The causal effect of telomere length on the risk of malignant lymphoma: A Mendelian randomization study.

Telomere length (TL) has been implicated in the risk assessment of numerous cancers in observational studies. Nevertheless, the relationship between TL and malignant lymphoma remains unclear, displaying inconsistent patterns across different studies. A summary dataset for genome-wide association study of TL and malignant lymphoma was acquired from the OpenGWAS website. An extensive 2-sample Mendelian randomization (MR) analysis was performed, encompassing various methodologies such as MR-Egger, weighted median, weighted mode, simple mode, and the primary method of inverse-variance weighting (IVW). Sensitivity evaluations were performed using the Cochran Q test, MR-Egger regression, and leave-one-out analysis. The main method IVW revealed that TL substantially increased the risk of Hodgkin lymphoma (HL; odds ratio [OR] = 2.135; 95% confidence interval [CI] = 1.181-3.859; P = .012). Both the IVW and weighted median methods indicated statistical associations between genetically predicted TL and other types of non-HL (OR = 1.671, 95% CI = 1.009-2.768, P = .045; OR = 2.310, 95% CI = 1.033-5.169, P = .042). However, there was no association between TL and diffuse large B-cell lymphoma, follicular lymphoma, or mature T/natural Killer-cell lymphoma, and sensitivity analysis revealed no heterogeneity or horizontal pleiotropy, indicating that the causal effect was robust. Our study shows that TL plays different roles in different types of lymphomas. A longer TL significantly increases the risk of HL and other types of non-HL.

Association of both BCL2 positive and negative follicular lymphoma to clasical Hodgkin lymphoma and/or gray zone lymphoma.

We present a series of 9 follicular lymphomas that progressed/transformed into classical Hodgkin lymphoma (CHL). Three cases of CHL showed a syncytial pattern (SCHL) making the differential diagnosis to Gray zone lymphoma (GZL) challenging. None of these three cases presented in the mediastinum. Based in all molecular data analyzed (BCL2/BCL6 FISH studies, IgH PCR and TNGS with a customized gene panel) we did find clonal relationship between the BCL2-positive FL cases and their CHL components in all cases. The three SCHL/GZL cases showed an activated phenotype according to Hans algorithm, presented the t(14; 18)(q32; q21), two out of three showed B cell markers and all expressed CD30 and p53. Interestingly, we identified three BCL2-negative FL cases with a further diagnosis of CHL expanding the spectrum of these association. In one of these three cases a different mutational profile was found in both the FL and the CHL components. All this data together suggests that CHL associated to BCL2-positive FL could be originated in a common progenitor cell (CPC) that give rise to both FL and CHL, acquiring this last component further genetic events in a linear fashion. On the other hand, no clonal relationship between CHL and BCL2-negative FL could be found, suggesting a fortuity association. Nevertheless, ample series of cases studied with more sensitive techniques are needed to confirm our hypothesis.

Multi-omics profiling of longitudinal samples reveals early genomic changes in follicular lymphoma.

Follicular lymphoma (FL) is the most common indolent type of B-cell non-Hodgkin lymphoma. Advances in treatment have improved overall survival, but early relapse or transformation to aggressive disease is associated with inferior outcome. To identify early genetic events and track tumor clonal evolution, we performed multi-omics analysis of 94 longitudinal biopsies from 44 FL patients; 22 with transformation (tFL) and 22 with relapse without transformation (nFL). Deep whole-exome sequencing confirmed recurrent mutations in genes encoding epigenetic regulators (CREBBP, KMT2D, EZH2, EP300), with similar mutational landscape in nFL and tFL patients. Calculation of genomic distances between longitudinal samples revealed complex evolutionary patterns in both subgroups. CREBBP and KMT2D mutations were identified as genetic events that occur early in the disease course, and cases with CREBBP KAT domain mutations had low risk of transformation. Gains in chromosomes 12 and 18 (TCF4), and loss in 6q were identified as early and stable copy number alterations. Identification of such early and stable genetic events may provide opportunities for early disease detection and disease monitoring. Integrative analysis revealed that tumors with EZH2 mutations exhibited reduced gene expression of numerous histone genes, including histone linker genes. This might contribute to the epigenetic dysregulation in FL.

Identification of genetic subtypes in follicular lymphoma.

Follicular lymphoma (FL) exhibits considerable variability in biological features and clinical trajectories across patients. To dissect the diversity of FL, we utilized a Bernoulli mixture model to identify genetic subtypes in 713 pre-treatment tumor tissue samples. Our analysis revealed the existence of five subtypes with unique genetic profiles that correlated with clinicopathological characteristics. The clusters were enriched in specific mutations as follows: CS (CREBBP and STAT6), TT (TNFAIP3 and TP53), GM (GNA13 and MEF2B), Q (quiescent, for low mutation burden), and AR (mutations of mTOR pathway-related genes). The subtype Q was enriched for patients with stage I disease and associated with a lower proliferative history than the other subtypes. The AR subtype was unique in its enrichment for IgM-expressing FL cases and was associated with advanced-stage and more than 4 nodal sites. The existence of subtypes was validated in an independent cohort of 418 samples from the GALLIUM trial. Notably, patients assigned to the TT subtype consistently experienced inferior progression-free survival when treated with immunochemotherapy. Our findings offer insight into core pathways distinctly linked with each FL cluster and are expected to be informative in the era of targeted therapies.

Transformation of t(14;18)-negative follicular lymphoma to plasmablastic lymphoma: a case report with analysis of genetic evolution.

BACKGROUND: Follicular lymphoma (FL) is characterized by t(14;18)(q32;q21) involving the IGH and BCL2 genes. However, 10-15% of FLs lack the BCL2 rearrangement. These BCL2-rearrangement-negative FLs are clinically, pathologically, and genetically heterogeneous. The biological behavior and histological transformation of such FLs are not adequately characterized. Here, we report the first case of t(14;18)-negative FL that rapidly progressed to plasmablastic lymphoma (PBL). CASE PRESENTATION: A previously healthy 51-year-old man presented with leg swelling. Computed tomography (CT) showed enlarged lymph nodes (LNs) throughout the body, including both inguinal areas. Needle biopsy of an inguinal LN suggested low-grade B-cell non-Hodgkin lymphoma. Excisional biopsy of a neck LN showed proliferation of centrocytic and centroblastic cells with follicular and diffuse growth patterns. Immunohistochemical analysis showed that the cells were positive for CD20, BCL6, CD10, and CD23. BCL2 staining was negative in the follicles and weak to moderately positive in the interfollicular areas. BCL2 fluorescence in situ hybridization result was negative. Targeted next-generation sequencing (NGS) revealed mutations in the TNFRSF14, CREBBP, STAT6, BCL6, CD79B, CD79A, and KLHL6 genes, without evidence of BCL2 or BCL6 rearrangement. The pathologic and genetic features were consistent with t(14;18)-negative FL. Two months after one cycle of bendamustine and rituximab chemotherapy, the patient developed left flank pain. Positron emission tomography/CT showed new development of a large hypermetabolic mass in the retroperitoneum. Needle biopsy of the retroperitoneal mass demonstrated diffuse proliferation of large plasmablastic cells, which were negative for the B-cell markers, BCL2, BCL6, and CD10; they were positive for MUM-1, CD138, CD38, and C-MYC. The pathologic findings were consistent with PBL. The clonal relationship between the initial FL and subsequent PBL was analyzed via targeted NGS. The tumors shared the same CREBBP, STAT6, BCL6, and CD79B mutations, strongly suggesting that the PBL had transformed from a FL clone. The PBL also harbored BRAF V600E mutation and IGH::MYC fusion in addition to IGH::IRF4 fusion. CONCLUSIONS: We propose that transformation or divergent clonal evolution of FL into PBL can occur when relevant genetic mutations are present. This study broadens the spectrum of histological transformation of t(14;18)-negative FL and emphasizes its biological and clinical heterogeneity.

Predicting regulatory mutations and their target genes by new computational integrative analysis: A study of follicular lymphoma.

Mutations in DNA regulatory regions are increasingly being recognized as important drivers of cancer and other complex diseases. These mutations can regulate gene expression by affecting DNA-protein binding and epigenetic profiles, such as DNA methylation in genome regulatory elements. However, identifying mutation hotspots associated with expression regulation and disease progression in non-coding DNA remains a challenge. Unlike most existing approaches that assign a mutation score to individual single nucleotide polymorphisms (SNP), a mutation block (MB)-based approach was introduced in this study to assess the collective impact of a cluster of SNPs on transcription factor-DNA binding affinity, differential gene expression (DEG), and nearby DNA methylation. Moreover, the long-distance target genes of functional MBs were identified using a new permutation-based algorithm that assessed the significance of correlations between DNA methylation at regulatory regions and target gene expression. Two new Python packages were developed. The Differential Methylation Region (DMR-analysis) analysis tool was used to detect DMR and map them to regulatory elements. The second tool, an integrated DMR, DEG, and SNP analysis tool (DDS-analysis), was used to combine the omics data to identify functional MBs and long-distance target genes. Both tools were validated in follicular lymphoma (FL) cohorts, where not only known functional MBs and their target genes (BCL2 and BCL6) were recovered, but also novel genes were found, including CDCA4 and JAG2, which may be associated with FL development. These genes are linked to target gene expression and are significantly correlated with the methylation of nearby DNA sequences in FL. The proposed computational integrative analysis of multiomics data holds promise for identifying regulatory mutations in cancer and other complex diseases.

Integrated single cell analysis reveals co-evolution of malignant B cells and tumor micro-environment in transformed follicular lymphoma.

Histological transformation of follicular lymphoma (FL) to aggressive forms is associated with poor outcome. Phenotypic consequences of this evolution and its impact on the tumor microenvironment (TME) remain unknown. We perform single-cell whole genome sequencing (scWGS) and transcriptome sequencing (scWTS) of 11 paired pre/post-transformation patient samples and scWTS of additional samples from patients without transformation. Our analysis reveals evolutionary dynamics of transformation at single-cell resolution, highlighting a shifting TME landscape, with an emerging immune-cell exhaustion signature, co-evolving with the shifting malignant B phenotype in a regulatory ecosystem. Integration of scWGS and scWTS identifies malignant cell pathways upregulated during clonal tumor evolution. Using multi-color immunofluorescence, we transfer these findings to a TME-based transformation biomarker, subsequently validated in two independent pretreatment cohorts. Taken together, our results provide a comprehensive view of the combined genomic and phenotypic evolution of malignant cells during transformation and shifting crosstalk between malignant cells and the TME.

Frequent CDKN2B/P15 and DAPK1 methylation in duodenal follicular lymphoma is related to duodenal reactive lymphoid hyperplasia.

Duodenal type follicular lymphoma (DFL), a rare entity of follicular lymphoma (FL), is clinically indolent and is characterized by a low histological grade compared with nodal follicular lymphoma (NFL). Our previous reports revealed that DFL shares characteristics of both NFL and mucosa-associated lymphoid tissue (MALT) lymphoma in terms of clinical and biological aspects, suggesting its pathogenesis may involve antigenic stimulation. In contrast to NFL, the genomic methylation status of DFL is still challenging. Here, we determined the methylation profiles of DNAs from patients with DFL (n = 12), NFL (n = 10), duodenal reactive lymphoid hyperplasia (D-RLH) (n = 7), nodal reactive lymphoid hyperplasia (N-RLH) (n = 5), and duodenal samples from normal subjects (NDU) (n = 5) using methylation specific PCR of targets previously identified in MALT lymphoma (CDKN2B/P15, CDKN2A/P16, CDKN2C/P18, MGMT, hMLH-1, TP73, DAPK, HCAD). DAPK1 was frequently methylated in DFL (9/12; 75%), NFL (9/10; 90%), and D-RLH (5/7; 71%). CDKN2B/P15 sequences were methylated in six DFL samples and in only one NFL sample. Immunohistochemical analysis showed that p15 expression inversely correlated with methylation status. Genes encoding other cyclin-dependent kinase inhibitors (CDKN2A/P16, CDKN2C/P18) were not methylated in DFL samples. Methylation of the genes of interest was not detected in DNAs from D-RLH, except for DAPK1, and the difference in the extent of methylation between NDU and D-RLH was statistically significant (P = 0.013). Our results suggest that D-RLH serves as a reservoir for the development of DFL and that methylation of CDKN2B/P15 plays an important role in this process.

Clonal evolution and relapse in early-stage follicular lymphoma - a tree with many branches†.

Follicular lymphoma (FL) is an indolent B-cell neoplasm characterised by multistep evolution from premalignant precursor cells carrying the hallmark t(14;18) translocation in the majority of cases. In a new article in The Journal of Pathology, samples of relapsed early-stage FL - primary manifestation and relapse with or without transformation - initially treated with radiotherapy only, were studied for clonal relationships and evolution. Using somatic mutations and the rearranged immunoglobulin sequences as markers, the majority of paired lymphoma samples showed so-called branched evolution from a common, possibly premalignant progenitor cell, with both shared and private mutations. In addition, clonally unrelated cases were identified. This and previous studies with similar findings clearly document that relapse or transformation of FL in many instances not necessarily represents a linear progression of disease due to acquisition of additional mutations and therapy resistance, but rather new outgrowths derived from a pool of clonally related, long-lived, and low proliferating precursor cells, or even unrelated second neoplasms. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Translational insights into the genetics and immunobiology of relapsed/refractory follicular lymphoma.

Although follicular lymphoma (FL) is traditionally classified as an indolent subtype of B cell non-Hodgkin lymphoma, clinical trajectories are often diverse based on unique disease biology, and many patients will eventually experience relapse of their disease. Furthermore, progression of disease within 24 months is associated with increased mortality rates for FL. In the last five years, we have witnessed an upsurge in the commercial availability of targeted therapies for relapsed/refractory (R/R) FL, including chimeric antigen receptor-T (CAR-T) products, bispecific T cell engagers (BiTEs), epigenetic modifier therapies, and next-generation Bruton tyrosine kinase (BTK) inhibitors. Furthermore, clinical trial options have increased tremendously and now include combinatorial strategies that exert synergy against malignant germinal center B cells. Here, we provide a 2024 update of novel therapeutic agents whose development has been informed by recent advances in the genetics and immunobiology of R/R FL. Specifically, we emphasize high-value targeted therapeutics, including anti-CD3 x anti-CD20 BiTEs and adoptive T cell therapies. We discuss prospects on selection and sequencing of BiTEs and CAR-T therapies for patients with R/R FL. We underscore the principles of FL pathobiology that are paving way for future drug discovery and shed insight into therapeutic targeting within nodal basins based on our increasing understanding of the FL microenvironment. Finally, we summarize how a greater knowledge of FL immunobiology can inform risk stratification and therapy selection on a personalized basis for R/R FL in 2025.

Generation and External Validation of a Histologic Transformation Risk Model for Patients with Follicular Lymphoma.

Follicular lymphoma (FL) is the most frequent indolent lymphoma. Some patients (10%-15%) experience histologic transformation (HT) to a more aggressive lymphoma, usually diffuse large B-cell lymphoma (DLBCL). This study aimed to validate and improve a genetic risk model to predict HT at diagnosis.We collected mutational data from diagnosis biopsies of 64 FL patients. We combined them with the data from a previously published cohort (total n = 104; 62 from nontransformed and 42 from patients who did transform to DLBCL). This combined cohort was used to develop a nomogram to estimate the risk of HT. Prognostic mutated genes and clinical variables were assessed using Cox regression analysis to generate a risk model. The model was internally validated by bootstrapping and externally validated in an independent cohort. Its performance was evaluated using a concordance index and a calibration curve. The clinicogenetic nomogram included the mutational status of 3 genes (HIST1HE1, KMT2D, and TNFSR14) and high-risk Follicular Lymphoma International Prognostic Index and predicted HT with a concordance index of 0.746. Patients were classified as being at low or high risk of transformation. The probability HT function at 24 months was 0.90 in the low-risk group vs 0.51 in the high-risk group and, at 60 months, 0.71 vs 0.15, respectively. In the external validation cohort, the probability HT function in the low-risk group was 0.86 vs 0.54 in the high-risk group at 24 months, and 0.71 vs 0.32 at 60 months. The concordance index in the external cohort was 0.552. In conclusion, we propose a clinicogenetic risk model to predict FL HT to DLBLC, combining genetic alterations in HIST1H1E, KMT2D, and TNFRSF14 genes and clinical features (Follicular Lymphoma International Prognostic Index) at diagnosis. This model could improve the management of FL patients and allow treatment strategies that would prevent or delay transformation.

Clonal Hematopoiesis and Bone Marrow Infiltration in Patients With Follicular Helper T-Cell Lymphoma of Angioimmunoblastic Type.

Follicular helper T-cell (TFH) lymphoma harbors recurrent mutations of RHOAG17V, IDH2R172, TET2, and DNMT3A. TET2 and DNMT3A mutations are the most frequently affected genes in clonal hematopoiesis (CH). The aim of our study was to investigate the frequency of CH in bone marrow biopsies (BMB) of TFH/angioimmunoblastic T-cell lymphoma (TFH-AITL) patients and its association with myeloid neoplasms. A total of 29 BMB from 22 patients with a diagnosis of TFH-AITL were analyzed by next-generation sequencing (NGS) with a custom panel. Morphologically, 5 BMB revealed that TFH-AITL infiltrates of >5% of bone marrow (BM) cellularity confirmed in 4 cases by NGS-based T-cell clonality. IDH2R172 was demonstrated only in 1 (3%) of 29, and RHOAG17V in 2 (7%) of 29 samples. TET2 and DNMT3A were identified in 24 (83%) of 29 and 17 (59%) of 29 BMB, respectively. In the parallel lymph node the frequencies of mutations were 27% (IDH2R172), 64% (RHOAG17V), 86% (TET2), and 50% (DNMT3A). TET2 and/or DNMT3A mutations identical in lymph node and BMB were present in 18 (82%) of 22 patients, regardless of BM infiltration. In 3 cases the CH mutations were detected 13, 41, and 145 months before TFH-AITL diagnosis. Cases with TET2/DNMT3A mutations and BM variant allele frequencies >40% (7/18, 39%) showed lower blood counts. However, only low platelet count was statistically significant (P = .024). Myeloid neoplasms and/or myelodysplastic syndrome-related mutations were identified in 4 cases (4/22; 18%); all with high TET2 variant allele frequencies (>40%; P = .0114). In conclusion, CH is present in 82% of TFH-AITL and can be demonstrated up to 145 months before TFH-AITL diagnosis. NGS T-cell clonality analysis is an excellent tool to confirm TFH-AITL BM infiltration. Concurrent myeloid neoplasms were identified in 18% of the cases and were associated with TET2 mutations with high allelic burden (>40%). We demonstrated that myeloid neoplasms might occur simultaneously or precede the diagnosis of TFH lymphoma.

Long-Term Follow-Up of Patients With Follicular Lymphoma Using Next Generation Sequencing to Detect Minimal Residual Disease.

BACKGROUND: Follicular lymphoma (FL) is a highly treatable, indolent non-Hodgkin lymphoma. Although FL is considered incurable, a patient without progression of disease by 24 months after treatment is predicted to have a survival consistent with persons without lymphoma. Using a sensitive assessment of minimal residual disease (MRD), we tested the hypothesis that MRD monitoring can predict long term remissions. METHODS: Unselected patients who were in a clinical remission for at least 24 months after their last treatment were enrolled and monitored prospectively for MRD detectability using a sensitive next-generation sequencing assay (clonoSEQ, Adaptive Biotechnologies, Seattle, WA). RESULTS: Forty-seven consecutive patients were monitored. We evaluated the MRD thresholds 10-4, 10-5, and 10-6 for the ability to predict long-term remissions in this cohort and determined that undetectable disease at 10-6 was the best predictor with a specificity and negative predictive value (NPV) of 70% and 100%, respectively. While 3 patients exhibited clinical disease progression during the course of the study, none of the 31 patients with persistent MRD undetectability at 10-6 experienced relapse. CONCLUSIONS: A significant proportion (31/47; 66.0%) of FL patients in clinical remission after ≥24 months following last therapy were undetectable at 10-6 by a sensitive assay of MRD. The threshold of sensitivity was 100%, specificity 70%, with a PPV of 19%, but a NPV of 100%. Although longer follow-up is needed for confirmation, many of these patients may continue to have durable complete remissions.

Follicular lymphoma regulatory T-cell origin and function.

Introduction: Follicular Lymphoma (FL) results from the malignant transformation of germinal center (GC) B cells. FL B cells display recurrent and diverse genetic alterations, some of them favoring their direct interaction with their cell microenvironment, including follicular helper T cells (Tfh). Although FL-Tfh key role is well-documented, the impact of their regulatory counterpart, the follicular regulatory T cell (Tfr) compartment, is still sparse. Methods: The aim of this study was to characterize FL-Tfr phenotype by cytometry, gene expression profile, FL-Tfr origin by transcriptomic analysis, and functionality by in vitro assays. Results: CD4+CXCR5+CD25hiICOS+ FL-Tfr displayed a regulatory program that is close to classical regulatory T cell (Treg) program, at the transcriptomic and methylome levels. Accordingly, Tfr imprinting stigmata were found on FL-Tfh and FL-B cells, compared to their physiological counterparts. In addition, FL-Tfr co-culture with autologous FL-Tfh or cytotoxic FL-CD8+ T cells inhibited their proliferation in vitro. Finally, although FL-Tfr shared many characteristics with Treg, TCR sequencing analyses demonstrated that part of them derived from precursors shared with FL-Tfh. Discussion: Altogether, these findings uncover the role and origin of a Tfr subset in FL niche and may be useful for lymphomagenesis knowledge and therapeutic management.

Neoantigen landscape supports feasibility of personalized cancer vaccine for follicular lymphoma.

ABSTRACT: Personalized cancer vaccines designed to target neoantigens represent a promising new treatment paradigm in oncology. In contrast to classical idiotype vaccines, we hypothesized that "polyvalent" vaccines could be engineered for the personalized treatment of follicular lymphoma (FL) using neoantigen discovery by combined whole-exome sequencing (WES) and RNA sequencing (RNA-seq). Fifty-eight tumor samples from 57 patients with FL underwent WES and RNA-seq. Somatic and B-cell clonotype neoantigens were predicted and filtered to identify high-quality neoantigens. B-cell clonality was determined by the alignment of B-cell receptor (BCR) CDR3 regions from RNA-seq data, grouping at the protein level, and comparison with the BCR repertoire from healthy individuals using RNA-seq data. An average of 52 somatic mutations per patient (range, 2-172) were identified, and ≥2 (median, 15) high-quality neoantigens were predicted for 56 of 58 FL samples. The predicted neoantigen peptides were composed of missense mutations (77%), indels (9%), gene fusions (3%), and BCR sequences (11%). Building off of these preclinical analyses, we initiated a pilot clinical trial using personalized neoantigen vaccination combined with PD-1 blockade in patients with relapsed or refractory FL (#NCT03121677). Synthetic long peptide vaccines targeting predicted high-quality neoantigens were successfully synthesized for and administered to all 4 patients enrolled. Initial results demonstrate feasibility, safety, and potential immunologic and clinical responses. Our study suggests that a genomics-driven personalized cancer vaccine strategy is feasible for patients with FL, and this may overcome prior challenges in the field. This trial was registered at www.ClinicalTrials.gov as #NCT03121677.

Thyroid papillary carcinoma combined with primary follicular lymphoma: a case report.

BACKGROUND: Papillary thyroid carcinoma (PTC) stands out as the most prevalent epithelial malignant thyroid tumor. Thyroid primary follicular lymphoma (PFL) represents a rare malignant tumor originating from mesenchymal tissues. The concurrent occurrence of PTC and PFL is exceptionally rare, particularly in the context of Hashimoto's thyroiditis, presenting significant challenges in clinical diagnosis and treatment. CASE DEMONSTRATION: A 44-year-old female patient presented with a neck mass persisting for over 1 month. The patient underwent surgery, and the incised tissues were subjected to pathology examinations, along with immunohistochemistry and next-generation sequencing tests suggestive of an EZH2 gene mutation in the tumor cells. The final pathological diagnosis confirmed the presence of PTC combined with PFL. Following a 27-month follow-up, the patient displayed no signs of recurrence or metastasis. CONCLUSIONS: The concurrent occurrence of PTC and PFL poses notable challenges in clinical practice, requiring careful consideration in diagnosis and treatment. Herein, we present a rare case of PTC combined with PFL featuring an EZH2 gene mutation, which can be easily overlooked in the context of Hashimoto's thyroiditis. The patient's favorable response to surgical and radiotherapeutic interventions underscores the importance of accurate diagnosis and tailored treatment strategies in similar cases.

Patients with Classic Hodgkin Lymphoma and Follicular Lymphoma Compared to Single Malignancy Controls.

Classic Hodgkin lymphoma (CHL) can arise in patients with low-grade B-cell lymphoma. The features of CHL arising in follicular lymphoma (FL) and its outcome are still unclear, mainly due to the very few cases reported. This study compares 17 patients with CHL and FL to 2 control groups: 1 of 26 patients with FL and a second of 60 patients older than 40 when diagnosed with CHL. Of the FL and CHL patients, 8 had simultaneous FL and CHL, while 9 had FL first, followed by CHL 4.7 years later on average. The age at the diagnosis of FL was 61 years for patients with synchronous FL and CHL and of 60 years for FL, followed by CHL at 65 years. Patients with FL only were, on average, 59 years old at presentation, while CHL patients were 61. FL was grade 1-2 in 75% of FL and CHL patients and 67% of FL first and CHL second patients, lower proportions than in the FL control group-92%. Epstein-Barr virus (EBV) was detected in a lower fraction (29%) of the FL and CHL group than in CHL-only controls (46%). BCL2 translocations were detected in 4 of the 7 cases with FL, but in positive cases, the rearrangement was also present in the CHL component, indicating a clonal relationship between FL and CHL. Patients with FL and CHL treated for CHL had an initial outcome more similar to FL than to CHL controls.

Two recurrent types of IGH::5' BCL2 breakpoints representing cytogenetic ins(14;18)(q32;q21q21) and t(14;18)(q32;q21), mediated by the VDJ and class switch recombination processes, respectively.

We describe two types of IGH::BCL2 breakpoints involving the 5' region of BCL2 (5' BCL2). One was ins(14;18)(q32;q21q21) observed in 2 follicular lymphoma (FL) cases, in which IGH was cleaved at 3' of IGHD and 5' of IGHJ and BCL2 was cleaved at 5' BCL2 and downstream regions, and a 281- or 201-kilobase pair fragment containing the BCL2 protein-coding sequences was invertedly inserted into IGH. In another type observed in 2 FL and 2 chronic lymphocytic leukemia (CLL) cases, breakage and reunion occurred within the switch region associated with IGHM (Sµ) and 5' BCL2, creating IGH Sµ::5' BCL2 fusion sequences on der(18)t(14;18)(q32;q21). The former is considered to be mediated by VDJ-recombination, while the latter by the class switch recombination process. There were no particular features in FL or CLL cases with IGH::5' BCL2 breakpoints compared with those with t(14;18)(q32;q21)/IGH::BCL2 involving the 3' breakpoint cluster regions.