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He M, Zhou X, Wang X. Glycosylation: mechanisms, biological functions and clinical implications. Signal Transduct Target Ther 2024; 9:194. [PMID: 39098853 PMCID: PMC11298558 DOI: 10.1038/s41392-024-01886-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2023] [Revised: 05/25/2024] [Accepted: 06/07/2024] [Indexed: 08/06/2024] Open
Abstract
Protein post-translational modification (PTM) is a covalent process that occurs in proteins during or after translation through the addition or removal of one or more functional groups, and has a profound effect on protein function. Glycosylation is one of the most common PTMs, in which polysaccharides are transferred to specific amino acid residues in proteins by glycosyltransferases. A growing body of evidence suggests that glycosylation is essential for the unfolding of various functional activities in organisms, such as playing a key role in the regulation of protein function, cell adhesion and immune escape. Aberrant glycosylation is also closely associated with the development of various diseases. Abnormal glycosylation patterns are closely linked to the emergence of various health conditions, including cancer, inflammation, autoimmune disorders, and several other diseases. However, the underlying composition and structure of the glycosylated residues have not been determined. It is imperative to fully understand the internal structure and differential expression of glycosylation, and to incorporate advanced detection technologies to keep the knowledge advancing. Investigations on the clinical applications of glycosylation focused on sensitive and promising biomarkers, development of more effective small molecule targeted drugs and emerging vaccines. These studies provide a new area for novel therapeutic strategies based on glycosylation.
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Affiliation(s)
- Mengyuan He
- Department of Hematology, Shandong Provincial Hospital, Shandong University, Jinan, Shandong, 250021, China
| | - Xiangxiang Zhou
- Department of Hematology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong, 250021, China.
- National Clinical Research Center for Hematologic Diseases, the First Affiliated Hospital of Soochow University, Suzhou, 251006, China.
| | - Xin Wang
- Department of Hematology, Shandong Provincial Hospital, Shandong University, Jinan, Shandong, 250021, China.
- Department of Hematology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong, 250021, China.
- National Clinical Research Center for Hematologic Diseases, the First Affiliated Hospital of Soochow University, Suzhou, 251006, China.
- Taishan Scholars Program of Shandong Province, Jinan, Shandong, 250021, China.
- Branch of National Clinical Research Center for Hematologic Diseases, Jinan, Shandong, 250021, China.
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2
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Laurent C, Dietrich S, Tarte K. Cell cross talk within the lymphoma tumor microenvironment: follicular lymphoma as a paradigm. Blood 2024; 143:1080-1090. [PMID: 38096368 DOI: 10.1182/blood.2023021000] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Accepted: 11/30/2023] [Indexed: 03/22/2024] Open
Abstract
ABSTRACT Follicular lymphoma (FL) is an indolent yet incurable germinal center B-cell lymphoma retaining a characteristic follicular architecture. FL tumor B cells are highly dependent on direct and indirect interactions with a specific and complex tumor microenvironment (TME). Recently, great progress has been made in describing the heterogeneity and dynamics of the FL TME and in depicting how tumor clonal and functional heterogeneity rely on the integration of TME-related signals. Specifically, the FL TME is enriched for exhausted cytotoxic T cells, immunosuppressive regulatory T cells of various origins, and follicular helper T cells overexpressing B-cell and TME reprogramming factors. FL stromal cells have also emerged as crucial determinants of tumor growth and remodeling, with a key role in the deregulation of chemokines and extracellular matrix composition. Finally, tumor-associated macrophages play a dual function, contributing to FL cell phagocytosis and FL cell survival through long-lasting B-cell receptor activation. The resulting tumor-permissive niches show additional layers of site-to-site and kinetic heterogeneity, which raise questions about the niche of FL-committed precursor cells supporting early lymphomagenesis, clonal evolution, relapse, and transformation. In turn, FL B-cell genetic and nongenetic determinants drive the reprogramming of FL immune and stromal TME. Therefore, offering a functional picture of the dynamic cross talk between FL cells and TME holds the promise of identifying the mechanisms of therapy resistance, stratifying patients, and developing new therapeutic approaches capable of eradicating FL disease in its different ecosystems.
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Affiliation(s)
- Camille Laurent
- Department of Pathology, Institut Universitaire du Cancer de Toulouse Oncopole, Centre Hospitalo-Universitaire Toulouse, Centre de Recherches en Cancérologie de Toulouse, Laboratoire d'Excellence TOUCAN, INSERM Unité Mixte de Recherche 1037, Toulouse, France
| | - Sascha Dietrich
- Department of Haematology and Oncology, University Hospital Düsseldorf and Center for Integrated Oncology Aachen Bonn Cologne, Düsseldorf, Germany
| | - Karin Tarte
- Unité Mixte de Recherche S1236, INSERM, Université de Rennes, Etablissement Français du Sang Bretagne, Equipe Labellisée Ligue, Rennes, France
- Department of Biology, Centre Hospitalo-Universitaire de Rennes, Rennes, France
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3
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Stevenson FK, Forconi F. The essential microenvironmental role of oligomannoses specifically inserted into the antigen-binding sites of lymphoma cells. Blood 2024; 143:1091-1100. [PMID: 37992212 DOI: 10.1182/blood.2023022703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Revised: 10/27/2023] [Accepted: 10/29/2023] [Indexed: 11/24/2023] Open
Abstract
ABSTRACT There are 2 mandatory features added sequentially en route to classical follicular lymphoma (FL): first, the t(14;18) translocation, which upregulates BCL2, and second, the introduction of sequence motifs into the antigen-binding sites of the B-cell receptor (BCR), to which oligomannose-type glycan is added. Further processing of the glycan is blocked by complementarity-determining region-specific steric hindrance, leading to exposure of mannosylated immunoglobulin (Ig) to the microenvironment. This allows for interaction with the local lectin, dendritic cell-specific ICAM-3-grabbing nonintegrin (DC-SIGN), expressed by tissue macrophages and follicular dendritic cells. The major function of DC-SIGN is to engage pathogens, but this is subverted by FL cells. DC-SIGN induces tumor-specific low-level BCR signaling in FL cells and promotes membrane changes with increased adhesion to VCAM-1 via proximal kinases and actin regulators but, in contrast to engagement by anti-Ig, avoids endocytosis and apoptosis. These interactions appear mandatory for the early development of FL, before the acquisition of other accelerating mutations. BCR-associated mannosylation can be found in a subset of germinal center B-cell-like diffuse large B-cell lymphoma with t(14;18), tracking these cases back to FL. This category was associated with more aggressive behavior: both FL and transformed cases and, potentially, a significant number of cases of Burkitt lymphoma, which also has sites for N-glycan addition, could benefit from antibody-mediated blockade of the interaction with DC-SIGN.
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Affiliation(s)
- Freda K Stevenson
- School of Cancer Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom
| | - Francesco Forconi
- School of Cancer Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom
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4
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Coupland SE, Du MQ, Ferry JA, de Jong D, Khoury JD, Leoncini L, Naresh KN, Ott G, Siebert R, Xerri L. The fifth edition of the WHO classification of mature B-cell neoplasms: open questions for research. J Pathol 2024; 262:255-270. [PMID: 38180354 DOI: 10.1002/path.6246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Revised: 11/21/2023] [Accepted: 12/01/2023] [Indexed: 01/06/2024]
Abstract
The fifth edition of the World Health Organization Classification of Haematolymphoid Tumours (WHO-HAEM5) is the product of an evidence-based evolution of the revised fourth edition with wide multidisciplinary consultation. Nonetheless, while every classification incorporates scientific advances and aims to improve upon the prior version, medical knowledge remains incomplete and individual neoplasms may not be easily subclassified in a given scheme. Thus, optimal classification requires ongoing study, and there are certain aspects of some entities and subtypes that require further refinements. In this review, we highlight a selection of these challenging areas to prompt more research investigations. These include (1) a 'placeholder term' of splenic B-cell lymphoma/leukaemia with prominent nucleoli (SBLPN) to accommodate many of the splenic lymphomas previously classified as hairy cell leukaemia variant and B-prolymphocytic leukaemia, a clear new start to define their pathobiology; (2) how best to classify BCL2 rearrangement negative follicular lymphoma including those with BCL6 rearrangement, integrating the emerging new knowledge on various germinal centre B-cell subsets; (3) what is the spectrum of non-IG gene partners of MYC translocation in diffuse large B-cell lymphoma/high-grade B-cell lymphoma and how they impact MYC expression and clinical outcome; how best to investigate this in a routine clinical setting; and (4) how best to define high-grade B-cell lymphoma not otherwise specified and high-grade B-cell lymphoma with 11q aberrations to distinguish them from their mimics and characterise their molecular pathogenetic mechanism. Addressing these questions would provide more robust evidence to better define these entities/subtypes, improve their diagnosis and/or prognostic stratification, leading to better patient care. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.
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Affiliation(s)
- Sarah E Coupland
- Liverpool Clinical Laboratories, Liverpool University Hospitals Foundation Trust, Liverpool, UK
| | - Ming-Qing Du
- Department of Pathology, University of Cambridge, Cambridge, UK
| | - Judith A Ferry
- Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Daphne de Jong
- The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Joseph D Khoury
- Department of Pathology, Microbiology and Immunology, University of Nebraska Medical Center, Omaha, NE, USA
| | - Lorenzo Leoncini
- Department of Medical Biotechnology, University of Siena, Siena, Italy
| | - Kikkeri N Naresh
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, USA
| | - German Ott
- Department of Clinical Pathology, Robert-Bosch-Krankenhaus, and Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology, Stuttgart, Germany
| | - Reiner Siebert
- Institute of Human Genetics, Ulm University and Ulm University Medical Center, Ulm, Germany
| | - Luc Xerri
- Institut Paoli-Calmettes, CRCM and Aix-Marseille University, Marseille, France
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5
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Haebe S, Day G, Czerwinski DK, Sathe A, Grimes SM, Chen T, Long SR, Martin B, Ozawa MG, Ji HP, Shree T, Levy R. Follicular lymphoma evolves with a surmountable dependency on acquired glycosylation motifs in the B-cell receptor. Blood 2023; 142:2296-2304. [PMID: 37683139 PMCID: PMC10797552 DOI: 10.1182/blood.2023020360] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Revised: 08/15/2023] [Accepted: 08/16/2023] [Indexed: 09/10/2023] Open
Abstract
ABSTRACT An early event in the genesis of follicular lymphoma (FL) is the acquisition of new glycosylation motifs in the B-cell receptor (BCR) due to gene rearrangement and/or somatic hypermutation. These N-linked glycosylation motifs (N-motifs) contain mannose-terminated glycans and can interact with lectins in the tumor microenvironment, activating the tumor BCR pathway. N-motifs are stable during FL evolution, suggesting that FL tumor cells are dependent on them for their survival. Here, we investigated the dynamics and potential impact of N-motif prevalence in FL at the single-cell level across distinct tumor sites and over time in 17 patients. Although most patients had acquired at least 1 N-motif as an early event, we also found (1) cases without N-motifs in the heavy or light chains at any tumor site or time point and (2) cases with discordant N-motif patterns across different tumor sites. Inferring phylogenetic trees of the patients with discordant patterns, we observed that both N-motif-positive and N-motif-negative tumor subclones could be selected and expanded during tumor evolution. Comparing N-motif-positive with N-motif-negative tumor cells within a patient revealed higher expression of genes involved in the BCR pathway and inflammatory response, whereas tumor cells without N-motifs had higher activity of pathways involved in energy metabolism. In conclusion, although acquired N-motifs likely support FL pathogenesis through antigen-independent BCR signaling in most patients with FL, N-motif-negative tumor cells can also be selected and expanded and may depend more heavily on altered metabolism for competitive survival.
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Affiliation(s)
- Sarah Haebe
- Division of Oncology, Department of Medicine, Stanford University School of Medicine, Stanford, CA
| | - Grady Day
- Division of Oncology, Department of Medicine, Stanford University School of Medicine, Stanford, CA
| | - Debra K. Czerwinski
- Division of Oncology, Department of Medicine, Stanford University School of Medicine, Stanford, CA
| | - Anuja Sathe
- Division of Oncology, Department of Medicine, Stanford University School of Medicine, Stanford, CA
| | - Susan M. Grimes
- Stanford Genome Technology Center, Stanford University, Stanford, CA
| | - Tianqi Chen
- Division of Oncology, Department of Medicine, Stanford University School of Medicine, Stanford, CA
| | - Steven R. Long
- Department of Pathology, University of California, San Francisco, CA
- Department of Pathology, Stanford University School of Medicine, Stanford, CA
| | - Brock Martin
- Department of Pathology, Stanford University School of Medicine, Stanford, CA
| | - Michael G. Ozawa
- Department of Pathology, Stanford University School of Medicine, Stanford, CA
| | - Hanlee P. Ji
- Division of Oncology, Department of Medicine, Stanford University School of Medicine, Stanford, CA
| | - Tanaya Shree
- Division of Oncology, Department of Medicine, Stanford University School of Medicine, Stanford, CA
| | - Ronald Levy
- Division of Oncology, Department of Medicine, Stanford University School of Medicine, Stanford, CA
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6
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Kalmbach S, Grau M, Zapukhlyak M, Leich E, Jurinovic V, Hoster E, Staiger AM, Kurz KS, Weigert O, Gaitzsch E, Passerini V, Engelhard M, Herfarth K, Beiske K, Micci F, Möller P, Bernd HW, Feller AC, Klapper W, Stein H, Hansmann ML, Hartmann S, Dreyling M, Holte H, Lenz G, Rosenwald A, Ott G, Horn H. Novel insights into the pathogenesis of follicular lymphoma by molecular profiling of localized and systemic disease forms. Leukemia 2023; 37:2058-2065. [PMID: 37563306 PMCID: PMC10539171 DOI: 10.1038/s41375-023-01995-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 07/18/2023] [Accepted: 08/02/2023] [Indexed: 08/12/2023]
Abstract
Knowledge on the pathogenesis of FL is mainly based on data derived from advanced/systemic stages of FL (sFL) and only small cohorts of localized FL (lFL) have been characterized intensively so far. Comprehensive analysis with profiling of somatic copy number alterations (SCNA) and whole exome sequencing (WES) was performed in 147 lFL and 122 sFL. Putative targets were analyzed for gene and protein expression. Overall, lFL and sFL, as well as BCL2 translocation-positive (BCL2+) and -negative (BCL2-) FL showed overlapping features in SCNA and mutational profiles. Significant differences between lFL and sFL, however, were detected for SCNA frequencies, e.g., in 18q-gains (14% lFL vs. 36% sFL; p = 0.0003). Although rare in lFL, gains in 18q21 were associated with inferior progression-free survival (PFS). The mutational landscape of lFL and sFL included typical genetic lesions. However, ARID1A mutations were significantly more often detected in sFL (29%) compared to lFL (6%, p = 0.0001). In BCL2 + FL mutations in KMT2D, BCL2, ABL2, IGLL5 and ARID1A were enriched, while STAT6 mutations more frequently occurred in BCL2- FL. Although the landscape of lFL and sFL showed overlapping features, molecular profiling revealed novel insights and identified gains in 18q21 as prognostic marker in lFL.
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Affiliation(s)
- Sabrina Kalmbach
- Department of Clinical Pathology, Robert-Bosch Hospital, Stuttgart, Germany
- Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology, Stuttgart, Germany
- University of Tübingen, Tübingen, Germany
| | - Michael Grau
- Department of Medicine A, Department of Hematology, Oncology and Pneumology, University Hospital Münster, Münster, Germany
| | - Myroslav Zapukhlyak
- Department of Medicine A, Department of Hematology, Oncology and Pneumology, University Hospital Münster, Münster, Germany
| | - Ellen Leich
- Institute of Pathology, University of Würzburg and Comprehensive Cancer Center Main, Würzburg, Germany
| | - Vindi Jurinovic
- Department of Medicine III, University Hospital, LMU Munich, Munich, Germany
| | - Eva Hoster
- Department of Medicine III, University Hospital, LMU Munich, Munich, Germany
| | - Annette M Staiger
- Department of Clinical Pathology, Robert-Bosch Hospital, Stuttgart, Germany
- Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology, Stuttgart, Germany
- University of Tübingen, Tübingen, Germany
| | - Katrin S Kurz
- Department of Clinical Pathology, Robert-Bosch Hospital, Stuttgart, Germany
| | - Oliver Weigert
- Department of Medicine III, University Hospital, LMU Munich, Munich, Germany
| | - Erik Gaitzsch
- Department of Medicine III, University Hospital, LMU Munich, Munich, Germany
| | - Verena Passerini
- Department of Medicine III, University Hospital, LMU Munich, Munich, Germany
| | - Marianne Engelhard
- Department for Radiotherapy, University Hospital of Essen, Essen, Germany
| | - Klaus Herfarth
- Department of Radiation Oncology, University of Heidelberg, Heidelberg, Germany
| | - Klaus Beiske
- Department of Oncology, Oslo University Hospital, Oslo, Norway
- KG Jebsen center for B cell malignancies, Oslo, Norway
| | - Francesca Micci
- Section for Cancer Cytogenetics, Oslo University Hospital, Oslo, Norway
| | - Peter Möller
- Institute of Pathology, University Hospital Ulm, Ulm, Germany
| | | | | | - Wolfram Klapper
- Institute of Pathology, Hematopathology Section and Lymph Node Registry, University Hospital Schleswig-Holstein, Campus Kiel, Kiel, Germany
| | | | | | - Sylvia Hartmann
- Institute of Pathology, University Hospital Frankfurt, Frankfurt, Germany
| | - Martin Dreyling
- Department of Medicine III, University Hospital, LMU Munich, Munich, Germany
| | - Harald Holte
- KG Jebsen center for B cell malignancies, Oslo, Norway
| | - Georg Lenz
- Department of Medicine A, Department of Hematology, Oncology and Pneumology, University Hospital Münster, Münster, Germany
| | - Andreas Rosenwald
- Institute of Pathology, University of Würzburg and Comprehensive Cancer Center Main, Würzburg, Germany
| | - German Ott
- Department of Clinical Pathology, Robert-Bosch Hospital, Stuttgart, Germany.
- Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology, Stuttgart, Germany.
| | - Heike Horn
- Department of Clinical Pathology, Robert-Bosch Hospital, Stuttgart, Germany
- Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology, Stuttgart, Germany
- University of Tübingen, Tübingen, Germany
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7
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Salaverria I, Weigert O, Quintanilla-Martinez L. The clinical and molecular taxonomy of t(14;18)-negative follicular lymphomas. Blood Adv 2023; 7:5258-5271. [PMID: 37561599 PMCID: PMC10500559 DOI: 10.1182/bloodadvances.2022009456] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Revised: 07/11/2023] [Accepted: 08/09/2023] [Indexed: 08/12/2023] Open
Abstract
Follicular lymphoma (FL) is a neoplasm derived from germinal center B cells, composed of centrocytes and centroblasts, with at least a focal follicular growth pattern. The t(14;18) translocation together with epigenetic deregulation through recurrent genetic alterations are now recognized as the hallmark of FL. Nevertheless, FL is a heterogeneous disease, clinically, morphologically, and biologically. The existence of FL lacking the t(14;18) chromosomal alteration highlights the complex pathogenesis of FL, and indicates that there are alternative pathogenetic mechanisms that can induce a neoplasm with follicular center B-cell phenotype. Based on their clinical presentation, t(14;18)-negative FLs can be divided into 3 broad groups: nodal presentation, extranodal presentation, and those affecting predominantly children and young adults. Recent studies have shed some light into the genetic alterations of t(14;18)-negative FL. Within the group of t(14;18)-negative FL with nodal presentation, cases with STAT6 mutations are increasingly recognized as a distinctive molecular subgroup, often cooccurring with CREBBP and/or TNFRSF14 mutations. FL with BCL6 rearrangement shows clinicopathological similarities to its t(14;18)-positive counterpart. In contrast, t(14;18)-negative FL in extranodal sites is characterized mainly by TNFRSF14 mutations in the absence of chromatin modifying gene mutations. FL in children have a unique molecular landscape when compared with those in adults. Pediatric-type FL (PTFL) is characterized by MAP2K1, TNFRSF14, and/or IRF8 mutations, whereas large B-cell lymphoma with IRF4 rearrangement is now recognized as a distinct entity, different from PTFL. Ultimately, a better understanding of FL biology and heterogeneity should help to understand the clinical differences and help guide patient management and treatment decisions.
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Affiliation(s)
- Itziar Salaverria
- Institut d’Investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Cáncer, Madrid, Spain
| | - Oliver Weigert
- Laboratory for Experimental Leukemia and Lymphoma Research, Ludwig-Maximilians-University Hospital, Munich, Germany
- Department of Medicine III, Ludwig-Maximilians-University Hospital, Munich, Germany
| | - Leticia Quintanilla-Martinez
- Institute of Pathology and Neuropathology and Comprehensive Cancer Center Tübingen, University Hospital Tübingen, Eberhard-Karls University of Tübingen, Tübingen, Germany
- Cluster of Excellence iFIT “Image-guided and functionally Instructed Tumor therapies,” Eberhard-Karls University of Tübingen, Tübingen, Germany
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Follicular Lymphoma in the 5th Edition of the WHO-Classification of Haematolymphoid Neoplasms-Updated Classification and New Biological Data. Cancers (Basel) 2023; 15:cancers15030785. [PMID: 36765742 PMCID: PMC9913816 DOI: 10.3390/cancers15030785] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Revised: 01/23/2023] [Accepted: 01/24/2023] [Indexed: 01/31/2023] Open
Abstract
The conceptual description of Follicular lymphoma (FL) in the 5th edition of the World Health Organization (WHO) classification of haematolymphoid tumors (WHO-HAEM5) has undergone significant revision. The vast majority of FL (85%) with a follicular growth pattern are composed of centrocytes and centroblasts, harbor the t(14;18)(q32;q21) translocation and are now termed classic FL (cFL). They are set apart from three related subtypes, FL with predominantly follicular growth pattern, FL with unusual cytological features (uFL) and follicular large B-cell lymphoma (FLBCL). In contrast to the revised 4th edition of the WHO classification of haematolymphoid tumors (WHO-HAEM4R), grading of cFL is no longer mandatory. FL with a predominantly diffuse growth pattern had been previously recognized in WHO-HAEM4R. It frequently occurs as a large tumor in the inguinal region and is associated with CD23 expression. An absence of the IGH::BCL2 fusion and frequent STAT6 mutations along with 1p36 deletion or TNFRSF14 mutation is typical. The newly introduced subtype of uFL includes two subsets that significantly diverge from cFL: one with "blastoid" and one with "large centrocyte" variant cytological features. uFL more frequently displays variant immunophenotypic and genotypic features. FLBCL is largely identical to WHO-HAEM4R FL grade 3B and renaming was done for reasons of consistency throughout the classification. In-situ follicular B-cell neoplasm, pediatric-type FL, duodenal-type FL and primary cutaneous follicle center lymphoma are categorized as discrete entities. In addition, novel findings concerning underlying biological mechanisms in the pathogenesis of early and systemic follicular lymphoma will be presented.
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