort, we measured prediagnostic plasma sCD23 for 179 individuals who eventually were diagnosed with CLL and an equal number of matched control subjects who remained free of cancer.

RESULTS

In a very large proportion of CLL patients' plasma sCD23 was clearly elevated 7 or more years before diagnosis. Considering sCD23 as a disease predictor, the area under the ROC curve (AUROC) was 0.95 [95% confidence interval (CI), 0.90-1.00] for CLL diagnosed within 0.1 to 2.7 years after blood measurement, 0.90 (95% CI, 0.86-0.95) for diagnosis within 2.8 to 7.3 years, and 0.76 (95% CI, 0.65-0.86) for CLL diagnosed between 7.4 and 12.5 years. Even at a 7.4-year and longer time interval, elevated plasma sCD23 could predict a later clinical diagnosis of CLL with 100% specificity at >45% sensitivity.

CONCLUSIONS

Our findings provide unique documentation for the very long latency times during which measurable B-cell lymphoproliferative disorder exists before the clinical manifestation of CLL.

IMPACT

Our findings have relevance for the interpretation of prospective epidemiologic studies on the causes of CLL in terms of reverse causation bias. The lag times indicate a time frame within which an early detection of CLL would be theoretically possible. Cancer Epidemiol Biomarkers Prev; 24(3); 538-45. ©2014 AACR.

Clonal B-cell lymphocytosis exhibiting immunophenotypic features consistent with a marginal-zone origin: is this a distinct entity?

Clonal B-cell lymphocytosis of potential marginal-zone origin (CBL-MZ) rarely progresses to a well-recognized lymphoma. CBL-MZ does not require treatment in the absence of progressive disease.

Developments in the immunophenotypic analysis of haematological malignancies

Immunophenotyping is the method by which antibodies are used to detect cellular antigens in clinical samples. Although the major role is in the diagnosis and classification of haematological malignancies, applications have expanded over the past decade. Immunophenotyping is now used extensively for disease staging and monitoring, to detect surrogate markers of genetic aberrations, to identify potential immuno-therapeutic targets and to aid prognostic prediction. This expansion in applications has resulted from developments in antibodies, methodology, automation and data handling. In this review we describe recent advances in both the technology and applications for the analysis of haematological malignancies. We highlight the importance of the expanding repertoire of testing capability for diagnostic, prognostic and therapeutic applications. The impact and significance of immunophenotyping in the assessment of haematological neoplasms are evident.