Maschinelle Lernverfahren (ML) haben in den letzten Jahren deutlich an Bedeutung gewonnen und sind heute ein fester Bestandteil der biomedizinischen Forschung. Sie unterstützen die Identifikation von Biomarkern und ermöglichen deren Kombination zu Vorhersagemodellen. Anders ausgedrückt: ML erlauben die effiziente Entwicklung von Biomarkersignaturen. In diesem Beitrag wird das Anwendungsspektrum von ML anhand ausgewählter Beispiele aus der Forschung an malignen Lymphomen veranschaulicht.

The clinical and molecular heterogeneity of diffuse large B cell lymphoma (DLBCL) is incompletely understood. By integrating proteomic, transcriptomic, and genomic data from 478 DLBCL tumors, we identify seven DLBCL proteogenotypes (PGs) reflecting specific pathophysiological features that span known molecular subtypes. PG4 is associated with poor outcome independent of established risk factors such as cell-of-origin, international prognostic index, or genetic features. PG4 contains activated B cell-like and germinal center B cell-like tumors and genetically unclassified cases. It shares a dark-zone-related B cell phenotype and shows enrichment for BTG1 mutations that can activate MYC. Single-cell sequencing and spatial transcriptomics reveal enhanced MYC and TCF3/4 transcriptional activity irrespective of MYC translocations. The PG4 tumor microenvironment is characterized by exhausted CD8+ T cells. Our study identifies common oncogenic themes underlying high-risk DLBCL tumors and provides a proteogenomic framework for future diagnostic and therapeutic approaches.

Burkitt lymphoma (BL) is an aggressive mature B-cell lymphoma that represents one of the most studied human malignancies. Initially described in equatorial Africa by the Irish surgeon Denis P. Burkitt, African (endemic) Burkitt lymphoma was the first human neoplasm shown to be associated with a virus, the Epstein-Barr virus (EBV), and also the first human neoplasm shown to harbor a recurrent chromosomal aberration, the t(8;14) (q24;q32) translocation that led to the identification of the central role of the MYC gene in tumorigenesis. In this review, we provide a brief historical introduction, followed by a presentation of important aspects of epidemiology, pathogenesis, and of diagnostic features including morphology, cytogenetics and molecular findings. We also provide a comprehensive overview of the findings convincingly demonstrating that subtyping of BL into EBV-positive and EBV-negative better describes the biological heterogeneity of this lymphoma entity than the historical subtyping into endemic, sporadic, and immunodeficiency-associated. As the distinction of BL from other B-cell lymphomas is important for providing optimal oncological care, we also discuss the differential diagnosis and how this lymphoma can be distinguished from other aggressive B-cell lymphomas.

Follicular lymphoma (FL) patients are at risk of disease transformation to aggressive high-grade lymphoma (tFL). While several genetic alterations have been implicated in tFL, the role of microenvironmental interactions and post-transcriptional regulation by non-coding RNAs remains poorly understood. We performed the first matched profiling of mRNAs and short non-coding RNAs (miRNAs) in paired FL and tFL samples (n = 11 pairs). This revealed differential expression of 1,075 mRNAs and 19 miRNAs, including repression of miR-29 family in tFL (miR-29a/b/c). Further analysis uncovered that MYC directly transcriptionally represses miR-29 in tFL, resulting in the upregulation of its target TRAF4. TRAF4 upregulation contributes to CD40 signaling being strongly activated in tFL and supports malignant B-cell proliferation. Notably, this increased CD40 pathway activity in 90% of tFL and contrasted with the reduced T-cell numbers in tFL niches. Thus, the MYC-miR-29-TRAF4 axis and increased CD40 signaling propensity may serve as tFL cells’ adaptation to reduced numbers of CD40L+ T-cells. Moreover, lower levels of all miR-29s(a/b/c) were associated with shorter overall survival (OS) and progression-free survival in FL (n = 185), including in a multivariate analysis. Low miR-29c was also associated with shorter OS in a validation cohort (n = 92) from the first-line R-CHOP therapy clinical trial (SWOG S0016, NCT00006721).

High-grade B-cell lymphoma, not otherwise specified (HGBCL, NOS), is defined by morphologic features intermediate between Burkitt lymphoma and diffuse large B-cell lymphoma (DLBCL). Lymphomas with a complex 11q aberration or concurrent MYC- and BCL2- or BCL6- rearrangements are excluded from this category. However, the reproducibility of the diagnosis of HGBCL, NOS is unknown to date. Expert hematopathologists of the Lymphoma/Leukemia Molecular Profiling Project reviewed 92 cases submitted as HGBCL, NOS. At least 3/4 hematopathologists reviewing cases independently confirmed the diagnosis in 30/92 (33%) cases, while 13 cases (14%) were reclassified as DLBCL. The remaining 49 cases were jointly reviewed by the consensus panel of 10 to 15 pathologists, confirming an additional 9 HGBCL, NOS. The remaining cases were reclassified as DLBCL or other aggressive B-cell lymphomas or were excluded due to insufficient material. In aggregate, only 39/92 (42%) of initially submitted cases were confirmed as HGBCL, NOS, demonstrating poor interobserver agreement. Interestingly, however, there were no significant differences between the initially submitted cohort and those ultimately confirmed by the pathology review panel concerning dark zone signature (DZsig) expression, frequency of MYC -rearrangements and cell of origin, among others. Despite the finding that pathologists can identify cytomorphological features associated with adverse biological characteristics, the poor reproducibility of high-grade morphology and molecular heterogeneity suggests that HGBCL, NOS does not represent a distinct clinicopathologic entity and that more objective markers of distinct biologic features, such as the DZsig, may better separate cases into relevant diagnostic categories than morphology alone.

PURPOSE:Targeting aberrantly activated kinases in pleural mesothelioma (PM) is a promising therapeutic strategy. To identify potential candidates, we characterized recurrent chromosomal gains in PM and subsequently evaluated the specific inhibition of kinases that were activated by amplification and/or overexpression. METHODS:42 primary PM were screened for chromosomal alterations using OncoScan technology and AKT expression was assessed using immunohistochemistry. The impact of Ipatasertib (pan-AKT inhibitor) and Sapanisertib (mTOR inhibitor) on cell survival, apoptosis induction, AKT/mTOR signaling, glycolysis was investigated in cell lines and primary cells. Preclinical anti-tumor efficacy was further assessed in a PDX model selected for AKT and mTOR expression. RESULTS:OncoScan profiling identified eleven regions of significant chromosomal gains. Among them, 14q32.33 and 19q13.2 gains affected AKT1 and AKT2, members of the AKT serine/threonine protein kinase family. AKT1 protein was expressed in 66 % (60/91), AKT2 in 80 % (73/91) and AKT3 in 94 % (86/91) PM. 57 % PM co-expressed AKT1/AKT2/AKT3. Treatment with Ipatasertib impaired cell viability in PM cell lines and induced apoptosis. Combined treatment with Ipatasertib and Sapanisertib had a synergistic cytotoxic effect in all three cell lines and primary cells from two PM patients, even in Cisplatin-resistant cells. We also noted an improved response to the combination in a PDX model. Mechanistically, the combined treatment acted synergistically to inactivate AKT/mTOR downstream signaling, suppress glycolysis, and trigger ATP depletion. CONCLUSIONS:Our study demonstrates recurrent activation of AKT kinases by copy number gains and upregulated expression in PM. Pharmacological AKT and mTOR inhibition is a promising therapeutic alternative for mesothelioma.

A small proportion of patients with acute promyelocytic leukemia (APL) harbor variant chromosomal translocations that lead to fusion of *RARA* to one of several alternative partner genes. The most frequently reported of variant is the t(11;17)(q23;q21), which generates the fusion of the zinc finger gene *ZBTB16* (formerly PLZF) to the *RARA* locus (*ZBTB16::RARA* fusion). This APL subtype is typically resistant to standard APL-directed therapies and most patients with this translocation relapse within one year with limited subsequent treatment options. Here, we report on a patient with *ZBTB16::RARA* APL who achieved durable molecular complete remission lasting more than two years after high-dose chemotherapy with busulfan and cyclophosphamide followed by autologous stem cell transplantation. This therapeutic approach has not previously been described for this rare APL variant and may represent a promising consolidation strategy in selected patients. PEER REVIEWED ARTICLE **Peer reviewers:** Prof. Dr Stefan Balabanov, Department of Medical Oncology and Hematology, University Hospital Zurich, Zurich, Switzerland Prof. Dr Alicia Rovó, Department of Hematology and Central Hematology Laboratory, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland Received on January 19, 2026; accepted after peer review on February 19, 2026; published online on February 23, 2026.

While allogeneic stem cell transplantation (alloSCT) remains the only curative option for patients with relapsed T-cell lymphoma, its place in the treatment algorithm of aggressive B-cell lymphoma is changing. This multicentre, prospective, investigator-initiated trial investigated the efficacy and toxicity of a myeloablative conditioning regimen comprising fludarabine, thiotepa, and cyclophosphamide (FTC) prior to alloSCT in patients with relapsed/refractory (r/r) aggressive B-cell or T-cell lymphoma. Among 60 patients, PFS at one and two years was 40% (95% CI 28-52) and 36% (95% CI 24-49), OS was 43% (95% CI 31-56) and 37% (95% CI 25-50), respectively, without significant differences between 42 patients with B-cell and 18 patients with T-cell lymphoma. The primary endpoint of the study defined as 1-year PFS of 50% was not met. The cumulative incidence of progression/relapse at two years was 34% (95% CI 19-49) for B- and 11% (95% CI 0-26) for T-cell patients. Cumulative incidence of NRM was 25% (95% CI 14-36) at day 100 and 35% (95% CI 23-47) at one year. Twelve patients who had failed CAR T-cell therapy (CART) had outcomes comparable to patients without prior CART. In T-cell lymphoma, relapse after alloSCT was notably low, reflecting a strong graft-versus-lymphomaeffect. In B-cell lymphomas, our data suggest that alloSCT can be effective after CART failure, with more than one-third of patients being in remission after two years. These findings support the continued use of alloSCT in patients with aggressive lymphomas. Substantial NRM observed after FTC calls for the continued search of better tolerated conditioning regimens.

Interdigitating dendritic cell sarcomas (IDCSs) are rare tumors that commonly arise in the hematopoietic system and rarely outside. The genetic drivers of IDCS carcinogenesis are unknown; therefore, therapeutic options are limited. We investigated somatic gene mutations and copy-number alterations (CNAs) in nine IDCSs arising in the lung by whole-exome sequencing (WES) paired with shallow whole-genome sequencing (sWGS). Using a panel of immunohistochemical markers, follicular dendritic sarcomas and Langerhans cell sarcomas were excluded, and inflammatory myofibroblastic tumors were excluded based on morphology. The Ki-67 score was used to stratify the tumors into low-grade (≤ 20%) and high-grade (> 20%) tumors. The main question addressed by the study was whether genetic aberrations can be identified in IDCSs and whether these are druggable. High-grade IDCSs showed a higher fraction of genome altered by CNA (48.42%) than low-grade IDCSs (18.15%) and tended to have greater tumor mutation burden (7.56 versus 0.88 mut/Mb; not significant). Heterogeneous gains on chromosome 17 were characteristic of almost all IDCS cases (eight of nine cases, 89%), independent of grade. CNA in cancer-actionable genes was independent of clinicopathological characteristics and included amplifications in EGFR, MYC, MDM4, ERBB2, CCNE1, and BRAF and losses in MTAP, CDKN2A, CDKN2B, MLH1, and VHL, as well as homozygous losses in SMAD2/4, ATM, and TP53. Somatic gene mutations in cancer-related genes were identified in seven of nine IDCSs. No common driver mutations were identified. The heterogeneous genetic landscape suggests a mixed etiology of IDCS carcinogenesis and genomic instability in high-grade tumors. Distinct druggable biomarkers have been identified in almost all tumors, providing novel therapeutic options. © 2026 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Mature aggressive B-cell lymphomas, such as Burkitt lymphoma (BL) and Diffuse large B-cell lymphoma (DLBCL), show variations in microRNA (miRNA) expression. The entity of High-grade B-cell lymphoma with 11q aberration (HGBCL-11q) shares several biological features with both BL and DLBCL but data on its miRNA expression profile are yet scarce. Hence, this study aims to analyze the potential differences in miRNA expression of HGBCL-11q compared to BL and DLBCL. We evaluated the expression profiles of 2083 miRNAs in 25 HGCBL-11q, 7 BL, 131 DLBCL, and tonsils using the HTG EdgeSeq miRNA whole transcriptome assay. Uniform manifold approximation and projection (UMAP) and differential gene expression analyses based on DESeq2 were carried out. UMAP analysis of miRNA expression did not reveal distinct groups among the studied lymphomas. However, differential gene expression investigations detected sets of overexpressed miRNAs in HGBCL-11q when compared to BL (miR-9-3p, miR-9-5p, miR-3919, miR-129-1-3p, miR-129-2-3p, miR-331-3p, miR-196b-5p, and miR-28-5p) and DLBCL (miR-3919, miR-1290, miR-4538, and miR-4791), respectively. Notably, miR-3919 showed heterogeneous but significantly higher expression (p-value < 0.001) in HGBCL-11q than in both, BL and DLBCL. We identified a group of differentially expressed miRNAs between HGBCL-11q vs. BL and DLBCL, with miR-3919 as the most commonly and recurrently overexpressed miRNA in HGBCL-11q.

Objectives Primary nodal marginal B-cell lymphoma (NMZL) is rare and histologically very variable. Its large-cell presentation is difficult to distinguish from nodal diffuse large B-cell lymphoma (nDLBCL) due to the absence of specific markers for nodal marginal zone lymphomas in general.Methods Using a comprehensive cohort of NMZLs and a control cohort of nDLBCLs, we conducted a methylome analysis on subgroups of both.Results The methylomes were strikingly different between the cohorts but unexpectedly homogeneous within the NMZL cohort. This allowed us to describe the morphologic spectrum of NMZL in all its value ranges. The considerable overlap in growth pattern and cytology of NMZL with nDLBCL was explored morphometrically, leading to an operational tool for separating both by a simple measurement of cell size and nuclear size. This was integrated in a hierarchical approach, including a scoring system for the parameter growth pattern, follicular colonization, follicular dendritic network, IgD expression, and Ki-67 rate, and led to a proposal for a classifier that we present here.Conclusions This methylome-based study extends the morphological spectrum of NMZL towards large cell morphology and offers a conventional way to distinguish it from nDLBCL.

We present a review of mature B-cell neoplasms as described in the fifth edition of the WHO classification of haematolymphoid tumours (WHO-HAEM5). Entities have expanded, and definitions are increasingly reliant on genomic and other technologies. However, the WHO-HAEM5 employs a hierarchical structure with family (class)-level definitions that group several specific entities. This approach enables the assignment of a family-level diagnosis when criteria for specific entities cannot be met due to resource constraints. To facilitate application in resource-limited settings, WHO-HAEM5 divides diagnostic criteria into 'essential' and desirable criteria for most entities. This review focuses on changes and updates in B-cell lymphoma classification, providing guidance on how to apply the WHO classification in resource-limited settings.

According to the 2022 World Health Organization Classification, high-grade B-cell lymphoma with 11q aberration (HGBCL-11q) is a MYC-negative lymphoma with 11q duplication and terminal deletion as specific chromosomal aberrations for this neoplasm. However, there is a growing number of reports defying this definition, describing cases with the co-occurrence of 11q aberration and MYC rearrangement (HGBCL-11q,MYCR). This research has 2 aims. First, to compare the unique HGBCL-11q,MYCR group of 9 cases with 26 HGBCL-11q cases on chromosomal, mutational, and clinicopathological levels. The second objective was to investigate the association of the new HGBCL-11q,MYCR group with HGBCL-11q and 2 other closely related MYC-positive aggressive lymphoma subtypes: Burkitt lymphoma (BL) (n = 17) and HGBCL, not otherwise specified with MYCR (n = 10). Genetic results were obtained by classical cytogenetics, fluorescence in situ hybridization, microarrays, and whole exome sequencing. In parallel histopathologic/immunohistochemical analyses (HP/IHC)with flow cytometry (FCM), in conjunction with clinical presentation and treatment outcomes, are presented. Our findings reveal that HGBCL-11q,MYCR exists as an independent nosologic entity, distinct from BL and HGBCL-11q at the cytogenetic, molecular, and clinicopathological levels, although it contains common features of both lymphoma subtypes. Common features with BL include following: MYCR with the immunoglobulin (Ig) genes, patterns of secondary chromosomal aberrations like dup(1q), del(17p), and high number of MYC and CCND3 mutations. Other BL features are: frequent extranodal abdominal presentation, morphology, germinal center B-cell-like cell of origin determined by IHC and FCM, immunophenotypical features such as MYC(+)/LMO2(-) detected by following flow cytometric features: CD45(+)weaker, more cases with CD43(+) and CD44(-) expression, only expression of IgD and IgM heavy chain, and CD38(+)higher overexpression, which correlates with MYCR assessed by FCM. Similarity to HGBCL-11q includes the existence of 11q aberration, presence of DDX3X, ETS1, GNA13, NFRKB, and KMT2D, and the lack of TCF3 and ID3 mutations. Additionally, frequent nodal and tonsillar presentation, morphology, germinal center B-cell-like cell of origin, and immunophenotypical features, including CD56(+) expression measured using FCM, are observed, which are associated with NCAM duplication/amplification on 11q, and pathogenesis not associated with Epstein-Barr virus infection. The distinctive chromosomal change of HGBCL-11q,MYCR was the gain or amplification of 3q29. Our cohort of patients with HGBCL-11q,MYCR had similar relapse-free survival to that of patients with HGBCL-11q and BL, if treated with BL-directed regimens.

Abstract: Molecular characterization of high-grade B-cell lymphoma, not otherwise specified (HGBCL-NOS), is hindered by its rarity, evolving definition, and poor diagnostic reproducibility. To address this challenge, we analyzed 92 HGBCL-NOS tumors collected across Lymphoma/Leukemia Molecular Profiling Project sites. Leveraging comparison cohorts of diffuse large B-cell lymphoma, NOS (DLBCL-NOS) and Burkitt lymphoma (BL), and molecular frameworks described in these entities, our analysis revealed a heterogenous molecular landscape, reminiscent of DLBCL-NOS but with an enrichment of BL features. By cell-of-origin classification, 59% were germinal center B-cell–like (GCB), and 25% were activated B-cell–like (ABC). LymphGen, a genetic classifier for DLBCL-NOS, assigned a genetic subtype to 34% of HGBCL-NOS. Although classification rate was lower than in DLBCL-NOS (66%), assigned subtypes spanned the spectrum of LymphGen classes, including 31% of ABCs classified as MCD. Features differentiating HGBCL-NOS from DLBCL-NOS included MYC rearrangement (47% vs 6%); dark zone signature (DZsig) expression (45% vs 7%); and more frequent mutation of ID3, MYC, CCND3, and TP53, all common to BL. A genetic classifier that differentiates DLBCL-NOS from BL classified 53% of DZsig+ tumors as BL-like, and those classified as DLBCL-like were frequently BCL2-rearranged. Among DZsig− GCB tumors, 95% were DLBCL-like. Centralized pathology review reclassified almost half of tumors as DLBCL-NOS but did not identify a more homogenous HGBCL-NOS population, with no difference in features between confirmed and reclassified tumors. In conclusion, molecular testing enables a subset of HGBCL-NOS to be assigned to established categories. Based on rarity and diagnostic challenges, broader inclusion of HGBCL-NOS should be considered in biomarker-driven DLBCL trials.

Terminal deoxynucleotidyl transferase (TdT) is occasionally expressed in large B-cell lymphoma (LBCL), and this causes difficulty in differential diagnosis from B-lymphoblastic leukaemia/lymphoma (B-ALL/LBL). We reviewed 31 cases of TdT-positive LBCL and B-ALL/LBL, and their final diagnosis included 19 diffuse large/high-grade BCLs with MYC and BCL2 rearrangements (five DLBCL-MYC/BCL2, 14 HGBCL-MYC/BCL2), three DLBCL not otherwise specified (NOS), three HGBCL-NOS, four B-ALL/LBL, and two unclassifiable cases. TdT was variably expressed in all these cases, without any clear demarcation among different groups. Loss or partial loss of CD20 expression was seen in 13/17 DLBCL/HGBCL-MYC/BCL2, 2/3 HGBCL-NOS, and 2/2 unclassified, albeit not in DLBCL-NOS. Expression of BCL6 and/or MUM1 was seen in 3/4 B-ALL/LBLs and 2/2 unclassified. Next-generation sequencing revealed characteristic mutations associated with follicular lymphoma and its high-grade transformation in each DLBCL/HGBCL-MYC/BCL2, and also frequent variants in genes targeted by somatic hypermutation (SHM) in almost all DLBCL/HGBCL-MYC/BCL2, DLBCL-NOS, and HGBCL-NOS but one case. In contrast, such mutations were absent in B-ALL/LBL. There were no pathognomonic mutations in the two unclassifiable cases, although one showed a moderate level of somatic mutations in its rearranged IGHV. Furthermore, in three cases of TdT-positive HGBCL-MYC/BCL2, studies of previous or concurrent follicular lymphoma demonstrated their divergent evolution from an IGH::BCL2-positive cell population following acquisition of MYC translocation. In conclusion, mutation profiling analysis including the SHM target genes is highly valuable in the differential diagnosis between TdT-positive LBCL and B-ALL/LBL. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.