Genetic background and evolution of relapses in aggressive B-cell lymphomas

Mutational heterogeneity in large B-cell lymphoma: insights from paired biopsies

INTRODUCTION

Large B-cell lymphoma (LBCL) exhibits striking clinical and molecular heterogeneity. New approaches have emerged to explore tumor heterogeneity and classify LBCL into biological categories. Consequently, the informational requirements from diagnostic samples to provide the necessary information have increased, but the adequacy of single-site biopsies to provide such information is largely unknown. Here we describe spatial and temporal intra-patient variations in the mutational landscape of paired biopsies.

METHODS

Paired biopsies from 30 patients with LBCL were obtained from spatially distinct sites at the time of primary diagnosis before treatment and/or at a subsequent relapse. The samples were sequenced using a custom designed 59-gene next generation sequencing (NGS) lymphoma panel.

RESULTS

Differences in detected mutations of pathogenic or likely pathogenic significance were frequent both when comparing paired diagnostic biopsies, 2/6 (33%), and when comparing paired biopsies at primary diagnosis and relapse, 8/16 (50%). Mutational heterogeneity tended to increase with longer time interval between biopsies. Analysis of paired diagnostic and relapse biopsies revealed that certain clones present at diagnosis disappeared, while new clones emerged at relapse. Notably, TP53 mutations were detected in six out of seven patients in an extranodal location. In two cases, TP53 mutation was only detected in the relapse biopsy. Several of the mutations identified in this study are used or under investigation as targets for cancer treatments.

CONCLUSION

Multi-site biopsies revealed spatial and temporal mutational heterogeneity in patients with LBCL. Our findings indicate that mutational differences between biopsy pairs can occur at all timepoints examined. This underscores the necessity of performing repeat biopsies with each relapse to capture the full spectrum of genetic aberrations.

Optimization and characterization of Rituximab targeted multidrug loaded cyclodextrin nanoparticles against Non-Hodgkin Lymphoma

Currently, Non-Hodgkin Lymphoma (NHL) constitutes 85-90 % of all lymphomas. Clinical treatment of NHL is based on the "4-drug regimen" known as CHOP (cyclophosphamide, doxorubicin, vincristine, prednisone). Rituximab (RTX) is added to increase the effectiveness and selectivity of the treatment and is the first-line standard treatment for NHL patients. However, success is often prevented by the development of drug resistance. In this study, it was aimed to overcome drug resistance by using two novel tumor-targeted derivatives: guanidine-amphiphilic cyclodextrin (ACD) and guanidine-cyclodextrin polymer (PCD) nanoparticles (NP). These constructs display promise in overcoming drug resistance and enhancing the effectiveness of R-CHOP treatment while potentially eliminating the need for corticosteroid. NP were found to be smaller than 200 nm by dynamic light scattering (DLS). Hemolytic activity and cytotoxicity data on L929 cells demonstrated the safety of the newly synthesized CD derivatives. Additional in vitro characterization studies, including surface charge, physical stability, drug loading capacity, drug release profile, and imaging, as well as conventional and 3D cell culture studies were carried out. Compared to drug solutions, the viability of Daudi human lymphoma cells was statistically significantly decreased in both drug-loaded ACD and PCD NP formulations (p < 0.05). Additionally, RTX-conjugated and drug-loaded ACD NPs exhibited the lowest cell viability due to RTX dependent cytotoxicity.

Applications of Multimodal Artificial Intelligence in Non-Hodgkin Lymphoma B Cells

Given advancements in large-scale data and AI, integrating multimodal artificial intelligence into cancer research can enhance our understanding of tumor behavior by simultaneously processing diverse biomedical data types. In this review, we explore the potential of multimodal AI in comprehending B-cell non-Hodgkin lymphomas (B-NHLs). B-cell non-Hodgkin lymphomas (B-NHLs) represent a particular challenge in oncology due to tumor heterogeneity and the intricate ecosystem in which tumors develop. These complexities complicate diagnosis, prognosis, and therapy response, emphasizing the need to use sophisticated approaches to enhance personalized treatment strategies for better patient outcomes. Therefore, multimodal AI can be leveraged to synthesize critical information from available biomedical data such as clinical record, imaging, pathology and omics data, to picture the whole tumor. In this review, we first define various types of modalities, multimodal AI frameworks, and several applications in precision medicine. Then, we provide several examples of its usage in B-NHLs, for analyzing the complexity of the ecosystem, identifying immune biomarkers, optimizing therapy strategy, and its clinical applications. Lastly, we address the limitations and future directions of multimodal AI, highlighting the need to overcome these challenges for better clinical practice and application in healthcare.

Fifth Edition of the World Health Classification of Tumors of the Hematopoietic and Lymphoid Tissues: B-cell Neoplasms

We review B-cell neoplasms in the 5th edition of the World Health Organization classification of hematolymphoid tumors (WHO-HEM5). The revised classification is based on a multidisciplinary approach including input from pathologists, clinicians, and other experts. The WHO-HEM5 follows a hierarchical structure allowing the use of family (class)-level definitions when defining diagnostic criteria are partially met or a complete investigational workup is not possible. Disease types and subtypes have expanded compared with the WHO revised 4th edition (WHO-HEM4R), mainly because of the expansion in genomic knowledge of these diseases. In this review, we focus on highlighting changes and updates in the classification of B-cell lymphomas, providing a comparison with WHO-HEM4R, and offering guidance on how the new classification can be applied to the diagnosis of B-cell lymphomas in routine practice.

Detection of Second Primary Lymphoma in Late Diffuse Large B-cell Lymphoma Recurrences

Approximately one-third of patients with diffuse large B-cell lymphoma (DLBCL) relapse and often require salvage chemotherapy followed by autologous stem cell transplantation. In most cases, the clonal relationship between the first diagnosis and subsequent relapse is not assessed, thereby potentially missing the identification of second primary lymphoma. In this study, the clonal relationship of 59 paired DLBCL diagnoses and recurrences was established by next-generation sequencing-based detection of immunoglobulin gene rearrangements. Among 50 patients with interpretable results, 43 patients (86%) developed clonally related relapsed disease. This was observed in 100% of early recurrences (<2 years), 80% of the recurrences with an interval between 2 and 5 years, and 73% of late recurrences (≥5 years). On the other hand, 7 (14%) out of 50 patients displayed different dominant clonotypes in primary DLBCL and clinical recurrences, confirming the occurrence of second primary DLBCL; 37% of DLBCL recurrences that occurred ≥4 years after diagnosis were shown to be second primary lymphomas. The clonally unrelated cases were Epstein-Barr virus positive in 43% of the cases, whereas this was only 5% in the relapsed DLBCL cases. In conclusion, next-generation sequencing-based clonality testing in late recurrences should be considered in routine diagnostics to distinguish relapse from second primary lymphoma, as this latter group of patients with DLBCL may benefit from less-intensive treatment strategies.

A bibliometric analysis of diffuse large B-cell lymphoma research from 2001 to 2020

Diffuse large B-cell lymphoma (DLBCL) is a subtype of non-Hodgkin lymphoma (NHL) with the highest incidence, accounting for approximately one-third of NHL cases. Given the accumulated scientific publications related to the DLBCL domain, this study aimed to provide a comprehensive review of DLBCL studies from this millennium using the bibliometric method. With a strict retrieval strategy applied in the Web of Science database, a total of 10,869 publications from 2001 to 2020 were obtained and exported. The temporal and geographical distribution of these publications and the performance of contributing countries, institutions, journals, and authors corresponding to these documents were investigated, as well as an in-depth content analysis through keyword co-occurrence. With regard to the most productive countries, the United States ranks first with 2344 (21.6%) publications and shows the most frequent collaborations with other countries. By contrast, China has demonstrated remarkable performance in the growth rate of publications over the years, and it ranks first in the number of publications in the last five years. The University of Texas System is the institution with the highest number of published articles (4.99%). Leukemia Lymphoma is the journal with the highest number of publications in this field which contributed 588 articles. Solid and close collaborations between scholars are becoming more frequent over the four five-year periods. Overall, the highest cooperation frequency in the last two decades happens to Gascoyne RD at the British Columbia Cancer Agency and British Columbia Cancer Research Center in Canada. By comparing the article citation and keyword co-occurrence in each five-year period, as well as the changes in keyword clusters over two decades, we conclude that the stage, evaluation, prognosis, and treatment of DLBCL have always been the research hotspots in this field. Meanwhile, the evolution of keyword co-occurrence over the years demonstrates that new clusters appear. For instance, the effect of ferroptosis mechanism in DLBCL, immunotherapy for DLBCL, and PDL-1, PDL-2, and CAR-T therapy have drawn increasing attention from academia. Our research highlights the key characteristics of DLBCL research and provides comprehensive insights into the research status and evolutions in this field.

Tumor mutation burden estimated by a 69-gene-panel is associated with overall survival in patients with diffuse large B-cell lymphoma

BACKGROUND

Tumor mutation burden (TMB) as estimated by cancer gene panels (CGPs) has been confirmed to be associated with prognosis and is effective in predicting clinical benefit from immune checkpoint blockade (ICB) in solid tumors. However, whether the TMB calculated by CGPs is associated with overall survival (OS) for patients with diffuse large B-cell lymphoma (DLBCL) is worth exploring.

METHODS

The prognostic value of panel-TMB, calculated by a panel of 69 genes (GP69), for 87 DLBCL patients in our clinical center (GDPH dataset) was explored. The results were further validated using 37 DLBCL patients from the Cancer Genome Atlas (TCGA) database (TCGA dataset).

RESULTS

Spearman correlation analysis suggested that panel-TMB is positively correlated with the TMB calculated by whole-exome sequencing (wTMB) in the TCGA dataset (R = 0.76, P < 0.0001). Both GDPH and TCGA results demonstrated that higher panel-TMB is significantly associated with a poor OS for DLBCL patients (P < 0.05) where a panel of 13 genes was associated with poor OS, and another panel of 26 genes was correlated with a favorable OS for DLBCL patients. Further subgroup analysis indicated that higher panel-TMB had shorter OS in DLBCL patients with younger than 60 years, elevated LDH, greater than one extranodal involvement, stage III/IV, an IPI score of 3-5, or HBsAg, anti-HBc, or HBV-DNA negativity (P < 0.05). Interestingly, the nomogram model constructed by panel-TMB, stage, and IPI could individually and visually predict the 1-, 2- and 3-year OS rates of DLBCL patients.

CONCLUSIONS

We established GP69 for the evaluation of OS for Chinese DLBCL patients. panel-TMB might be a potential predictor for prognostic stratification of DLBCL patients.

Second malignant neoplasms after treatment of non-Hodgkin's lymphoma-a retrospective multinational study of 189 children and adolescents

Data on the spectrum of second malignant neoplasms (SMNs) after primary childhood non-Hodgkin's lymphoma (NHL) are scarce. One-hundred-and-eighty-nine NHL patients diagnosed in a 30 years period of 1980-2010 developing an SMN were retrieved from 19 members of the European Intergroup for Childhood NHL and/or the international Berlin-Frankfurt-Münster Study Group. Five subgroups of SMNs were identified: (1) myeloid neoplasms (n = 43; 23%), (2) lymphoid neoplasms (n = 51; 27%), (3) carcinomas (n = 48; 25%), (4) central nervous system (CNS) tumors (n = 19; 10%), and (5) "other" SMNs (n = 28; 15%). In 37 patients (20%) preexisting disorders were reported with 90% having any kind of cancer predisposition syndrome (CPS). For the 189 primary NHL patients, 5-year overall survival (OS) after diagnosis of an SMN was 56 ± 4%, being worst for patients with preexisting disorders at 28 ± 8%. Five-year OS rates were 38 ± 8%, 59 ± 7%, 79 ± 8%, 34 ± 12%, and 62 ± 11%, respectively, for patients with myeloid and lymphoid neoplasms, carcinomas, CNS tumors, and "other" SMNs (p < 0.0001). Patients with SMNs after childhood NHL having a reported CPS, mostly mismatch repair disorders, carried a very poor prognosis. Moreover, although outcome was favorable in some subtypes of SMNs after childhood NHL (carcinomas, lymphoid neoplasms), other SMNs such as myeloid neoplasms and CNS tumors had a dismal prognosis.

Molecular Genetics of Relapsed Diffuse Large B-Cell Lymphoma: Insight into Mechanisms of Therapy Resistance

The majority of patients with diffuse large B-cell lymphoma (DLBCL) can be treated successfully with a combination of chemotherapy and the monoclonal anti-CD20 antibody rituximab. Nonetheless, approximately one-third of the patients with DLBCL still experience relapse or refractory (R/R) disease after first-line immunochemotherapy. Whole-exome sequencing on large cohorts of primary DLBCL has revealed the mutational landscape of DLBCL, which has provided a framework to define novel prognostic subtypes in DLBCL. Several studies have investigated the genetic alterations specifically associated with R/R DLBCL, thereby uncovering molecular pathways linked to therapy resistance. Here, we summarize the current state of knowledge regarding the genetic alterations that are enriched in R/R DLBCL, and the corresponding pathways affected by these gene mutations. Furthermore, we elaborate on their potential role in mediating therapy resistance, also in connection with findings in other B-cell malignancies, and discuss alternative treatment options. Hence, this review provides a comprehensive overview on the gene lesions and molecular mechanisms underlying R/R DLBCL, which are considered valuable parameters to guide treatment.

Extranodal site of diffuse large B-cell lymphoma and the risk of R-CHOP chemotherapy resistance and early relapse

BACKGROUND

About 20%-30% of diffuse large B-cell lymphoma (DLBCL) patients experience early disease progression despite R-CHOP chemotherapy treatment. Revised international prognostic index (R-IPI) score could risk stratify DLBCL patients but does not identify exactly which patient will be resistant to R-CHOP therapy or experience early relapse.

AIMS OF THE STUDY

To analyse pre-treatment clinical features of DLBCL patients that are predictive of R-CHOP therapy resistance and early disease relapse after R-CHOP therapy treatment.

METHODS USED TO CONDUCT THE STUDY

A total of 698 lymphoma patients were screened and 134 R-CHOP-treated DLBCL patients were included. The Lugano 2014 criteria was applied for assessment of treatment response. DLBCL patients were divided into R-CHOP resistance/early relapse group and R-CHOP sensitive/late relapse group.

RESULTS OF THE STUDY

81 of 134 (60%) were R-CHOP sensitive/late relapse, while 53 (40%) were R-CHOP resistance/early relapse. The median follow-up period was 59 months ± standard error 3.6. Five-year overall survival rate of R-CHOP resistance/early relapse group was 2.1%, while it was 89% for RCHOP sensitive/late relapse group. Having more than one extranodal site of DLBCL disease is an independent risk factor for R-CHOP resistance/early relapse [odds ratio = 5.268 (1.888-14.702), P = .002]. The commonest extranodal sites were head and neck, gastrointestinal tract, respiratory system, vertebra and bones. Advanced age (>60 years), advanced disease stage (lll-lV), raised pre-treatment lactate dehydrogenase level, bone marrow involvement of DLBCL disease high Eastern Cooperative Oncology Group status (2-4) and high R-IPI score (3-5) showed no significant association with R-CHOP therapy resistance/early disease relapse (multivariate analysis: P > .05).

CONCLUSION AND CLINICAL IMPLICATIONS

DLBCL patients with more than one extranodal site are 5.268 times more likely to be R-CHOP therapy resistance or experience early disease relapse after R-CHOP therapy. Therefore, correlative studies are warranted in DLBCL patients with more than one extranodal site of disease to explore possible underlying mechanisms of chemoresistance.

Role of the Transcription Factor Yin Yang 1 and Its Selectively Identified Target Survivin in High-Grade B-Cells Non-Hodgkin Lymphomas: Potential Diagnostic and Therapeutic Targets

B-cell non-Hodgkin lymphomas (B-NHLs) are often characterized by the development of resistance to chemotherapeutic drugs and/or relapse. During drug-induced apoptosis, Yin Yang 1 (YY1) transcription factor might modulate the expression of apoptotic regulators genes. The present study was aimed to: (1) examine the potential oncogenic role of YY1 in reversing drug resistance in B-NHLs; and (2) identify YY1 transcriptional target(s) that regulate the apoptotic pathway in B-NHLs. Predictive analyses coupled with database-deposited data suggested that YY1 binds the promoter of the BIRC5/survivin anti-apoptotic gene. Gene Expression Omnibus (GEO) analyses of several B-NHL repositories revealed a conserved positive correlation between YY1 and survivin, both highly expressed, especially in aggressive B-NHLs. Further validation experiments performed in Raji Burkitt’s lymphomas cells, demonstrated that YY1 silencing was associated with survivin downregulation and sensitized the cells to apoptosis. Overall, our results revealed that: (1) YY1 and survivin are positively correlated and overexpressed in B-NHLs, especially in BLs; (2) YY1 strongly binds to the survivin promoter, hence survivin may be suggested as YY1 transcriptional target; (3) YY1 silencing sensitizes Raji cells to drug-induced apoptosis via downregulation of survivin; (4) both YY1 and survivin are potential diagnostic markers and therapeutic targets for the treatment of resistant/relapsed B-NHLs.

Genomic Testing for Relapsed and Refractory Lymphoid Cancers: Understanding Patient Values

BACKGROUND

New clinical genomic assays for lymphoid cancers allow for improved disease stratification and prognostication. At present, clinical implementation has been appropriately limited, owing to a paucity of evidence to support clinical and cost effectiveness. Understanding patients' values for precision oncology under conditions of uncertainty can be used to inform priority-setting decisions.

OBJECTIVES

Our objective was to ascertain patients' qualitative preferences and attitudes for prognostic-based genomic testing.

METHODS

Individuals who were diagnosed with lymphoid cancer between 2000 and 2018 in British Columbia, Canada, were recruited to participate in one of three focus groups. A maximum variation sampling technique was used to capture a diversity of perspectives. A patient partner was involved in the development of the focus group topic guide and presentation materials. All sessions were audio recorded and analyzed using NVivo qualitative analysis software, version 12.

RESULTS

In total, 26 participants took part in focus groups held between November 2018 and February 2019. Results illustrate qualitative preference heterogeneity for situations under which individuals would be willing to undergo genomic testing for relapsed lymphoid cancers. Preferences were highly contextualized within personal experiences with disease and treatment protocols. Hypothetical willingness to pay for testing was contingent on invasiveness, the potential for treatment de-escalation, and personal health benefit.

CONCLUSIONS

Patients are supportive and accepting of evidentiary uncertainty up until the point at which they are required to trade-off the potential for improved quality and length of life. Demand for precision medicine is contingent on expectations for benefit alongside an acknowledgment of the opportunity cost required for implementation. The clinical implementation of precision medicine will be required to address evidentiary uncertainty surrounding personal benefit while ensuring equitable access to emerging innovations.

Clonal relationship in multisited mucosa-associated lymphoid tissue lymphomas: a single-centre experience

Clonal heterogeneity in multisited or recurrent lymphoid neoplasms is a phenomenon that has been increasingly studied in recent years. However, in mucosa-associated lymphoid tissue (MALT) lymphomas it remains largely unexplored. Patients diagnosed at our institution with multisited MALT lymphoma, from January 2009 to October 2018, were studied. Molecular studies were performed for the detection of clonally rearranged immunoglobulin by polymerase chain reaction.In all, 91 patients were included. Of those, 28 had a multisited disease and in 16 clonality studies were done. In eight cases, multifocal involvement was synchronous and in eight metachronous. Patients with non-gastric gastrointestinal tract involvement tended to disseminate within the same tract, without observing other specific dissemination patterns. Four cases (25%) had clonal heterogeneity at the different organs involved. All patients with late relapses (two patients) had different clones. The majority of patients with multisited MALT lymphomas presented with the same clone in the different involved organs, identifying a different clone in those with late relapses. These patients could represent de novo neoplasms, rather than a relapse. This could mean that some individuals might have a genetic predisposition to develop this type of lymphoma and it could also have clinical implications regarding therapeutic decisions.

Mutational landscape of immune surveillance genes in diffuse large B-cell lymphoma

INTRODUCTION

Immune surveillance is the dynamic process whereby the immune system identifies and kills tumor cells based on their aberrant expression of stress-related surface molecules or presentation of tumor neoantigens. It plays a crucial role in controlling the initiation and progression of hematologic cancers such as leukemia and lymphoma, and it has been reported that diffuse large B-cell lymphoma (DLBCL) fails to express specific cell-surface molecules that are necessary for the recognition and elimination of tumor cells.

AREAS COVERED

This review is based on a systematic search strategy to identify relevant literature in the PubMed and Embase databases. Ten candidate genes are identified based on mutational frequency, and functions with detailed mapping performed for hotspot alterations that may have a functional impact on malignant transformation and decreased immune surveillance efficacy.

EXPERT OPINION

Ongoing development of technology and bioinformatics tools combined with data from large clinical cohorts have the potential to define the mutational landscape associated with immune surveillance in DLBCL. Specific functional studies are required to make an unambiguous link between genetic aberrations and biological impact on impaired immune surveillance.

Drug Resistance in Non-Hodgkin Lymphomas

Non-Hodgkin lymphomas (NHL) are lymphoid tumors that arise by a complex process of malignant transformation of mature lymphocytes during various stages of differentiation. The WHO classification of NHL recognizes more than 90 nosological units with peculiar pathophysiology and prognosis. Since the end of the 20^th century, our increasing knowledge of the molecular biology of lymphoma subtypes led to the identification of novel druggable targets and subsequent testing and clinical approval of novel anti-lymphoma agents, which translated into significant improvement of patients’ outcome. Despite immense progress, our effort to control or even eradicate malignant lymphoma clones has been frequently hampered by the development of drug resistance with ensuing unmet medical need to cope with relapsed or treatment-refractory disease. A better understanding of the molecular mechanisms that underlie inherent or acquired drug resistance might lead to the design of more effective front-line treatment algorithms based on reliable predictive markers or personalized salvage therapy, tailored to overcome resistant clones, by targeting weak spots of lymphoma cells resistant to previous line(s) of therapy. This review focuses on the history and recent advances in our understanding of molecular mechanisms of resistance to genotoxic and targeted agents used in clinical practice for the therapy of NHL.

Late relapse in patients with diffuse large B-cell lymphoma: impact of rituximab on their incidence and outcome

Diffuse large B-cell lymphoma (DLBCL) constitutes 25-35% of all non-Hodgkin lymphomas in Western countries. Approximately two thirds of the patients can be cured with standard immuno-chemotherapy. Most relapses occur within 1-2 years from diagnosis, however, the occurrence of relapses after 5 years or more has been described. We aimed at defining the incidence and clinical features of late relapses. Data of 1113 DLBCL patients were analysed. Among the 196 patients relapsing after a first complete remission, 36 (18% of relapses and 3% of all DLBCLs) experienced a recurrence more than 5 years from diagnosis. Late relapsing patients, in comparison with those relapsing earlier, showed a more favourable risk profile at presentation: normal lactate dehydrogenase levels (P = 0·002), early Ann Arbor stage (P = 0·006) and low International Prognostic Index (P = 0·003). The risk of late relapse was lowered by the introduction of rituximab as part of the front-line treatment (P < 0·001). Cause-specific survival (CSS) from the time of relapse was significantly better for late relapsing patients compared to those relapsing early: 5-year CSS rates were 53% and 31%, respectively (P = 0·033). A trend toward a better overall survival was also observed, with 5-year rates after relapse of 47% and 25%, respectively (P = 0·054).

Clinical Relevance of Genomic Changes in Recurrent Pediatric Solid Tumors

PURPOSE: Relapsed/refractory pediatric cancers show poor prognosis; however, their genomic patterns remain unknown. To investigate the genetic mechanisms of tumor relapse and therapy resistance, we characterized genomic alterations in diagnostic and relapsed lesions in patients with relapsed/refractory pediatric solid tumors using targeted deep sequencing. PATIENTS AND METHODS: A targeted sequencing panel covering the exons of 381 cancer genes was used to characterize 19 paired diagnostic and relapsed samples from patients with relapsed/refractory pediatric solid tumors. RESULTS: The mean coverage for all samples was 930.6× (SD = 213.8). Among the 381 genes, 173 single nucleotide variations (SNVs)/insertion-deletions (InDels), 100 copy number alterations, and 1 structural variation were detected. A total of 72.6% of SNVs in primary tumors were also found in recurrent lesions, and 27.2% of SNVs in recurrent tumors had newly occurred. Among SNVs/InDels detected only in recurrent lesions, 71% had a low variant allele fraction (<10%). Patients were classified into three categories based on the mutation patterns after cancer treatment. A significant association between the major mutation patterns and clinical outcome was observed. Patients whose relapsed tumor had fewer mutations than the diagnostic sample tended to be older, had longer progression-free survival, and achieved complete remission after relapse. Contrastingly, patients whose genetic profile only had concordant mutations without any change had the worst outcome. CONCLUSIONS: We characterized genomic changes in recurrent pediatric solid tumors. These findings could help to understand the biology of relapsed childhood cancer and to develop personalized treatment based on their genetic profile.

Mature lymphoid malignancies: origin, stem cells, and chronicity

The chronic behavior of mature lymphoid malignancies, with relapses occurring years apart in many patients, has until recently been unexplained. Patterns of relapse also differ vastly between disease entities, with some being highly curable by chemotherapy whereas others are destined to reemerge after treatment. Lately, the use of next-generation sequencing techniques has revealed essential information on the clonal evolution of lymphoid malignancies. Also, experimental xenograft transplantation point to the possible existence of an ancestral (stem) cell. Such a malignant lymphoid stem cell population could potentially evade current therapies and be the cause of chronicity and death in lymphoma patients; however, the evidence is divergent across disease entities and between studies. In this review we present an overview of genetic studies, case reports, and experimental evidence of the source of mature lymphoid malignancy and discuss the perspectives.