Immunophenotypic analysis reveals heterogeneity and common biologic aspects in monoclonal B-cell lymphocytosis

The Cytogenetic Profile of Primary and Secondary Plasma Cell Leukemia: Etiopathogenetic Perspectives, Prognostic Impact and Clinical Relevance to Newly Diagnosed Multiple Myeloma with Differential Circulating Clonal Plasma Cells

Plasma cell leukemia (PCL) is a rare and aggressive plasma cell dyscrasia that may appear as de-novo leukemia (pPCL) or on the basis of a pre-existing multiple myeloma (MM), called secondary plasma cell leukemia (sPCL). In this prospective study, we have applied a broad panel of FISH probes in 965 newly diagnosed MM (NDMM) and 44 PCL cases of both types to reveal the particular cytogenetic differences among the three plasma cell dyscrasias. In order to evaluate the frequency and patterns of clonal evolution, the same FISH panel was applied both at diagnosis and at the time of first relapse for 81 relapsed MM patients and both at MM diagnosis and during sPCL transformation for the 19 sPCL cases described here. pPCL was characterized by frequent MYC translocations and t(11;14) with a 11q13 breakpoint centered on the MYEOV gene, not commonly seen in MM. sPCL had a higher number of FISH abnormalities and was strongly associated with the presence of del(17p13), either acquired at the initial MM stage or as a newly acquired lesion upon leukemogenesis in the context of the apparent clonal evolution observed in sPCL. In clinical terms, sPCL showed a shorter overall survival than pPCL with either standard or high-risk (t(4;14) and/or t(14;16) and/or del(17p13) and/or ≥3 concomitant aberrations) abnormalities (median 5 months vs. 21 and 11 months respectively, p < 0.001), suggesting a prognostic stratification based on cytogenetic background. These observations proved relevant in the NDMM setting, where higher levels of circulating plasma cells (CPCs) were strongly associated with high-risk cytogenetics (median frequency of CPCs: 0.11% of peripheral blood nucleated cells for high-risk vs. 0.007% for standard-risk NDMM, p < 0.0001). Most importantly, the combined evaluation of CPCs (higher or lower than a cut-off of 0.03%), together with patients’ cytogenetic status, could be used for an improved prognostic stratification of NDMM patients.

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.

Fish evaluation of additional cytogenetic aberrations and hyperdiploidy in childhood Burkitt lymphoma

Beyond MYC rearrangement, Burkitt lymphoma (BL) often presents with additional aberrations. Biopsy touch imprints from 72 children with BL were tested with interphase fluorescence in-situ hybridization (i-FISH) for MYC, BCL2, BCL6, IGH, IGK and IGL rearrangements and copy-number aberrations involving 1q21/1p32, 7cen/7q31, 9cen/9p21, 13q14/13q34 and 17cen/17p13. Diploid status deviations were investigated with chromosome enumeration probes. MYC rearrangement was demonstrated in all cases. Additional aberrations included +1q (21/72:29.2%), +7q (14/72:19.4%), 13q- (14/72:19.4%), 9p-(6/72:8.3%) and hyperdiploidy (6/72:8.3%). Advanced clinical stage IV, +7q and 9p- were associated with shorter overall survival, with stage IV and +7q retaining prognostic significance on multivariate analysis. No relapse or death was reported among the hyperdiploid cases. This i-FISH investigation provides information on the genetic profile of BL and may prove valuable for patients with no karyotype analysis. Demonstration of hyperdiploidy could evolve research on clonal evolution pathways and probably identify a subgroup of children with favorable prognosis.

Deep Phenotyping Reveals Distinct Immune Signatures Correlating with Prognostication, Treatment Responses, and MRD Status in Multiple Myeloma

Simple Summary

In Multiple Myeloma (MM) malignant cells accumulate in the bone marrow (BM), where they interact with various cell populations. These complex interactions impose mechanisms of tumor growth and proliferation, immune surveillance and immune evasion. The aim of the present study was a detailed immune characterization of MM during the course of the disease, in order to highlight signatures which are clinically relevant. Analyses of both BM and peripheral blood (PB) in matched patients’ samples, we showed that PB cannot representatively reflect the BM microenvironment. Particular immune signatures in BM and PB significantly correlated with established prognostic features and could independently associate with distinct responses to the same induction therapy. Moreover, our data provide evidence of a diverse immune profile according to patients’ MRD status post treatment. Finally, we provide insights that unique PB immune profiles may be used for the prediction of MRD status through a simple non-invasive approach.

Abstract

Despite recent advances, Multiple Myeloma (MM) remains an incurable disease with apparent heterogeneity that may explain patients’ variable clinical outcomes. While the phenotypic, (epi)genetic, and molecular characteristics of myeloma cells have been thoroughly examined, there is limited information regarding the role of the bone marrow (BM) microenvironment in the natural history of the disease. In the present study, we performed deep phenotyping of 32 distinct immune cell subsets in a cohort of 94 MM patients to reveal unique immune profiles in both BM and peripheral blood (PB) that characterize distinct prognostic groups, responses to induction treatment, and minimal residual disease (MRD) status. Our data show that PB cells do not reflect the BM microenvironment and that the two sites should be studied independently. Adverse ISS stage and high-risk cytogenetics were correlated with distinct immune profiles; most importantly, BM signatures comprised decreased tumor-associated macrophages (TAMs) and erythroblasts, whereas the unique Treg signatures in PB could discriminate those patients achieving complete remission after VRd induction therapy. Moreover, MRD negative status was correlated with a more experienced CD4- and CD8-mediated immunity phenotype in both BM and PB, thus highlighting a critical role of by-stander cells linked to MRD biology.

Lymphoma-like monoclonal B cell lymphocytosis in a patient population: biology, natural evolution, and differences from CLL-like clones

High-count monoclonal B cell lymphocytosis (MBL) with a chronic lymphocytic leukemia (CLL) phenotype is a well-known entity, featuring 1-4% annual risk of progression towards CLL requiring treatment. Lymphoma-like MBL (L-MBL), on the other hand, remains poorly defined and data regarding outcome are lacking. We retrospectively evaluated 33 L-MBL cases within our hospital population and compared them to 95 subjects with CLL-like MBL (C-MBL). Diagnoses of L-MBL were based on asymptomatic B cell clones with Matutes score < 3, B cells < 5.0 × 10³/μl, and negative computerized tomography scans. We found that median B cell counts were considerably lower compared to C-MBL (0.6 vs 2.3 × 10³/μl) and remained stable over time. Based on immunophenotyping and immunogenetic profiling, most L-MBL clones did not correspond to known lymphoma entities. A strikingly high occurrence of paraproteinemia (48%), hypogammaglobulinemia (45%), and biclonality (21%) was seen; these incidences being significantly higher than in C-MBL (17, 21, and 5%, respectively). Unrelated monoclonal gammopathy of undetermined significance was a frequent feature, as the light chain type of 5/12 paraproteins detected was different from the clonal surface immunoglobulin. After 46-month median follow-up, 2/24 patients (8%) had progressed towards indolent lymphoma requiring no treatment. In contrast, 41% of C-MBL cases evolved to CLL and 17% required treatment. We conclude that clinical L-MBL is characterized by pronounced immune dysregulation and very slow or absent progression, clearly separating it from its CLL-like counterpart.

Expression of CD43 in chronic lymphoproliferative leukemias

BACKGROUND

CD43 has been used on histological samples for the differential diagnosis of lymphoproliferative disorders but there is scarce data on its use by flow cytometry (FC). We set out to characterize the expression of CD43 by FC in B-cell lymphoproliferative disorders and to determine its possible role in the differential diagnosis of these malignancies.

METHODS

We analyzed the expression of CD43 in clonal B-cell lymphoproliferative disorders with exclusive peripheral blood and/or bone marrow involvement based on their Moreau chronic lymphocytic leukemia (CLL) score with particular emphasis on Moreau CLL score 3 (MS3) cases, which often present a diagnostic challenge. The cohort included 433 CLL (score 4-5), 34 MS3 and 166 lymphoproliferative disorders with lower scores.

RESULTS

Generally, the higher the Moreau CLL score, the higher CD43-positivity (425/443 [96%] for CLL, 23/34 [67%] for MS3 and 18/166 [11%] for cases with lower scores). MS3 cases constituted 5.4% of all cases and were more frequently CD5, CD200, CD43-positive and had del(q13) than score 0-2 cases. Among MS3 cases, del(13q) cases were predominantly CD43-positive (12/13).

CONCLUSIONS

The frequency of CD43-positivity increases sharply with the Moreau score. MS3 cases seem to include both CLL and non-CLL lymphoproliferative disorders and CD43 could aid in the differential diagnosis between the two. However, studies analyzing the correlation between CD43 expression and the underlying biologic changes of these cases are warranted. © 2017 International Clinical Cytometry Society.

Issues in diagnosis of small B cell lymphoid neoplasms involving the bone marrow and peripheral blood. Report on the Bone Marrow Workshop of the XVIIth meeting of the European Association for Haematopathology and the Society for Hematopathology

Small B cell lymphoid neoplasms are the most common lymphoproliferative disorders involving peripheral blood (PB) and bone marrow (BM). The Bone Marrow Workshop (BMW) organized by the European Bone Marrow Working Group (EBMWG) of the European Association for Haematopathology (EAHP) during the XVIIth EAHP Meeting in Istanbul, October 2014, was dedicated to discussion of cases illustrating how the recent advances in immunophenotyping, molecular techniques and cytogenetics provide better understanding and classification of these entities. Submitted cases were grouped into following categories: (i) cases illustrating diagnostic difficulties in chronic lymphocytic leukaemia (CLL); (ii) cases of BM manifestations of small B cell lymphoid neoplasms other than CLL; (iii) transformation of small B cell lymphoid neoplasms in the BM; and (iv) multiclonality and composite lymphomas in the BM. This report summarizes presented cases and conclusions of the BMW and provides practical recommendations for classification of the BM manifestations of small B cell lymphoid neoplasms based on the current state of knowledge.

Successful Treatment of Leukemic Mature B-Cell Lymphoid Neoplasm with Similar Features to Splenic Marginal Zone Lymphoma Possessing Aberrant Myeloid Markers

In splenic marginal zone lymphoma (SMZL), there are cases that cannot accurately be classified as such because of overlapping morphologic and/or immunophenotypic features. We report here a 76-year-old Japanese female, who showed leukemic B-cell lymphoproliferative disease possessing characteristic features identified for SMZL. The patient was leukemic with white blood cell counts 49,400/µL (abnormal cells, 78.5%) and neoplastic cells were characterized by aberrant expression of myeloid markers with CD19⁺CD13⁺ (64.2%) and CD20⁺CD11c⁺ (25.1%). Considering her history of previous chemotherapy and systemic leukemic phase of the disease, we treated the patient without performing splenectomy, with successful use of a combination of rituximab/bendamustine hydrochloride and of rituximab/cladribine. The patient has been in a complete remission longer than 44 months, with no detectable M-protein.