Monoclonal B lymphocytes with the characteristics of "indolent" chronic lymphocytic leukemia are present in 3.5% of adults with normal blood counts

Chronic Lymphocytic Leukemia, Small Lymphocytic Lymphoma, and Monoclonal B-Cell Lymphocytosis

Chronic lymphocytic leukemia (CLL), small lymphocytic lymphoma (SLL), and monoclonal B-cell lymphocytosis (MBL) are clonal proliferations of small, mature B cells. CLL and SLL are considered neoplastic, although they are indolent and many patients with these lymphomas never require treatment. Most MBL cases share immunophenotypic and genetic features with CLL and SLL but have a small burden of clonal cells. This review focuses on the pathologic features of CLL, SLL, and MBL and their differential diagnoses. Guidelines are provided to separate the entities from one another and to avoid pitfalls in distinguishing these entities from other lymphomas and from reactive lymphoid proliferations.

Silencing of the inhibitor of DNA binding protein 4 (ID4) contributes to the pathogenesis of mouse and human CLL

Inhibitor of DNA binding protein 4 (ID4) is a member of the dominant-negative basic helix-loop-helix transcription factor family that lacks DNA binding activity and has tumor suppressor function. ID4 promoter methylation has been reported in acute myeloid leukemia and chronic lymphocytic leukemia (CLL), although the expression, function, and clinical relevance of this gene have not been characterized in either disease. We demonstrate that the promoter of ID4 is consistently methylated to various degrees in CLL cells, and increased promoter methylation in a univariable analysis correlates with shortened patient survival. However, ID4 mRNA and protein expression is uniformly silenced in CLL cells irrespective of the degree of promoter methylation. The crossing of ID4(+/-) mice with Eμ-TCL1 mice triggers a more aggressive murine CLL as measured by lymphocyte count and inferior survival. Hemizygous loss of ID4 in nontransformed TCL1-positive B cells enhances cell proliferation triggered by CpG oligonucleotides and decreases sensitivity to dexamethasone-mediated apoptosis. Collectively, this study confirms the importance of the silencing of ID4 in murine and human CLL pathogenesis.

NCI First International Workshop on the Biology, Prevention, and Treatment of Relapse after Allogeneic Hematopoietic Stem Cell Transplantation: Report from the Committee on Treatment of Relapse after Allogeneic Hematopoietic Stem Cell Transplantation

Relapse is a major cause of treatment failure after allogeneic hematopoietic stem cell transplantation (alloHSCT). Treatment options for relapse have been inadequate, and the majority of patients ultimately die of their disease. There is no standard approach to treating relapse after alloHSCT. Withdrawal of immune suppression and donor lymphocyte infusions are commonly used for all diseases; although these interventions are remarkably effective for relapsed chronic myelogenous leukemia, they have limited efficacy in other hematologic malignancies. Conventional and novel chemotherapy, monoclonal antibody therapy, targeted therapies, and second transplants have been utilized in a variety of relapsed diseases, but reports on these therapies are generally anecdotal and retrospective. As such, there is an immediate need for well-designed, disease-specific trials for treatment of relapse after alloHSCT. This report summarizes current treatment options under investigation for relapse after alloHSCT in a disease-specific manner. In addition, recommendations are provided for specific areas of research necessary in the treatment of relapse after alloHSCT.

Identical IGHV-D-J gene rearrangement may precede the clinical onset of chronic lymphocytic leukemia by several years

The pathogenesis of chronic lymphocytic leukemia (CLL) has not been fully elucidated. Moreover, the time required for the initial B lymphocyte IGH gene rearranged clone to manifest as a clinical entity remains unknown. We searched for previous IGH gene rearranged B lymphocyte clones in healthy people who developed CLL and estimated the time for the clone to become clinically detectable. To this aim, we identified all incident cases of CLL diagnosed in a cohort of 15,055 healthy subjects aged 18-65 years enrolled in a prospective survey on thrombophilia. Seven CLL cases were identified at a median follow-up of 54 months (range, 18-89). The estimated incidence was 0.46 cases/10,000 person-years (CI: 0.17-1.00). A PCR was performed to detect IGH gene rearrangement at enrollment and at CLL diagnosis. Comparison was possible in six subjects. In five, the same IGH gene rearrangement and gene sequence were already present 39-89 months before CLL diagnosis. A mutated status was identified in four of five cases. The median age at diagnosis was 66.2 years, and all subjects were asymptomatic. Two patients expressing the IGHV1-69 gene with an unmutated status required treatment 16 and 40 months after diagnosis. The IGHV4 family genes were rearranged in the remaining cases, all showing a mutated status. No additional rearrangements or mutations in the rearranged gene were found during follow-up. An identical clonal IGH gene rearrangement may precede CLL diagnosis by several years.

Common occurrence of monoclonal B-cell lymphocytosis among members of high-risk CLL families

Monoclonal B-cell lymphocytosis (MBL) is an asymptomatic haematological condition characterized by low absolute levels of B-cell clones with a surface immunophenotype similar to that of chronic lymphocytic leukaemia (CLL). In the general population, MBL increases with age with a prevalence of 5-9% in individuals over age 60 years. It has been reported to be higher among first-degree relatives from CLL families. We report results of multi-parameter flow cytometry among 505 first-degree relatives with no personal history of lymphoproliferative disease from 140 families having at least two cases of CLL. Seventeen percent of relatives had MBL. Age was the most important determinant where the probability for developing MBL by age 90 years was 61%. MBL clustered in certain families but clustering was independent of the number of known CLL cases in a family. As is the case with CLL, males had a significantly higher risk for MBL than did females (P = 0·04). MBL patients had significantly higher mean absolute lymphocyte counts (2·4 × 10(9) /l) and B-cell counts (0·53 × 10(9) /l) than those with a normal B-cell immuno-phenotype. Our findings show that MBL occurs at a very high rate in high risk CLL families. Both the age and gender distribution of MBL are parallel to CLL, implying a shared inherited risk.

Familial chronic lymphocytic leukemia

PURPOSE OF REVIEW

Families with multiple individuals affected with chronic lymphocytic leukemia (CLL) and other related B-cell tumors have been described in the literature and strong familial aggregation has been seen in population studies. However, predisposing germline mutations have not been identified. We will discuss the spectrum of conditions associated with CLL in families and the advances in identifying the underlying susceptibility genes.

RECENT FINDINGS

Familial CLL does not appear to differ substantially from sporadic CLL in terms of prognostic markers and clinical outcome, although it may be associated with more indolent disease. The precursor condition, monoclonal B-cell lymphocytosis, also aggregates in CLL families. Linkage studies have been conducted in high-risk CLL families to screen the whole genome for susceptibility loci but no gene mutations have yet been identified by this method. Association studies of candidate genes have implicated several genes as being important in CLL but more studies are needed. Results from whole-genome association studies are promising.

SUMMARY

The ability to conduct large-scale genomic studies in unrelated CLL patients and in high-risk CLL families will play an important role in detecting susceptibility genes for CLL over the next few years and thereby help to delineate causal pathways.

CLL-like monoclonal B-cell lymphocytosis: are we all bound to have it?

CLL-like monoclonal B-cell lymphocytosis (MBL) shares a unique immunophenotype with chronic lymphocytic leukemia (CLL), and represents the vast majority of clonal B-cell expansions found in the peripheral blood of otherwise healthy subjects. Along with the improvement of laboratory techniques and the widespread availability of multiparameter flow cytometry, the finding of tiny aberrant B-cell populations became more frequent, prompting the need for clinical and biological definition of the nature of this condition and its relationship with leukemia development. MBL seems to be a melting-pot containing several entities, identical in terms of phenotype but with extremely different risks of leukemia development (from low to none) that seem to correlate with the number of B lymphocytes. CLL-like MBL observed in the clinical setting ("Clinical MBL"), usually being characterized by lymphocytosis, demonstrated a sizeable, even if low (1.1-1.4% per year), risk of leukemic progression, but represents a minority of all MBL cases. The vast majority of CLL-like MBL are detected in general population screenings and do not likely have a risk of CLL that is substantially higher than that of unaffected individuals. Interestingly, MBL frequency increases with age, being virtually undetectable under 40 years of age but being present in 50-75% of the people older than 90 years. It has been proposed that MBL could be interpreted as an epiphenomenon of a chronic and persistent antigenic stimulation. The (rare) possibility to evolve into a frank leukemia might then depend on biological and molecular factors insofar unknown that may modify the modality of cell reaction as well as the potential to acquire further genetic abnormalities. Therefore, the real challenge of the next years in the MBL research field is not to increase the sensitivity of detection, neither to implement screening protocols to be applied to the general population, rather to unravel the biologic features that, at individual level, will identify those (few) cases that are at risk of developing a progressive disease.

Genetic variation and risk of chronic lymphocytic leukaemia

Chronic lymphocytic leukaemia (CLL) is the most common form of lymphoid malignancy in Western countries, accounting for around a quarter of all leukaemias. Evidence from epidemiological and family studies have provided evidence for familial clustering of CLL compatible with inherited genetic predisposition to CLL. Direct evidence for genetic susceptibility has been provided by a recent genome wide association study of CLL which has identified common variants at 10 different loci which influence CLL risk. Here we review the current knowledge regarding the allelic architecture of susceptibility to CLL and what the currently identified risk loci are telling us regarding disease aetiology.

Alemtuzumab to treat refractory autoimmune hemolytic anemia or thrombocytopenia in chronic lymphocytic leukemia

Autoimmune hemolytic anemia (AIHA) and immune thrombocytopenic purpura (ITP) are recognized complications of chronic lymphocytic leukemia (CLL) that can be life-threatening if not managed appropriately. Conventional therapies for these autoimmune disorders, such as corticosteroids, splenectomy, and immunosuppressive agents, may not induce complete resolution in all patients, and relapses are common. In recent years, monoclonal antibodies such as alemtuzumab and rituximab, already used successfully for the management of lymphoproliferative disorders, have been shown to be effective in the treatment of a range of autoimmune disorders. The potent antitumor activity of alemtuzumab, in combination with its profound immunosuppressive activity, prompted investigation of its use in patients with severe CLL-related AIHA and ITP. Results from a range of reports confirm the efficacy of alemtuzumab for the treatment of severe, CLL-related autoimmune cytopenias that have failed to respond to conventional therapies and may even be rituximab-refractory.

LEF-1 is a prosurvival factor in chronic lymphocytic leukemia and is expressed in the preleukemic state of monoclonal B-cell lymphocytosis

The canonical Wnt signaling pathway is pathogenic in a variety of cancers. We previously identified aberrant expression of the Wnt pathway transcription factor and target gene lymphoid enhancer binding factor-1 (LEF1) in chronic lymphocytic leukemia (CLL). This suggested that the Wnt signaling pathway has a role in the biology of CLL. In this study, we performed a Wnt pathway analysis using gene expression profiling and identified aberrant regulation of Wnt pathway target genes, ligands, and signaling members in CLL cells. Furthermore, we identified aberrant protein expression of LEF-1 specifically in CLL but not in normal mature B-cell subsets or after B-cell activation. Using the T cell-specific transcription factor/LEF (TCF/LEF) dual luciferase reporter assay, we demonstrated constitutive Wnt pathway activation in CLL, although the pathway was inactive in normal peripheral B cells. Importantly, LEF-1 knockdown decreased CLL B-cell survival. We also identified LEF-1 expression in CD19(+)/CD5(+) cells obtained from patients with monoclonal B-cell lymphocytosis, suggesting a role for LEF-1 early in CLL leukemogenesis. This study has identified the constitutive activation and prosurvival function of LEF-1 and the Wnt pathway in CLL and uncovered a possible role for these factors in the preleukemic state of monoclonal B-cell lymphocytosis.

Autoimmune complications in chronic lymphocytic leukaemia (CLL)

Patients with B-chronic lymphocytic leukaemia /small lymphocytic lymphoma (CLL) have a 5-10% risk of developing autoimmune complications, which primarily cause cytopaenia. These autoimmune cytopaenias can occur at any stage of CLL and do not have independent prognostic significance. The most common autoimmune complication is autoimmune haemolytic anaemia with a lower frequency of immune thrombocytopaenia and pure red blood cell aplasia and only rarely, autoimmune granulocytopaenia (AIG). Autoimmune cytopaenia should always be considered in the differential diagnosis of cytopaenia in patients with CLL. Patients with CLL can also have more than one form of autoimmune cytopaenia, which can occur together with bone-marrow failure. Treatment is usually effective but rarely curative for autoimmune cytopaenia complicating CLL. Optimal therapy will depend on a timely and accurate diagnosis of autoimmune cytopaenia and should be individualised according to the severity of the cytopaenia and the presence or absence of concomitant progressive CLL requiring therapy.

Low levels of monoclonal small B cells in the bone marrow of patients with diffuse large B-cell lymphoma of activated B-cell type but not of germinal center B-cell type

BACKGROUND

Multiparameter flow cytometry allows the detection of minor monoclonal B-cell populations. Using this technique combined with morphology, we were struck by the presence of minor populations of small monoclonal B cells in bone marrows of patients with diffuse large B-cell lymphoma in routine diagnostic samples and performed a systematic retrospective study.

DESIGN AND METHODS

Bone marrows of 165 patients with primary diffuse large B-cell lymphoma without histological evidence of concurrent non-Hodgkin's lymphoma were studied by routine microscopy of trephines and smears, immunohistochemistry and multiparameter flow cytometry.

RESULTS

Diffuse large B-cell lymphoma infiltration in marrows was documented in 11 of 165 patients. Morphological examination consistently revealed a higher tumor load than evidenced by flow cytometry. Of interest, only 3 of 119 patients with diffuse large B-cell lymphoma not otherwise specified, the largest subtype, showed marrow infiltration. By contrast, flow cytometry revealed a minor monoclonal B-cell population in 24 of 165 patients, none of whom showed diffuse large B-cell lymphoma infiltration by morphology. Of interest, morphological examination revealed the presence of small B cells in the marrows of those patients. Moreover, 11 of 39 (28.2%) of patients with diffuse large B-cell lymphoma not otherwise specified of ABC subtype and only 3 of 80 (3.7%) with the GCB subtype showed these monoclonal small B cells (P=0.0002). In addition 4 of 8 (50%), 4 of 15 (26.7%) and 2 of 3 (66.7%) patients with primary testicular, primary central nervous system and leg-type diffuse large B-cell lymphoma, respectively, showed monoclonal small B cells.

CONCLUSIONS

Bone marrow infiltration with diffuse large B-cell lymphoma in patients with diffuse large B-cell lymphoma not otherwise specified is rare at diagnosis. By contrast, a high number of diffuse large B-cell lymphoma not otherwise specified of the ABC subtype but not of GCB subtype is associated with monoclonal small B cells in the marrow. Whether these monoclonal small B cells are precursors of diffuse large B-cell lymphoma of the ABC type or arise in a common background that favors clonal B-cell expansion remains to be demonstrated.

Monoclonal B-cell lymphocytosis (MBL): biology, natural history and clinical management

Chronic lymphocytic leukemia (CLL) and the other low-grade non-Hodgkin lymphomas are among the most common lymphoid malignancies. Recent studies suggest that more than 4% of the general population over age 40 harbor a population of clonal B cells with the phenotype of either CLL or another B-cell malignancy, a condition now designated monoclonal B-cell lymphocytosis (MBL). Although all cases of CLL appear to be preceded by MBL, the majority of individuals with MBL will not develop a hematologic malignancy. The biologic characteristics and clinical implications of MBL appear to differ based on whether it is identified during the diagnostic evaluation of lymphocytosis or incidentally discovered through screening of individuals with normal lymphocyte counts as part of research studies using highly sensitive detection methods. In this paper, we provide a state of the art review on the prevalence, nomenclature, biology, natural history and clinical management of MBL.

From pathogenesis to treatment of chronic lymphocytic leukaemia

Chronic lymphocytic leukaemia (CLL) has several unique features that distinguish it from other cancers. Most CLL tumour cells are inert and arrested in G0/G1 of the cell cycle and there is only a small proliferative compartment; however, the progressive accumulation of malignant cells will ultimately lead to symptomatic disease. Pathogenic mechanisms have been elucidated that involve multiple external (for example, microenvironmental stimuli and antigenic drive) and internal (genetic and epigenetic) events that are crucial in the transformation, progression and evolution of CLL. Our growing understanding of CLL biology is allowing the translation of targets and biological classifiers into clinical practice.

High mitochondrial DNA stability in B-cell chronic lymphocytic leukemia

BACKGROUND

Chronic Lymphocytic Leukemia (CLL) leads to progressive accumulation of lymphocytes in the blood, bone marrow, and lymphatic tissues. Previous findings have suggested that the mtDNA could play an important role in CLL.

METHODOLOGY/PRINCIPAL FINDINGS

The mitochondrial DNA (mtDNA) control-region was analyzed in lymphocyte cell DNA extracts and compared with their granulocyte counterpart extract of 146 patients suffering from B-Cell CLL; B-CLL (all recruited from the Basque country). Major efforts were undertaken to rule out methodological artefacts that would render a high false positive rate for mtDNA instabilities and thus lead to erroneous interpretation of sequence instabilities. Only twenty instabilities were finally confirmed, most of them affecting the homopolymeric stretch located in the second hypervariable segment (HVS-II) around position 310, which is well known to constitute an extreme mutational hotspot of length polymorphism, as these mutations are frequently observed in the general human population. A critical revision of the findings in previous studies indicates a lack of proper methodological standards, which eventually led to an overinterpretation of the role of the mtDNA in CLL tumorigenesis.

CONCLUSIONS/SIGNIFICANCE

Our results suggest that mtDNA instability is not the primary causal factor in B-CLL. A secondary role of mtDNA mutations cannot be fully ruled out under the hypothesis that the progressive accumulation of mtDNA instabilities could finally contribute to the tumoral process. Recommendations are given that would help to minimize erroneous interpretation of sequencing results in mtDNA studies in tumorigenesis.

Single-cell analysis reveals oligoclonality among 'low-count' monoclonal B-cell lymphocytosis

Monoclonal B cell lymphocytosis (MBL) is a pre-clinical hematologic syndrome characterized by small accumulations of CD5⁺ B lymphocytes. Most MBL share phenotypic characteristics with chronic lymphocytic leukemia (CLL). While some MBL progress to CLL, most MBL have apparently limited potential for progression to CLL, particularly those MBL with normal absolute B cell counts (“low count” MBL). Most CLL are monoclonal and it is not known whether MBL are monoclonal or oligoclonal; this is important because it is unclear whether MBL represent indolent CLL or represent a distinct pre-malignant precursor prior to the development of CLL. We used flow cytometry analysis and sorting to determine immunophenotypic characteristics, clonality, and molecular features of MBL from familial CLL kindreds. Single cell analysis indicated 4 of 6 low count MBL consisted of two or more unrelated clones; the other 2 MBL were monoclonal. 87% of low count MBL clones had mutated immunoglobulin genes, and no immunoglobulin heavy chain rearrangements of V_H family 1 were observed. Some MBL were diversified, clonally related populations with evidence of antigen-drive. We conclude that while low count MBL share many phenotypic characteristics with CLL, many MBL are oligoclonal. This supports a model for step-wise development of MBL into CLL.

Familial chronic lymphocytic leukemia: what does it mean to me?

Though B-chronic lymphocytic leukemia (CLL) is known to be a heterogeneous disease, only recently has the familial component of CLL been more thoroughly investigated. This entity is seen in approximately 5%-10% of all patients with CLL and can be associated with earlier age of diagnosis, higher female prevalence, and increased incidence of other lymphoproliferative disorders (LPDs), such as non-Hodgkin lymphoma and the more recently described monoclonal B-cell lymphocytosis CLL in family members. The prognostic parameters and clinical course of familial CLL is not clearly distinguishable from that of sporadic disease. In addition, it is not clear that the treatment responses for progressive disease has any discernible difference in familial versus sporadic CLL. The genetic etiology of CLL is unknown, and early work on familial CLL has not yet uncovered any obvious gene or group of genes that can be clearly related to the pathophysiology of CLL. However, the detailed genetic study of familial CLL is likely to be critical in uncovering relevant genes. At present it is best to indicate to concerned CLL patients that their relatives are at relatively low risk of developing CLL or other LPDs.

The molecular basis of familial chronic lymphocytic leukemia

Our understanding of the genetic basis of chronic lymphocytic leukemia is only just starting to be recognized. This perspective article by Drs. Crowther-Swanepoel and Houlston provides an up-to-date review the molecular epidemiology of chronic lymphocytic leukemia, with emphasis on the integration of biology and genomics.

Synopsis and synthesis of candidate-gene association studies in chronic lymphocytic leukemia: the CUMAGAS-CLL information system

A comprehensive and systematic assessment of the current status of candidate-gene association studies for chronic lymphocytic leukemia (CLL) was conducted. Data from 989 candidate-gene association studies (1992-2009) involving 905 distinct genetic variants were analyzed and cataloged in CUMAGAS-CLL, a Web-based information system which allows the retrieval and synthesis of data from candidate-gene association studies on CLL (http://biomath.med.uth.gr). Nine genetic variants (BAX (rs4645878), GSTM1 (null/present), GSTT1 (null/present), IL10 (rs1800896), LTA (rs909253), MTHFR (rs1801131), MTHFR (rs1801133), P2RX7 (rs3751143), and TNF (rs1800629)) were investigated in 4 or more studies, and their results were meta-analyzed. In individual studies, 147 variants showed a significant association with CLL risk under any genetic model. For 53 variants, the association was significant at P < 0.01 with an increased risk greater than 40%. Only 0.3% of studies had statistical power greater than 80%. In meta-analyses, none of the variants showed significant results, and heterogeneity ranged from none to high. Large and rigorous genetic studies (candidate-gene association studies and genome-wide association studies) designed to investigate epistatic and gene-environment interactions may produce more conclusive evidence about the genetic etiology of CLL. CUMAGAS-CLL would be a useful tool for current genomic epidemiology research in the field of CLL.

Monoclonal B-cell lymphocytosis in first-degree relatives of patients with sporadic (non-familial) chronic lymphocytic leukaemia

Although biological similarities have been described among monoclonal B-cell lymphocytosis (MBL) and chronic lymphocytic leukaemia (CLL), the relationships between these two conditions are not fully understood, and new epidemiological studies in different populations and different countries continue to be reported. Here, we investigated 167 first-degree relatives from 42 families of patients with non-familial (sporadic) CLL, using four-colour flow cytometry. MBL was found in seven of 167 subjects (4.1%). Monoclonality was detected in all cases either by light-chain restriction or by polymerase chain reaction. Fluorescence in situ hybridization did not show any chromosomal abnormality. The prevalence of MBL according to age was 0 (0/54) in individuals aged less than 40 years, 2.5% (2/81) between 40 and 60 years, and 15.6% (5/32) in individuals over 60 years. The prevalence of MBL cases in individuals over 60 years was similar to that found in familial CLL relatives at the same age group. This suggests that in older first-degree relatives of patients with sporadic CLL, the risk of MBL detection is as high as in older first-degree relatives from CLL families, which could render these individuals belonging to 'sporadic CLL families' as susceptible as individuals from 'familial CLL' to the development of clinical CLL.

Monoclonal B lymphocytosis in the general population

Monoclonal B lymphocytosis (MBL) is a frequent phenomenon in the general population. Despite a phenotype similar to chronic lymphocytic leukemia (CLL), the possibility exists that most cases are not necessarily a pre-leukemic condition. This is suggested by the fact that MBL is at least 100 times more frequent than CLL and the diagnosis of CLL is not an inevitable fate, even among MBL cases with lymphocytosis, where it occurs only in 1.1% of the cases per year. The high incidence of MBL, if coupled with the possibility of evolution into a frank leukemic state, poses evident clinical and health system concerns. MBL in the general population usually accounts for a very low number of all circulating B-cells, being <10% of all B lymphocytes. This creates the need for a better characterisation of MBL at molecular level, aiming to identify biological features that may define which cases are more likely to progress towards clinically overt CLL. This approach should also help to avoid unnecessary and prolonged follow-ups in all individuals carrying MBL, excluding those who are extremely unlikely to develop CLL.

Monoclonal B-cell lymphocytosis: definitions and natural history

The diagnostic term monoclonal B-cell lymphocytosis (MBL) is used to characterise individuals with a circulating population of clonal B-cells, a total B-cell count of <5 x 10(9)/L, and no other features of a B-cell lymphoproliferative disorder. The clinical implications of MBL may differ depending on whether an individual with a normal lymphocyte count is identified via a screening assay (screening MBL) or identified through clinical evaluation of lymphocytosis (clinical MBL). The B-cell count used to distinguish between clinical MBL (<5 x 10(9)/L) and CLL (> or = 5 x 10(9)/L) was selected largely based on tradition and technological advances and it is unknown whether the natural history of 'clinical MBL' differs from that of patients with Rai stage 0 CLL. Since, a diagnosis of 'leukemia' may lead to profound psychologic distress for patients, we believe the diagnosis of CLL should be based on an individual's risk of developing symptoms, requiring chemotherapeutic treatment and/or dying of disease. Additional studies are needed to determine whether the clinical outcome of patients with MBL differs from that of patients with Rai stage 0 CLL and to identify what B-cell threshold optimally distinguishes between these conditions.

Brief report: natural history of individuals with clinically recognized monoclonal B-cell lymphocytosis compared with patients with Rai 0 chronic lymphocytic leukemia

PURPOSE

The diagnosis of monoclonal B-cell lymphocytosis (MBL) is used to characterize patients with a circulating population of clonal B cells, a total B-cell count of less than 5 x 10(9)/L, and no other features of a B-cell lymphoproliferative disorder including lymphadenopathy/organomegaly. The natural history of clinically identified MBL is unclear. The goal of this study was to explore the outcome of patients with MBL relative to that of individuals with Rai stage 0 chronic lymphocytic leukemia (CLL).

PATIENTS AND METHODS

We used hematopathology records to identify a cohort of 631 patients with newly diagnosed MBL or Rai stage 0 CLL. Within this cohort, 302 patients had MBL (B-cell counts of 0.02 to 4.99 x 10(9)/L); 94 patients had Rai stage 0 CLL with an absolute lymphocyte count (ALC) < or = 10 x 10(9)/L; and 219 patients had Rai stage 0 CLL with an ALC more than 10 x 10(9)/L. Data on clinical outcome were abstracted from medical records.

RESULTS

The percentage of MBL patients free of treatment at 1, 2, and 5 years was 99%, 98%, and 93%, respectively. B-cell count as a continuous variable (hazard ratio [HR] = 2.9, P = .04) and CD38 status (HR = 10.8, P = .006) predicted time to treatment (TTT) among MBL patients. The likelihood of treatment for MBL patients was lower (HR = 0.32, P = .04) than that of both Rai stage 0 CLL patients with an ALC less than 10 x 10(9)/L (n = 94) and Rai stage 0 CLL patients with an ALC more than 10 x 10(9)/L (n = 219; P = .0003).

CONCLUSION

Individuals with MBL identified in clinical practice have a low risk for progression at 5 years. Because B-cell count seems to relate to TTT as a continuous variable, additional studies are needed to determine what B-cell count should be used to distinguish between MBL and CLL.

Difference in the relative distribution of CD4+ T-cell subsets in B-CLL with mutated and unmutated immunoglobulin (Ig) VH genes: implication for the course of disease

B-cell chronic lymphocytic leukemia (B-CLL) is a clinically heterogeneous disease in which the clinical course is influenced by the presence or absence of immunoglobulin (Ig) variable heavy chain (VH) gene mutations. The poor clinical outcome of the subgroup with unmutated Ig VH genes has been linked to the persistent ability of the B-cell receptor in tumor cells from these cases to respond to antigen. As B-cell receptor signaling generally relies on T-cell help, we hypothesized that the course of B-CLL might not only be influenced by the Ig VH mutational status but also by the activation/differentiation status of T cells. We assessed the relative distribution of naive and memory T-cell subsets in peripheral blood from patients with mutated (M-CLL, n=71) and unmutated Ig VH genes (UM-CLL, n=42) and correlated it with the course of disease. We also compared the prosurvival potential of naive and memory T cells cocultured with B-CLL cells in vitro. A significant increase in relative numbers of central and effector memory T cells was observed in the CD4 T-cell pool from UM-CLL as compared with M-CLL cases and was associated with high Rai stage, progressive disease and shorter treatment-free survival (TFS). In a multivariate analysis, the relative number of CD4 central and effector memory T cells remained a significant prognostic parameter for TFS after correction for CD38 expression, Ig VH status, genomic aberrations, and Rai stage. The inverse correlation of memory CD4 T cells with TFS might be explained by their potential to support survival of B-CLL cells.

Increased frequency (12%) of circulating chronic lymphocytic leukemia-like B-cell clones in healthy subjects using a highly sensitive multicolor flow cytometry approach

Monoclonal B-cell lymphocytosis (MBL) indicates the presence of less than 5 x 10(9)/L circulating monoclonal B cells in otherwise healthy subjects. Recently, it has been reported that circulating chronic lymphocytic leukemia (CLL)-like B cells can be detected using 4- or 5-multicolor flow cytometry in 5% to 7% of adults with normal lymphocyte counts. We investigated the frequency of circulating monoclonal B cells in 608 healthy subjects older than 40 years with normal blood counts, using a highly sensitive 8-color flow cytometry approach and systematic screening for total PB leukocyte count higher than 5 x 10(6). We show that the frequency of PB monoclonal B cells is markedly higher than previously reported (12% for CLL-like B cells, found at frequencies of 0.17 +/- 0.13 x 10(9) cells/L), the incidence progressively increasing with age. Most cases (62%) showed clonal B-cell levels below the maximum sensitivity of the techniques described by others (< 0.01%), supporting the notion that detection of MBL may largely depend on the sensitivity of the flow cytometry approach used.

The prognosis of clinical monoclonal B cell lymphocytosis differs from prognosis of Rai 0 chronic lymphocytic leukaemia and is recapitulated by biological risk factors

Monoclonal B-cell lymphocytosis (MBL) is an asymptomatic monoclonal expansion of <5.0 x 10(9)/l circulating CLL-phenotype B-cells. The relationship between MBL and Rai 0 CLL, as well as the impact of biological risk factors on MBL prognosis, are unknown. Out of 460 B-cell expansions with CLL-phenotype, 123 clinical MBL (cMBL) were compared to 154 Rai 0 CLL according to clinical and biological profile and outcome. cMBL had better humoral immune capacity and lower infection risk, lower prevalence of del11q22-q23/del17p13 and TP53 mutations, slower lymphocyte doubling time, and longer treatment-free survival. Also, cMBL diagnosis was a protective factor for treatment risk. Despite these favourable features, all cMBL were projected to progress, and lymphocytes <1.2 x 10(9)/l and >3.7 x 10(9)/l were the best thresholds predicting the lowest and highest risk of progression to CLL. Although IGHV status, CD38 and CD49d expression, and fluorescence in situ hybridization (FISH) karyotype individually predicted treatment-free survival, multivariate analysis identified the presence of +12 or del17p13 as the sole independent predictor of treatment requirement in cMBL (Hazard ratio: 5.39, 95% confidence interval 1.98-14.44, P = 0.001). Overall, these data showed that cMBL has a more favourable clinical course than Rai 0 CLL. Given that the biological profile can predict treatment requirement, stratification based on biological prognosticators may be helpful for cMBL management.

Frequency of 5'IGH deletions in B-cell chronic lymphocytic leukemia

In a retrospective analysis of a large group of cases (n=291) with B-cell CLL diagnosis, the various characteristics of IGH aberrations as identified by fluorescence in situ hybridization (FISH) probes were studied. Conventional cytogenetic and FISH studies with the standard panel (13q14, 11q13, 17p13, 12 centromere), and with IGH break-apart probes were done for each case. Abnormal karyotypes were detected with conventional cytogenetics in 29% of cases, and FISH detected abnormalities in 70%. Deletion of 13q14 was the most frequent anomaly, followed by trisomy 12, deletion of 11q, and deletion of 17p. Among the IGH abnormalities detected, translocations with unknown partners (split signals) occurred in only a small group of patients (15%). Instead, deletion of 5'IGH, corresponding to the variable IGH segment (IGH(V)) was the most recurrent aberration, observed in 82% (the second most common finding among our patients). This deletion was associated with good prognostic markers: 13q14 deletion, normal karyotype, and CD38 and ZAP-70 negative expression. Although not exclusive to CLL, the deletion occurred in a high frequency, in contrast to its rarity in other B-cell lymphoproliferative disorders. Longitudinal studies are warranted, to determine when in the disease progression this abnormality is acquired, as a potential early marker, and its impact on the natural history of CLL.

Clinical features and outcome of Chinese patients with monoclonal B-cell lymphocytosis

B-cell chronic lymphocytic leukemia (CLL) is the most common type of adult leukemias in the Western countries, however, infrequent in the Eastern. A diagnosis of CLL requires a count of B-lymphocytes >/=5.0x10(9)/L. Asymptomatic person with <5.0x10(9)/L B-lymphocytes is defined as monoclonal B-cell lymphocytosis (MBL). To compare the clinical characteristics, prognostic factors, and outcome of Chinese patients with MBL and CLL, we present a study from our single centre of 20 patients with MBL and 136 patients with CLL. The factors included: age at diagnosis, gender, direct antiglobulin test (DAT), immunoglobulin heavy chain variable gene (IgHV) mutational status, ZAP-70 protein, CD38 expression level, and molecular cytogenetic aberrations were analyzed in MBL and CLL subgroups. The Kaplan-Meier method was used to construct survival curves, and results were compared using the log-rank test. Patients in the MBL category were slightly older than in the CLL category. There was no significant difference of these clinical and biological characteristics between patients in MBL subgroup and early stage CLL (Binet A). The incidence of positive DAT was significantly increased in CLL patients at Binet B and C, compared with MBL (P=0.036). IgHV gene mutation in MBL is skewed, with more than 92.3% of subjects harbored mutated IgVH genes (P=0.025). The proportion of MBL patients with a 13q14 deletion or trisomy 12 was similar to that of CLL patients. Moreover, markers associated with poor prognosis (deletion of 11q22 or 17p13) in these MBL populations were less than those in Binet B and C CLL patients (P=0.025). No statistically significant differences in ZAP-70 and CD38 status were observed between the MBL and CLL subgroups. During a median follow-up period of 45.5 months, MBL patients had a low probability of progression, with no patients transformed to aggressive non-Hodgkin's lymphoma or dying of CLL-related causes. The overall survival of MBL was very similar to Binet A CLL, but longer than that of CLL patients at advanced stages (Binet B and C) (P=0.024). Our study demonstrated that a more indolent clinical course and superior clinical outcome for patients with MBL compared to CLL.

B-cell clones as early markers for chronic lymphocytic leukemia

BACKGROUND

Otherwise healthy persons with a small number of B-cell clones circulating in the peripheral blood have been designated as having monoclonal B-cell lymphocytosis (MBL). Hospital-based series indicate an excess risk of progression from MBL to chronic lymphocytic leukemia (CLL). In this prospective cohort study, we tested the hypothesis that CLL is always preceded by MBL.

METHODS

Among 77,469 healthy adults who were enrolled in the nationwide, population-based Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, we identified 45 subjects in whom CLL was subsequently diagnosed (up to 6.4 years later) through the collection of a peripheral-blood sample. Using six-color flow cytometry (with antibodies CD45, CD19, CD5, CD10, kappa, and lambda) and immunoglobulin heavy-chain gene rearrangement by reverse-transcriptase-polymerase-chain-reaction assay, we determined the association between MBL and subsequent CLL and characterized the immunoglobulin gene repertoire of the prediagnostic B-cell clones.

RESULTS

On the basis of either flow-cytometric or molecular analysis, 44 of 45 patients with CLL (98%; 95% confidence interval [CI], 88 to 100) had a prediagnostic B-cell clone; in 41 patients (91%; 95% CI, 79 to 98), the presence of the B-cell clone was confirmed by both methods. The presence of immunoglobulin heavy-chain variable (IGHV) genes was determined in 35 of 45 prediagnostic clones (78%). Of these clones, 16 (46%) were IGHV3 subgroup genes (including 6 [17%] IGHV3-23 genes) and 9 (26%) were IGHV4 subgroup genes (including 4 [11%] IGHV4-34 genes). Furthermore, 27 of 35 of the IGHV sequences (77%) had mutations, with similar distributions after stratification either below or above the median time between the collection of the prediagnostic blood sample and the subsequent CLL diagnosis.

CONCLUSIONS

In peripheral blood obtained up to 77 months before a CLL diagnosis, prediagnostic B-cell clones were present in 44 of 45 patients with CLL.

The 2008 WHO classification of lymphomas: implications for clinical practice and translational research

The 4(th) edition of the WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues published in 2008 builds upon the success of the 2001 3(rd) edition; new entities are defined, and solutions for problematic categories are sought. Recent studies have drawn attention to the biological overlap between classical Hodgkin lymphoma (CHL) and diffuse large B-cell lymphomas (DLBCL). Similarly, there is a greater appreciation of the borderlands between Burkitt lymphoma and DLBCL. Strategies for the management of these borderline lesions are proposed. Additionally, age-specific and site-specific factors play an important role in the definition of several new entities, which also have biological underpinnings. Among the peripheral T-cell lymphomas (PTCL), more precise definitions were introduced for several entities, including anaplastic large cell lymphoma, angioimmunoblastic T-cell lymphoma, enteropathy-associated T-cell lymphoma, and subcutaneous panniculitis-like T-cell lymphoma. Several new variants of primary cutaneous T-cell lymphomas are proposed. Finally, the subclassification and categorization of the most common lymphoma subtypes, follicular lymphoma (FL) and DLBCL, were altered to enhance diagnostic accuracy and aid in clinical management. The 2008 WHO classification also draws attention to early events in lymphomagenesis. These lesions help delineate the earliest steps in neoplastic transformation and generally mandate a conservative therapeutic approach. The 2001 classification was rapidly adopted for clinical trials and successfully served as a common language for scientists comparing genetic and functional data. The modifications made in the 2008 classification are the result of this successful partnership among pathologists, clinicians, and biologists, but are only a stepping stone to the future.

Monoclonal B-cell lymphocytosis

The incidence and presenting features of chronic lymphocytic leukemia (CLL) have changed significantly over the last century. Routine diagnostic techniques can now detect very low levels of CLL phenotype cells. Monoclonal B-cell lymphocytosis (MBL) is a relatively recent diagnostic category encapsulating individuals with an abnormal B-cell population but not meeting the diagnostic criteria for a B-cell malignancy. This review focuses on CLL-type MBL, which represents the majority of MBL cases identified in diagnostic laboratories. CLL-type MBL has a phenotype identical to CLL and shares the same chromosomal abnormalities even at the lowest levels detectable. Recent evidence suggests that the immunoglobulin gene usage plays a key role in whether the abnormal cells will develop in significant numbers. In most cases, CLL-type MBL is a stable condition with only 1% per year among those presenting for clinical attention developing progressive disease requiring treatment, although suppressed immune function may have a more significant impact on outcome.

The 2008 WHO classification of lymphomas: implications for clinical practice and translational research

The 4th edition of the WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues published in 2008 builds upon the success of the 2001 3rd edition; new entities are defined, and solutions for problematic categories are sought. Recent studies have drawn attention to the biological overlap between classical Hodgkin lymphoma (CHL) and diffuse large B-cell lymphomas (DLBCL). Similarly, there is a greater appreciation of the borderlands between Burkitt lymphoma and DLBCL. Strategies for the management of these borderline lesions are proposed. Additionally, age-specific and site-specific factors play an important role in the definition of several new entities, which also have biological underpinnings. Among the peripheral T-cell lymphomas (PTCL), more precise definitions were introduced for several entities, including anaplastic large cell lymphoma, angioimmunoblastic T-cell lymphoma, enteropathy-associated T-cell lymphoma, and subcutaneous panniculitis-like T-cell lymphoma. Several new variants of primary cutaneous T-cell lymphomas are proposed. Finally, the subclassification and categorization of the most common lymphoma subtypes, follicular lymphoma (FL) and DLBCL, were altered to enhance diagnostic accuracy and aid in clinical management. The 2008 WHO classification also draws attention to early events in lymphomagenesis. These lesions help delineate the earliest steps in neoplastic transformation and generally mandate a conservative therapeutic approach. The 2001 classification was rapidly adopted for clinical trials and successfully served as a common language for scientists comparing genetic and functional data. The modifications made in the 2008 classification are the result of this successful partnership among pathologists, clinicians, and biologists, but are only a stepping stone to the future.

The immunoglobulin gene repertoire of low-count chronic lymphocytic leukemia (CLL)-like monoclonal B lymphocytosis is different from CLL: diagnostic implications for clinical monitoring

In the revised National Cancer Institute Working Group (NCI-WG)/International Workshop on Chronic Lymphocytic Leukemia (IWCLL) guidelines for CLL, CLL-like monoclonal B lymphocytosis (MBL) is defined as the presence of less than 5 x 10(9)/L B lymphocytes in the peripheral blood. However, the concentration of MBL in the blood is extremely variable. MBL in subjects with lymphocytosis require treatment at a rate of 1.1% per year and present immunoglobulin (IG) gene features and similar to good prognosis CLL. Little is known about low-count MBL cases, accidentally found in the general population. We analyzed IGHV-D-J rearrangements in 51 CLL-like MBL cases from healthy individuals, characterized by few clonal B cells. Seventy percent of the IGHV genes were mutated. The most frequent IGHV gene was IGHV4-59/61, rarely used in CLL, whereas the IGHV1-69 gene was lacking and the IGHV4-34 gene was infrequent. Only 2 of 51 (3.9%) MBL cases expressed a CLL-specific stereotyped HCDR3. Therefore, the IG gene repertoire in low-count MBL differs from both mutated and unmutated CLL, suggesting that the detection of MBL in an otherwise healthy subject is not always equivalent to a preleukemic state. Detailed IG analysis of individual MBL may help to identify cases that necessitate continuous clinical monitoring to anticipate disease progression.

B-cell count and survival: differentiating chronic lymphocytic leukemia from monoclonal B-cell lymphocytosis based on clinical outcome

The diagnosis of chronic lymphocytic leukemia (CLL) in asymptomatic patients has historically been based on documenting a characteristic lymphocyte clone and the presence of lymphocytosis. There are minimal data regarding which lymphocyte parameter (absolute lymphocyte count [ALC] or B-cell count) and what threshold should be used for diagnosis. We analyzed the relationship of ALC and B-cell count with clinical outcome in 459 patients with a clonal population of CLL phenotype to determine (1) whether the CLL diagnosis should be based on ALC or B-cell count, (2) what lymphocyte threshold should be used for diagnosis, and (3) whether any lymphocyte count has independent prognostic value after accounting for biologic/molecular prognostic markers. B-cell count and ALC had similar value for predicting treatment-free survival (TFS) and overall survival as continuous variables, but as binary factors, a B-cell threshold of 11 x 10(9)/L best predicted survival. B-cell count remained an independent predictor of TFS after controlling for ZAP-70, IGHV, CD38, or fluorescence in situ hybridization (FISH) results (all P < .001). These analyses support basing the diagnosis of CLL on B-cell count and retaining the size of the B-cell count in the diagnostic criteria. Using clinically relevant criteria to distinguish between monoclonal B-cell lymphocytosis (MBL) and CLL could minimize patient distress caused by labeling asymptomatic people at low risk for adverse clinical consequences as having CLL.

Monoclonal B-cell lymphocytosis and chronic lymphocytic leukemia

BACKGROUND

A diagnosis of chronic lymphocytic leukemia (CLL) requires a count of over 5000 circulating CLL-phenotype cells per cubic millimeter. Asymptomatic persons with fewer CLL-phenotype cells have monoclonal B-cell lymphocytosis (MBL). The goal of this study was to investigate the relation between MBL and CLL.

METHODS

We investigated 1520 subjects who were 62 to 80 years of age with a normal blood count and 2228 subjects with lymphocytosis (>4000 lymphocytes per cubic millimeter) for the presence of MBL, using flow cytometry. Monoclonal B cells were further characterized by means of cytogenetic and molecular analyses. A representative cohort of 185 subjects with CLL-phenotype MBL and lymphocytosis were monitored for a median of 6.7 years (range, 0.2 to 11.8).

RESULTS

Monoclonal CLL-phenotype B cells were detected in 5.1% of subjects (78 of 1520) with a normal blood count and 13.9% (309 of 2228) with lymphocytosis. CLL-phenotype MBL had a frequency of 13q14 deletion and trisomy 12 similar to that of CLL and showed a skewed repertoire of the immunoglobulin heavy variable group (IGHV) genes. Among 185 subjects presenting with lymphocytosis, progressive lymphocytosis occurred in 51 (28%), progressive CLL developed in 28 (15%), and chemotherapy was required in 13 (7%). The absolute B-cell count was the only independent prognostic factor associated with progressive lymphocytosis. During follow-up over a median of 6.7 years, 34% of subjects (62 of 185) died, but only 4 of these deaths were due to CLL. Age above 68 years and hemoglobin level below 12.5 g per deciliter were the only independent prognostic factors for death.

CONCLUSIONS

The CLL-phenotype cells found in the general population and in subjects with lymphocytosis have features in common with CLL cells. CLL requiring treatment develops in subjects with CLL-phenotype MBL and with lymphocytosis at the rate of 1.1% per year.

Novel insights in chronic lymphocytic leukemia: are we getting closer to understanding the pathogenesis of the disease?

Chronic lymphocytic leukemia (CLL) has unique epidemiologic, biologic, and clinical features. The progressively emerging picture leads us to consider that the critical genes for malignant CLL cells are those regulated by a number of microRNAs revealed by refined cytogenetic and molecular studies, and that the key molecule is the B-cell receptor (BCR). The hypothesis that CLL cells might be selected by some sort of antigenic pressure is strengthened by numerous findings indicating that a BCR-mediated stimulation plays a relevant role in the natural history of the disease and that autoantigens, as well as molecular structures instrumental in eliminating and scavenging apoptotic cells and pathogenic bacteria, may be relevant in triggering and/or facilitating the evolution of CLL. An important question is whether the tiny monoclonal B-cell populations phenotypically similar to CLL (that occur in the peripheral blood of about 3.5% of healthy individuals and are termed monoclonal B lymphocytosis) might be a critical step in the development of CLL. All relevant events of CLL occur in tissues in which a number of cellular and molecular interactions shape a microenvironment conducive to the accumulation of malignant cells and favor the organization of proliferating cells in focal aggregates of variable size that form the pseudofollicular proliferation centers. Given the impact that understanding the pathogenesis of CLL might have on the development of new treatments, the purposes of this review are to discuss whether the novel insights in CLL are leading us closer to understanding the tenet of the disease; to define the emerging new, stimulating questions; and to unfold the major challenges that still need to be addressed.