A metabolic dependency of EBV can be targeted to hinder B cell transformation

After infection of B cells, Epstein-Barr virus (EBV) engages host pathways that mediate cell proliferation and transformation, contributing to the propensity of the virus to drive immune dysregulation and lymphomagenesis. We found that the EBV protein EBNA2 initiates nicotinamide adenine dinucleotide (NAD) de novo biosynthesis by driving expression of the metabolic enzyme indoleamine 2,3-dioxygenase 1 (IDO1) in infected B cells. Virus-enforced NAD production sustained mitochondrial complex I activity, to match adenosine triphosphate (ATP) production with bioenergetic requirements of proliferation and transformation. In transplant patients, IDO1 expression in EBV-infected B cells, and a serum signature of increased IDO1 activity, preceded development of lymphoma. In humanized mice infected with EBV, IDO1 inhibition reduced both viremia and lymphomagenesis. Virus-orchestrated NAD biosynthesis is therefore a druggable metabolic vulnerability of EBV-driven B cell transformation, opening therapeutic possibilities for EBV-related diseases.

Detection of disease-specific signatures in B cell repertoires of lymphomas using machine learning

The classification of B cell lymphomas-mainly based on light microscopy evaluation by a pathologist-requires many years of training. Since the B cell receptor (BCR) of the lymphoma clonotype and the microenvironmental immune architecture are important features discriminating different lymphoma subsets, we asked whether BCR repertoire next-generation sequencing (NGS) of lymphoma-infiltrated tissues in conjunction with machine learning algorithms could have diagnostic utility in the subclassification of these cancers. We trained a random forest and a linear classifier via logistic regression based on patterns of clonal distribution, VDJ gene usage and physico-chemical properties of the top-n most frequently represented clonotypes in the BCR repertoires of 620 paradigmatic lymphoma samples-nodular lymphocyte predominant B cell lymphoma (NLPBL), diffuse large B cell lymphoma (DLBCL) and chronic lymphocytic leukemia (CLL)-alongside with 291 control samples. With regard to DLBCL and CLL, the models demonstrated optimal performance when utilizing only the most prevalent clonotype for classification, while in NLPBL-that has a dominant background of non-malignant bystander cells-a broader array of clonotypes enhanced model accuracy. Surprisingly, the straightforward logistic regression model performed best in this seemingly complex classification problem, suggesting linear separability in our chosen dimensions. It achieved a weighted F1-score of 0.84 on a test cohort including 125 samples from all three lymphoma entities and 58 samples from healthy individuals. Together, we provide proof-of-concept that at least the 3 studied lymphoma entities can be differentiated from each other using BCR repertoire NGS on lymphoma-infiltrated tissues by a trained machine learning model.

Loss of Dnmt3a increases self-renewal and resistance to pegIFN-α in JAK2-V617F-positive myeloproliferative neoplasms

ABSTRACT

Pegylated interferon alfa (pegIFN-α) can induce molecular remissions in patients with JAK2-V617F-positive myeloproliferative neoplasms (MPNs) by targeting long-term hematopoietic stem cells (LT-HSCs). Additional somatic mutations in genes regulating LT-HSC self-renewal, such as DNMT3A, have been reported to have poorer responses to pegIFN-α. We investigated whether DNMT3A loss leads to alterations in JAK2-V617F LT-HSC functions conferring resistance to pegIFN-α treatment in a mouse model of MPN and in hematopoietic progenitors from patients with MPN. Long-term treatment with pegIFN-α normalized blood parameters and reduced splenomegaly and JAK2-V617F chimerism in single-mutant JAK2-V617F (VF) mice. However, pegIFN-α in VF;Dnmt3aΔ/Δ (VF;DmΔ/Δ) mice worsened splenomegaly and failed to reduce JAK2-V617F chimerism. Furthermore, LT-HSCs from VF;DmΔ/Δ mice compared with VF were less prone to accumulate DNA damage and exit dormancy upon pegIFN-α treatment. RNA sequencing showed that IFN-α induced stronger upregulation of inflammatory pathways in LT-HSCs from VF;DmΔ/Δ than from VF mice, indicating that the resistance of VF;DmΔ/Δ LT-HSC was not due to failure in IFN-α signaling. Transplantations of bone marrow from pegIFN-α-treated VF;DmΔ/Δ mice gave rise to more aggressive disease in secondary and tertiary recipients. Liquid cultures of hematopoietic progenitors from patients with MPN with JAK2-V617F and DNMT3A mutation showed increased percentages of JAK2-V617F-positive colonies upon IFN-α exposure, whereas in patients with JAK2-V617F alone, the percentages of JAK2-V617F-positive colonies decreased or remained unchanged. PegIFN-α combined with 5-azacytidine only partially overcame resistance in VF;DmΔ/Δ mice. However, this combination strongly decreased the JAK2-mutant allele burden in mice carrying VF mutation only, showing potential to inflict substantial damage preferentially to the JAK2-mutant clone.

The Genetic Landscape of Primary Breast Marginal Zone Lymphoma Identifies a Mutational-driven Disease With Similarities to Ocular Adnexal Lymphoma

Extranodal marginal zone lymphomas (eMZL) can occur in any organ and site of the body. Recent research has shown that they differ from organ to organ in terms of their mutational profile. In this study, we investigated a cohort of primary breast marginal zone lymphomas (PBMZL) to get a better insight into their morphologic and molecular profile. A cohort of 15 cases (14 female and 1 male) was characterized by immunohistochemistry (IHC) for 19 markers, fluorescence in situ hybridization (FISH), and high throughput sequencing (HTS) using a lymphoma panel comprising 172 genes. In addition, PCR for the specific detection of Borrelia spp. and metagenomics whole genome sequencing were performed for infectious agent profiling. Follicular colonization was observed in most cases, while lymphoepithelial lesions, though seen in many cases, were not striking. All 15 cases were negative for CD5, CD11c, and CD21 and positive for BCL2 and pan B-cell markers. There were no cases with BCL2, BCL10, IRF4, MALT1, or MYC translocation; only 1 had a BCL6 rearrangement. HTS highlighted TNFAIP3 (n=4), KMT2D (n=2), and SPEN (n=2) as the most frequently mutated genes. There were no Borrelia spp., and no other pathogens detected in our cohort. One patient had a clinical history of erythema chronicum migrans affecting the same breast. PBMZL is a mutation-driven disease rather than fusion-driven. It exhibits mutations in genes encoding components affecting the NF-κB pathway, chromatin modifier-encoding genes, and NOTCH pathway-related genes. Its mutational profile shares similarities with ocular adnexal and nodal MZL.

The glutaminase inhibitor CB-839 targets metabolic dependencies of JAK2-mutant hematopoiesis in MPN

ABSTRACT

Hyperproliferation of myeloid and erythroid cells in myeloproliferative neoplasms (MPN) driven by the JAK2-V617F mutation is associated with altered metabolism. Given the central role of glutamine in anabolic and catabolic pathways, we examined the effects of pharmacologically inhibiting glutaminolysis, that is, the conversion of glutamine (Gln) to glutamate (Glu), using CB-839, a small molecular inhibitor of the enzyme glutaminase (GLS). We show that CB-839 strongly reduced the mitochondrial respiration rate of bone marrow cells from JAK2-V617F mutant (VF) mice, demonstrating a marked dependence of these cells on Gln-derived ATP production. Consistently, in vivo treatment with CB-839 normalized blood glucose levels, reduced splenomegaly and decreased erythrocytosis in VF mice. These effects were more pronounced when CB-839 was combined with the JAK1/2 inhibitor ruxolitinib or the glycolysis inhibitor 3PO, indicating possible synergies when cotargeting different metabolic and oncogenic pathways. Furthermore, we show that the inhibition of glutaminolysis with CB-839 preferentially lowered the proportion of JAK2-mutant hematopoietic stem cells (HSCs). The total number of HSCs was decreased by CB-839, primarily by reducing HSCs in the G1 phase of the cell cycle. CB-839 in combination with ruxolitinib also strongly reduced myelofibrosis at later stages of MPN. In line with the effects shown in mice, proliferation of CD34+ hematopoietic stem and progenitor cells from polycythemia vera patients was inhibited by CB-839 at nanomolar concentrations. These data suggest that inhibiting GLS alone or in combination with inhibitors of glycolysis or JAK2 inhibitors represents an attractive new therapeutic approach to MPN.

Case report: 'Atypical Richter transformation from CLL-type monoclonal B-cell lymphocytosis into Burkitt lymphoma in a treatment naïve patient'

Background

Richter transformation refers to the progression of an initially slow-growing small lymphocytic lymphoma/chronic lymphocytic leukemia (SLL/CLL) into an aggressive lymphoma, typically diffuse large B-cell lymphoma (DLBCL) or Hodgkin lymphoma.

Case presentation

The patient presented with a rapid onset of localized cervical swelling, accompanied by monoclonal B-cell lymphocytosis displaying a CLL immunophenotype. The histopathological analysis identified a Burkitt lymphoma (BL) located in the submandibular gland and adjacent lymph node. The patient's bone marrow displayed a minor infiltration of monoclonal B-cells with a CLL immunophenotype (< 10%). Molecular analysis demonstrated the presence of the same monoclonal rearrangement in the framework region (FR3 region) of the immunoglobulin heavy chain (IGH) locus. High-throughput sequencing of the immunoglobulin heavy and light chains also confirmed the presence of the same rearrangement in SLL/CLL and in the Burkitt lymphoma sample, but also highlighted the presence of a second rearrangement in the Burkitt lymphoma cells, not shared with the SLL/CLL cells in the bone marrow. The patient was treated with DA-EPOCH-R, which lead to a complete metabolic response.

Conclusion

This report provides an exceptionally rare description of a CLL-type monoclonal B-cell lymphocytosis transforming into a very aggressive Burkitt lymphoma in a treatment naïve patient.

IL-1β promotes MPN disease initiation by favoring early clonal expansion of JAK2-mutant hematopoietic stem cells

ABSTRACT

JAK 2-V617F is the most frequent somatic mutation causing myeloproliferative neoplasm (MPN). JAK2-V617F can be found in healthy individuals with clonal hematopoiesis of indeterminate potential (CHIP) with a frequency much higher than the prevalence of MPNs. The factors controlling the conversion of JAK2-V617F CHIP to MPN are largely unknown. We hypothesized that interleukin-1β (IL-1β)-mediated inflammation can favor this progression. We established an experimental system using bone marrow (BM) transplantations from JAK2-V617F and GFP transgenic (VF;GFP) mice that were further crossed with IL-1β-/- or IL-1R1-/- mice. To study the role of IL-1β and its receptor on monoclonal evolution of MPN, we performed competitive BM transplantations at high dilutions with only 1 to 3 hematopoietic stem cells (HSCs) per recipient. Loss of IL-1β in JAK2-mutant HSCs reduced engraftment, restricted clonal expansion, lowered the total numbers of functional HSCs, and decreased the rate of conversion to MPN. Loss of IL-1R1 in the recipients also lowered the conversion to MPN but did not reduce the frequency of engraftment of JAK2-mutant HSCs. Wild-type (WT) recipients transplanted with VF;GFP BM that developed MPNs had elevated IL-1β levels and reduced frequencies of mesenchymal stromal cells (MSCs). Interestingly, frequencies of MSCs were also reduced in recipients that did not develop MPNs, had only marginally elevated IL-1β levels, and displayed low GFP-chimerism resembling CHIP. Anti-IL-1β antibody preserved high frequencies of MSCs in VF;GFP recipients and reduced the rate of engraftment and the conversion to MPN. Our results identify IL-1β as a potential therapeutic target for preventing the transition from JAK2-V617F CHIP to MPNs.

Development of Resistance to Type II JAK2 Inhibitors in MPN Depends on AXL Kinase and Is Targetable

PURPOSE

Myeloproliferative neoplasms (MPN) dysregulate JAK2 signaling. Because clinical JAK2 inhibitors have limited disease-modifying effects, type II JAK2 inhibitors such as CHZ868 stabilizing inactive JAK2 and reducing MPN clones, gain interest. We studied whether MPN cells escape from type ll inhibition.

EXPERIMENTAL DESIGN

MPN cells were continuously exposed to CHZ868. We used phosphoproteomic analyses and ATAC/RNA sequencing to characterize acquired resistance to type II JAK2 inhibition, and targeted candidate mediators in MPN cells and mice.

RESULTS

MPN cells showed increased IC50 and reduced apoptosis upon CHZ868 reflecting acquired resistance to JAK2 inhibition. Among >2,500 differential phospho-sites, MAPK pathway activation was most prominent, while JAK2-STAT3/5 remained suppressed. Altered histone occupancy promoting AP-1/GATA binding motif exposure associated with upregulated AXL kinase and enriched RAS target gene profiles. AXL knockdown resensitized MPN cells and combined JAK2/AXL inhibition using bemcentinib or gilteritinib reduced IC50 to levels of sensitive cells. While resistant cells induced tumor growth in NOD/SCID gamma mice despite JAK2 inhibition, JAK2/AXL inhibition largely prevented tumor progression. Because inhibitors of MAPK pathway kinases such as MEK are clinically used in other malignancies, we evaluated JAK2/MAPK inhibition with trametinib to interfere with AXL/MAPK-induced resistance. Tumor growth was halted similarly to JAK2/AXL inhibition and in a systemic cell line-derived mouse model, marrow infiltration was decreased supporting dependency on AXL/MAPK.

CONCLUSIONS

We report on a novel mechanism of AXL/MAPK-driven escape from type II JAK2 inhibition, which is targetable at different nodes. This highlights AXL as mediator of acquired resistance warranting inhibition to enhance sustainability of JAK2 inhibition in MPN.

Primary bone diffuse large B-cell lymphoma (PB-DLBCL): a distinct extranodal lymphoma of germinal centre origin, with a common EZB-like mutational profile and good prognosis

AIMS

Primary bone diffuse large B-cell lymphoma (PB-DLBCL) is not recognized as a separate entity by the current classification systems. Here we define and highlight its distinctive clinical presentation, morphology, phenotype, gene expression profile (GEP), and molecular genetics.

METHODS

We collected 27 respective cases and investigated their phenotype, performed gDNA panel sequencing covering 172 genes, and carried out fluorescence in situ hybridization to evaluate MYC, BCL2, and BCL6 translocations. We attempted to genetically subclassify cases using the Two-step classifier and performed GEP for cell-of-origin subtyping and in silico comparison to uncover up- and downregulated genes as opposed to other DLBCL.

RESULTS

Most cases (n = 22) were germinal centre B-cell-like (GCB) by immunohistochemistry and all by GEP. Additionally, PB-DLBCL had a mutational profile similar to follicular lymphoma and nodal GCB-DLBCL, with the exception of more frequent TP53 and B2M mutations. The GEP of PB-DLBCL was unique, and the frequency of BCL2 rearrangements was lower compared to nodal GCB-DLBCL. The Two-step classifier categorized eight of the cases as EZB, three as ST2, and one as MCD.

CONCLUSION

This study comprehensively characterizes PB-DLBCL as a separate entity with distinct clinical and morpho-molecular features. These insights may aid in developing tailored therapeutic strategies and shed light on its pathogenesis.

Molecular characterization and genetic subclassification comparison of diffuse large B-cell lymphoma (DLBCL) - real-life experience with 74 cases

INTRODUCTION

Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous entity. Lately, several algorithms achieving therapeutically and prognostically relevant DLBCL subclassification have been published.

METHODS

A cohort of 74 routine DLBCL cases was broadly characterized by immunohistochemistry (IHC), fluorescence in situ hybridization (FISH) of the BCL2, BCL6 and MYC loci, and comprehensive high throughput sequencing (HTS). Based on the genetic alterations found, cases were reclassified using two probabilistic tools - LymphGen and Two-step classifier, allowing for comparison of the two models.

RESULTS

Hans and Tally's overall IHC-based subclassification success rate was 96% and 82%, respectively. HTS and FISH data allowed the LymphGen algorithm to successfully classify 11/55 cases, (1 - BN2, 7 - EZB, 1 - MCD, and 2 - genetically composite EZB/N1). The total subclassification rate was 20%. On the other hand, the Two-step classifier categorized 36/55 cases, with 65.5% success (9 - BN2, 12 - EZB, 9 - MCD, 2 - N1, and 4 - ST2). Clinical correlations highlighted MCD as an aggressive subtype associated with higher relapse and mortality.

CONCLUSIONS

The Two-step algorithm has a better success rate at subclassifying DLBCL cases based on genetic differences. Further improvement of the classifiers is required to increase the number of classifiable cases and thus prove their applicability in routine diagnostics.

R-CODOX-M/R-IVAC versus DA-EPOCH-R in patients with newly diagnosed Burkitt lymphoma (HOVON/SAKK): final results of a multicentre, phase 3, open-label, randomised trial

BACKGROUND

Patients with newly diagnosed high-risk Burkitt lymphoma are treated with high-intensity immune-chemotherapy regimens such as R-CODOX-M/R-IVAC or with lower-intensity regimens such as DA-EPOCH-R. The aim of this study was to make a formal comparison between these regimens.

METHODS

This multicentre, phase 3, open-label, randomised study was done in 26 clinical centres in the Netherlands, Belgium, and Switzerland. Eligible patients were aged 18-75 years with newly diagnosed high-risk Burkitt lymphoma without CNS involvement. Patients were randomly assigned to two cycles of R-CODOX-M/R-IVAC (R-CODOX-M: rituximab 375 mg/m2 on day 1 and 9, cyclophosphamide 800 mg/m2 on day 1, cyclophosphamide 200 mg/m2 on days 2-5, vincristine 1·5 mg/m2 on days 1 and 8, doxorubicin 40 mg/m2 on day 1, and methotrexate 3000 mg/m2 on day 10; R-IVAC: rituximab 375 mg/m2 on days 3 and 7, iphosphamide 1500 mg/m2 on days 1-5, etoposide 60 mg/m2 on days 1-5, and cytarabin 2000 mg/m2 on day 1 and 2) or six cycles of DA-EPOCH-R (dose-adjusted etoposide 50-124 mg/m2 on days 1-4, prednisolone 120 mg/m2 on days 1-5, vincristine 0·4 mg/m2 on days 1-4, dose-adjusted cyclophosphamide 480-1866 mg/m2 on day 5, dose-adjusted doxorubicin 10-24·8 mg/m2 on days 1-4, rituximab 375 mg/m2 on days 1 and 5). Patients older than 65 years received a dose modified R-CODOX-M/R-IVAC. All drugs were intravenous except for prednisolone, which was oral. Patients also received four intrathecal CNS administrations with cytarabin (70 mg) and four with methotrexate (15 mg). Patients were stratified by centre, leukemic disease, and HIV-positivity. The primary endpoint was progression-fee survival. All analyses were done by modified intention-to-treat, excluding randomly assigned patients who were subsequently found to have CNS involvement or diagnosis other than Burkitt lymphoma at study entry. This study is registered with the European Clinical Trial Register, EudraCT2013-004394-27.

FINDINGS

Due to a slow accrual, the study was closed prematurely on Nov 15, 2021. Between Aug 4, 2014, and Sept 17, 2021, 89 patients were enrolled and randomly assigned to receive R-CODOX-M/R-IVAC (n=46) or DA-EPOCH-R (n=43). Five patients were excluded after random assignment (three in the R-CODOX-M/R-IVAC group [one diagnosis other than Burkitt lymphoma at study entry according to local pathology and two CNS involvement] and two in the DA-EPOCH-R group [one diagnosis other than Burkitt lymphoma at study entry according to local pathology and one CNS involvement]. 84 remaining patients were included in the modified intention-to-treat analysis. 73 (87%) of 84 patients were male, 76 (90%) presented with stage III or IV disease, and nine (11%) had HIV-positive Burkitt lymphoma. Median patient age was 52 years (IQR 37-64). With a median follow-up of 28·5 months (IQR 13·2-43·7), 2-year progression-free survival was 76% (95% CI 60-86%) in the R-CODOX-M/R-IVAC group and 70% (54-82%) in the DA-EPOCH-R group (hazard ratio 1·42, 95% CI 0·63-3·18; p=0·40). There were two deaths in the R-CODOX-M/R-IVAC group (one infection [treatment related] and one due to disease progression [not treatment related]) and one death in the DA-EPOCH-R group (COVID-19 infection [treatment related]). In the R-CODOX-M/R-IVAC group, four patients went off-protocol because of toxic effects, versus none in the DA-EPOCH-R group. Patients treated with R-CODOX-M/R-IVAC had more infectious adverse events (24 [56%] of 43 patients had at least one grade 3-5 infection vs 14 [34%] of 41 patients in the DA-EPOCH-R group).

INTERPRETATION

The trial stopped early, but the available data suggest that while DA-EPOCH-R did not result in superior progression-free survival compared with R-CODOX-M/R-IVAC, it was associated with fewer toxic effects and need for supportive care. DA-EPOCH-R appears to be an additional valid therapeutic option for patients with high-risk Burkitt lymphoma without CNS involvement.

FUNDING

The Dutch Cancer Society and the Schumacher-Kramer Foundation.

Combined therapy with ibrutinib and bortezomib followed by ibrutinib maintenance in relapsed or refractory mantle cell lymphoma and high-risk features: a phase 1/2 trial of the European MCL network (SAKK 36/13)

Background

The Bruton's tyrosine kinase inhibitor ibrutinib and the proteasome inhibitor bortezomib have single-agent activity, non-overlapping toxicities, and regulatory approval in mantle cell lymphoma (MCL). In vitro, their combination provides synergistic cytotoxicity. In this investigator-initiated phase 1/2 trial, we established the recommended phase 2 dose of ibrutinib in combination with bortezomib, and assessed its efficacy in patients with relapsed or refractory MCL.

Methods

In this phase 1/2 study open in 15 sites in Switzerland, Germany and Italy, patients with relapsed or refractory MCL after ≤2 lines of chemotherapy and both ibrutinib-naïve and bortezomib-naïve received six cycles of ibrutinibb and bortezomib, followed by ibrutinib maintenance. For the phase 1 study, a standard 3 + 3 dose escalation design was used to determine the recommended phase 2 dose of ibrutinib in combination with bortezomib. The primary endpoint in phase 1 was the dose limiting toxicities in cycle 1. The phase 2 study was an open-label, single-arm trial with a Simon's two-stage min-max design, with a primary endpoint of overall response rate (ORR) assessed by CT/MRI. This study was registered with ClinicalTrials.gov, NCT02356458.

Findings

Between August 2015 and September 2016, nine patients were treated in the phase 1 study, and 49 patients were treated between November 2016 and March 2020 in the phase 2 of the trial. The ORR was 81.8% (90% CI 71.1, 89.8%, CR(u) 21.8%) which increased with continued ibrutinib (median 10.6 months) to 87.3%, (CR(u) 41.8%). 75.6% of patients had at least one high-risk feature (Ki-67 > 30%, blastoid or pleomorphic variant, p53 overexpression, TP53 mutations and/or deletions). In these patients, ibrutinib and bortezomib were also effective with an ORR of 74%, increasing to 82% during maintenance. With a median follow-up of 25.4 months, the median duration of response was 22.7, and the median PFS was 18.6 months. PFS reached 30.8 and 32.9 months for patients with a CR or Cru, respectively.

Interpretation

The combination of ibrutinib and bortezomib shows durable efficacy in patients with relapsed or refractory MCL, also in the presence of high-risk features.

Funding

SAKK (Hubacher Fund), Swiss State Secretariat for Education, Research and Innovation, Swiss Cancer Research Foundation, and Janssen.

Increased TIM-3 and galectin-9 serum levels in patients with advanced systemic mastocytosis

BACKGROUND

Systemic mastocytosis is characterized by expansion of clonal mast cells in various tissues. Several biomarkers with diagnostic and therapeutic potential have recently been characterized in mastocytosis, such as the serum marker tryptase and the immune checkpoint molecule PD-L1.

OBJECTIVE

We aimed to investigate whether serum levels of other checkpoint molecules are altered in systemic mastocytosis and whether these proteins are expressed in mastocytosis infiltrates in the bone marrow.

METHODS

Levels of different checkpoint molecules were analyzed in serum of patients with different categories of systemic mastocytosis and healthy controls and correlated to disease severity. Bone marrow biopsies from patients with systemic mastocytosis were stained to confirm expression.

RESULTS

Serum levels of TIM-3 and galectin-9 were increased in systemic mastocytosis, particularly in advanced subtypes, compared with healthy controls. TIM-3 and galectin-9 levels were also found to correlate with other biomarkers of systemic mastocytosis, such as serum tryptase and KIT D816V variant allele frequency in the peripheral blood. Moreover, we observed expression of TIM-3 and galectin-9 in mastocytosis infiltrates in bone marrow.

CONCLUSIONS

Together, our results demonstrate for the first time that serum levels of TIM-3 and galectin-9 are increased in advanced systemic mastocytosis. Moreover, TIM-3 and galectin-9 are expressed in bone marrow infiltrates in mastocytosis. These findings provide a rationale for exploring TIM-3 and galectin-9 as diagnostic markers and eventually therapeutic targets in systemic mastocytosis, particularly in advanced forms.

Emerging entities: high-grade/large B-cell lymphoma with 11q aberration, large B-cell lymphoma with IRF4 rearrangement, and new molecular subgroups in large B-cell lymphomas. A report of the 2022 EA4HP/SH lymphoma workshop

Emerging entities and molecular subgroups in large B-cell lymphomas (LBCLs) were discussed during the 2022 European Association for Haematopathology/Society for Hematopathology workshop in Florence, Italy. This session focused on newly recognized diseases and their diagnostic challenges. High-grade/large B-cell lymphoma with 11q aberration (HG/LBCL-11q) is defined by chromosome 11q-gains and telomeric loss. FISH analysis is recommended for the diagnosis. HG/LBCL-11q can occur in the setting of immunodeficiency, including ataxia-telangiectasia, and predominates in children. The morphological spectrum of these cases is broader than previously thought with often Burkitt-like morphology and coarse apoptotic bodies. It has a Burkitt-like immunophenotype (CD10+, BCL6+, BCL2-) but MYC expression is weak or negative, lacks MYC rearrangement, and is in contrast to Burkitt lymphoma 50% of the cases express LMO2. LBCL with IRF4 rearrangement (LBCL-IRF4) occurs mainly in the pediatric population but also in adults. LBCL-IRF4 has an excellent prognosis, with distinguishing molecular findings. IRF4 rearrangements, although characteristic of this entity, are not specific and can be found in association with other chromosomal translocations in other large B-cell lymphomas. Other molecular subgroups discussed included primary bone diffuse large B-cell lymphoma (PB-DLBCL), which has distinctive clinical presentation and molecular findings, and B-acute lymphoblastic leukemia (B-ALL) with IGH::MYC translocation recently segregated from Burkitt lymphoma with TdT expression. This latter disorder has molecular features of precursor B-cells, often tetrasomy 1q and recurrent NRAS and KRAS mutations. In this report, novel findings, recommendations for diagnosis, open questions, and diagnostic challenges raised by the cases submitted to the workshop will be discussed.

Follicular helper T-cell lymphomas: disease spectrum, relationship with clonal hematopoiesis, and mimics. A report of the 2022 EA4HP/SH lymphoma workshop

Follicular helper T-cell lymphomas (TFH lymphomas) were discussed in session V of the lymphoma workshop of the European Association for Haematopathology (EA4HP)/Society for Hematopathology (SH) 2022 meeting in Florence, Italy. The session focused on the morphologic spectrum of TFH lymphoma, including its three subtypes: angioimmunoblastic-type (AITL), follicular-type, and not otherwise specified (NOS). The submitted cases encompassed classic examples of TFH lymphoma and unusual cases such as those with early or indolent presentations, associated B-cell proliferations, or Hodgkin/Reed-Sternberg-like cells. The relationship between TFH lymphoma and clonal hematopoiesis was highlighted by several cases documenting divergent evolution of myeloid neoplasm and AITL from shared clonal mutations. The distinction between TFH lymphoma and peripheral T-cell lymphoma, not otherwise specified (PTCL, NOS), was stressed, and many challenging examples were presented. Various cases highlighted the difficulties of differentiating TFH lymphoma from other established types of lymphoma and reactive conditions. Cutaneous T-cell lymphoma expressing TFH markers, particularly when resulting in lymph node involvement, should be distinguished from TFH lymphomas. Additional immunophenotyping and next-generation sequencing studies were performed on various cases in this session, highlighting the importance of these technologies to our current understanding and classification of TFH lymphomas.

The many faces of nodal and splenic marginal zone lymphomas. A report of the 2022 EA4HP/SH lymphoma workshop

Session 3 of the lymphoma workshop of the XXI joint meeting of the European Association for Haematopathology and the Society for Hematopathology took place in Florence, Italy, on September 22, 2022. The topics of this session were splenic and nodal marginal zone lymphomas, transformation in marginal zone lymphomas, and pediatric nodal marginal zone lymphomas and their differential diagnosis as well as related entities. Forty-two cases in these categories were submitted to the workshop, including splenic lymphomas (marginal zone and diffuse red pulp lymphomas), transformed marginal zone lymphomas (splenic and nodal), nodal marginal zone lymphomas with increased TFH-cells, and pediatric nodal marginal zone lymphomas. The case review highlighted some of the principal problems in the diagnosis of marginal zone lymphomas, including the difficulties in the distinction between splenic marginal zone lymphoma, splenic diffuse red pulp lymphoma, and hairy cell leukemia variant/splenic B-cell lymphoma with prominent nucleoli which requires integration of clinical features, immunophenotype, and morphology in blood, bone marrow, and spleen; cases of marginal zone lymphoma with markedly increased TFH-cells, simulating a T-cell lymphoma, where molecular studies (clonality and mutation detection) can help to establish the final diagnosis; the criteria for transformation of marginal zone lymphomas, which are still unclear and might require the integration of morphological and molecular data; the concept of an overlapping spectrum between pediatric nodal marginal zone lymphoma and pediatric-type follicular lymphoma; and the distinction between pediatric nodal marginal zone lymphoma and "atypical" marginal zone hyperplasia, where molecular studies are mandatory to correctly classify cases.

Cavity-based lymphomas: challenges and novel concepts. A report of the 2022 EA4HP/SH lymphoma workshop

The 2022 European Association for Haematopathology/Society for Hematopathology lymphoma workshop session on cavity-based lymphomas included sixty-eight cases in seven sections. The disease entities discussed include primary effusion lymphomas (PEL), extracavitary primary effusion lymphomas and confounding entities (ECPEL), HHV8-negative B-lineage lymphomas-effusion based (EBV-negative, EBV-positive, and plasmablastic types), diffuse large B-cell lymphoma associated with chronic inflammation, fibrin-associated diffuse large B-cell lymphoma (FA-DLBCL), breast implant-associated anaplastic large cell lymphoma (BIA-ALCL), and other lymphomas presenting as an effusion. All entities above are discussed; however, three are delved into greater detail given the challenges with classification: ECPEL, HHV8-negative effusion-based lymphomas, and FA-DLBCL. Cases exemplifying the diagnostic difficulty in differentiating ECPEL from HHV8-positive diffuse large B-cell lymphoma and germinotropic lymphoproliferative disorder were discussed. The more recently recognized effusion-based HHV8-negative large B-cell lymphoma is explored, with several cases submitted raising the question if this subset should be carved out as a specific entity, and if so, what should be the refining diagnostic criteria. Case submissions to the FA-DLBCL section yielded one of the largest case series to date, including classic cases, cases furthering the discussion on disease sites and prognosis, as well as novel concepts to be considered in this entity. The 2022 EA4HP/SH workshop cases allowed for further confirmation of the characteristics of some of the more historically accepted cavity-based lymphomas, as well as further inquiry and debate on relatively new or evolving entities.

Cytotoxic peripheral T-cell lymphomas and EBV-positive T/NK-cell lymphoproliferative diseases: emerging concepts, recent advances, and the putative role of clonal hematopoiesis. A report of the 2022 EA4HP/SH lymphoma workshop

Cytotoxic peripheral T-cell lymphomas and EBV-positive T/NK-cell lymphoproliferative diseases were discussed at the 2022 European Association for Haematopathology/Society for Hematopathology lymphoma workshop held in Florence, Italy. This session focused on (i) primary nodal EBV-positive T and NK-cell lymphomas (primary nodal-EBV-TNKL), (ii) extranodal EBV-positive T/NK lymphoproliferative diseases (LPD) in children and adults, (iii) cytotoxic peripheral T-cell lymphomas, NOS (cPTCL-NOS), EBV-negative, and (iv) miscellaneous cases. Primary nodal-EBV-TNKL is a newly recognized entity which is rare, aggressive, and associated with underlying immune deficiency/immune dysregulation. All cases presented with lymphadenopathy but some demonstrated involvement of tonsil/Waldeyer's ring and extranodal sites. The majority of tumors are of T-cell lineage, and the most frequent mutations involve the epigenetic modifier genes, such as TET2 and DNMT3A, and JAK-STAT genes. A spectrum of EBV-positive T/NK LPD involving extranodal sites were discussed and highlight the diagnostic challenge with primary nodal-EBV-TNKL when these extranodal EBV-positive T/NK LPD cases demonstrate predominant nodal disease either at presentation or during disease progression from chronic active EBV disease. The majority of cPTCL-NOS demonstrated the TBX21 phenotype. Some cases had a background of immunosuppression or immune dysregulation. Interestingly, an unexpected association of cPTCL-NOS, EBV-positive and negative, with TFH lymphomas/LPDs was observed in the workshop cases. Similar to a published literature, the genetic landscape of cPTCL-NOS from the workshop showed frequent mutations in epigenetic modifiers, including TET2 and DNMT3A, suggesting a role of clonal hematopoiesis in the disease pathogenesis.

Genetic Factors in Familial Manifestation of Primary Mediastinal Large B-Cell Lymphoma over Two Generations

INTRODUCTION

Primary mediastinal large B-cell lymphoma (PMBL) is a rarely occurring lymphoid malignancy which typically affects young adults and presents itself as an anterior mediastinal mass. Gene expression profiling as well as somatic genetic analysis revealed that it is closely related to classical Hodgkin lymphoma, whereas morphologically, it tends to resemble diffuse large B-cell lymphoma. Familial clustering of PMBL is rare - only two reports have been published to date. While it is generally accepted that positive family history is associated with increased risk of developing a lymphoma, genetic risk factors which might predispose to PMBL are largely unknown.

CASE PRESENTATION

We performed germline and tumor genetic analyses by whole-exome sequencing and array-CGH of a family, in which the father and the son both developed a PMBL. Germline investigations of both affected patients and of their two unaffected family members have not been able to provide a single risk factor associated with lymphoma predisposition. In addition, genes that were previously implicated in increased risk for PMBL, namely MLL (KMT2A) and TIRAP, were found to be intact in all investigated family members. Somatic genetic investigations identified known as well as novel genetic aberrations in tumors of the affected subjects.

CONCLUSION

We conclude that predisposition to a PMBL might be inherited through a combination of low- or moderate-risk factors and provide a shortlist of the most likely selected candidates, which can be used in future studies.

Testicular Rosai-Dorfman disease clonally related to CMML - Case report and literature review

BACKGROUND

Rosai-Dorfman disease (RDD), a rare form of non-Langerhans cell histiocytosis with heterogenous clinical features, arises from precursor cells that give rise to cells of the histiocytic and monocytic lineages. An association with hematological neoplasms has been reported. Testicular RDD is rarely described, with only 9 reported cases in the literature. Genetic data to assess clonal relationships between RDD and other hematological neoplasms remain scarce. We describe an instance of testicular RDD against a background of chronic myelomonocytic leukemia (CMML), with genetic studies in both neoplasms.

CASE PRESENTATION

A 72-year-old patient with a history of CMML sought evaluation of growing bilateral testicular nodules. Solitary testicular lymphoma was suspected; orchidectomy was performed. The diagnosis of testicular RDD was established morphologically and confirmed immunohistochemically. Molecular analysis of testicular lesions and of archived patient bone marrow revealed the KRAS variant c 0.35 G>A / p.G12D in both, suggesting a clonal relationship.

CONCLUSION

These observations support classifying RDD as a neoplasm that can be clonally related to myeloid neoplasms.

Iron is a modifier of the phenotypes of JAK2-mutant myeloproliferative neoplasms

JAK 2-V617F mutation causes myeloproliferative neoplasms (MPNs) that can manifest as polycythemia vera (PV), essential thrombocythemia (ET), or primary myelofibrosis. At diagnosis, patients with PV already exhibited iron deficiency, whereas patients with ET had normal iron stores. We examined the influence of iron availability on MPN phenotype in mice expressing JAK2-V617F and in mice expressing JAK2 with an N542-E543del mutation in exon 12 (E12). At baseline, on a control diet, all JAK2-mutant mouse models with a PV-like phenotype displayed iron deficiency, although E12 mice maintained more iron for augmented erythropoiesis than JAK2-V617F mutant mice. In contrast, JAK2-V617F mutant mice with an ET-like phenotype had normal iron stores comparable with that of wild-type (WT) mice. On a low-iron diet, JAK2-mutant mice and WT controls increased platelet production at the expense of erythrocytes. Mice with a PV phenotype responded to parenteral iron injections by decreasing platelet counts and further increasing hemoglobin and hematocrit, whereas no changes were observed in WT controls. Alterations of iron availability primarily affected the premegakaryocyte-erythrocyte progenitors, which constitute the iron-responsive stage of hematopoiesis in JAK2-mutant mice. The orally administered ferroportin inhibitor vamifeport and the minihepcidin PR73 normalized hematocrit and hemoglobin levels in JAK2-V617F and E12 mutant mouse models of PV, suggesting that ferroportin inhibitors and minihepcidins could be used in the treatment for patients with PV.

[Classification of aggressive B-cell lymphomas : News and open questions]

The 5th edition of the WHO classification (WHO-HAEM5) and the International Consensus Classification (ICC) show a broad consensus in the categorization of aggressive, large B‑cell lymphomas with expected minor impact only on the daily diagnostic routine. The changes compared to the 2017 revised WHO-HAEM4R are moderate and include updated names of entities, sharpened diagnostic criteria, and upgrades from provisional to definite entities. The definition of the most common aggressive B‑cell lymphoma, diffuse large B‑cell lymphoma (DLBCL), not otherwise specified (NOS), remains unchanged, and both classifications strongly encourage subtyping into germinal center B‑like (GCB) or the activated B‑like (ABC or non-GCB) DLBCL. DLBCL, NOS, should be separated from other large B‑cell lymphomas including large B‑cell lymphoma with IRF4 rearrangement (upgraded to a definite entity in both classifications) and large-cell/high-grade B‑cell lymphomas with 11q aberration. Aggressive B‑cell lymphomas with MYC and BCL2 rearrangements form a molecularly distinct group and are listed as definite entities in both classifications. This is in contrast to the more heterogeneous group of aggressive B‑cell lymphomas with MYC and BCL6 rearrangements that are recognized as a provisional entity in the ICC, while they fall into the DLBCL, NOS, or the HGBL, NOS, groups in the WHO-HAEM5.