Fifth Edition of the World Health Classification of Tumors of the Hematopoietic and Lymphoid Tissues: Mature T-cell, NK-cell and Stroma-Derived Neoplasms of Lymphoid Tissues.

This review focuses on mature T-cell, NK cell, and stroma-derived neoplasms in the 5th edition of the World Health Organization (WHO) classification of hematolymphoid tumors (WHO-HEM5), including changes from the revised 4th edition (WHO-HEM4R). Overall, information has expanded, primarily due to advancements in genomic understanding. The updated classification adopts a hierarchical format. The updated classification relies on a multidisciplinary approach, incorporating insights from a diverse group of pathologists, clinicians, and geneticists. Indolent NK-cell lymphoproliferative disorder of the gastrointestinal tract, EBV-positive nodal T- and NK-cell lymphoma, and several stroma-derived neoplasms of lymphoid tissues have been newly introduced or included. The review also provides guidance on how the WHO-HEM5 can be applied in routine clinical practice.

Fifth Edition of the World Health Organization Classification of Tumors of the Hematopoietic and Lymphoid Tissues: Acute Lymphoblastic Leukemias, Mixed-Phenotype Acute Leukemias, Myeloid/Lymphoid Neoplasms With Eosinophilia, Dendritic/Histiocytic Neoplasms, and Genetic Tumor Syndromes.

This manuscript represents a review of lymphoblastic leukemia/lymphoma (acute lymphoblastic leukemia/lymphoblastic lymphoma), acute leukemias of ambiguous lineage, mixed-phenotype acute leukemias, myeloid/lymphoid neoplasms with eosinophilia and defining gene rearrangements, histiocytic and dendritic neoplasms, and genetic tumor syndromes of the 5th edition of the World Health Organization Classification of Tumors of the Hematopoietic and Lymphoid Tissues. The diagnostic, clinicopathologic, cytogenetic, and molecular genetic features are discussed. The differences in comparison to the 4th revised edition of the World Health Organization classification of hematolymphoid neoplasms are highlighted.

Assessment for 11q and other chromosomal aberrations in large B-cell/high-grade B cell lymphomas of germinal center phenotype lacking BCL2 expression.

The WHO classifications of hematolymphoid malignancies have recognized several distinct entities within the large B cell lymphomas, including the more recently described high-grade B cell lymphoma with 11q aberration (HGBCL-11q). We utilized genomic array to assess for chromosome 11q abnormalities in a broad set of aggressive B cell lymphomas from 27 patients with a focus on younger adults. The findings suggest more frequent alterations of 11q in diffuse large B cell lymphoma (DLBCL)/HGBCL-GC BCL2-, in comparison to cases of Burkitt lymphoma (BL) or DLBCL-GC BCL2+, and confirm a low genomic complexity score of BL. Variability identified in patterns of 11q alterations suggests genomic array studies may afford value over FISH testing as we continue to understand HGBCL-11q as a distinct entity, and interrogate cases of DLBCL/HGBCL-GC BCL2-.

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

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

The 5th edition of the World Health Organization Classification of mature lymphoid and stromal tumors - an overview and update.

The purpose of this review is to give an overview on the conceptual framework and major developments of the upcoming 5th edition of the World Health Organization (WHO) Classification of Haematolymphoid tumours (WHO-HAEM5) and to highlight the most significant changes made in WHO-HAEM5 compared with the revised 4th edition (WHO-HAEM4R) of lymphoid and stromal neoplasms. The changes from the revised 4th edition include the reorganization of entities by means of a hierarchical system that is realized throughout the 5th edition of the WHO classification of tumors of all organ systems, a modification of nomenclature for some entities, the refinement of diagnostic criteria or subtypes, deletion of certain entities, and introduction of new entities. For the first time, tumor-like lesions, mesenchymal lesions specific to lymph node and spleen, and germline predisposition syndromes associated with the lymphoid neoplasms are included in the classification.

The fifth edition of the WHO classification of mature B-cell neoplasms: open questions for research.

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.

Fifth Edition of the World Health Classification of Tumors of the Hematopoietic and Lymphoid Tissue: Myeloid Neoplasms.

In this manuscript, we review myeloid neoplasms in the fifth edition of the World Health Organization classification of hematolymphoid tumors (WHO-HEM5), focusing on changes from the revised fourth edition (WHO-HEM4R). Disease types and subtypes have expanded compared with WHO-HEM4R, mainly because of the expansion in genomic knowledge of these diseases. The revised classification is based on a multidisciplinary approach including input from a large body of pathologists, clinicians, and geneticists. The revised classification follows a hierarchical structure allowing usage of family (class)-level definitions where the defining diagnostic criteria are partially met or a complete investigational workup has not been possible. Overall, the WHO-HEM5 revisions to the classification of myeloid neoplasms include major updates and revisions with increased emphasis on genetic and molecular drivers of disease. The most notable changes have been applied to the sections of acute myeloid leukemia and myelodysplastic neoplasms (previously referred to as myelodysplastic syndrome) with incorporation of novel, disease-defining genetic changes. In this review we focus on highlighting the updates in the classification of myeloid neoplasms, providing a comparison with WHO-HEM4R, and offering guidance on how the new classification can be applied to the diagnosis of myeloid neoplasms in routine practice.

Abnormal bone marrow findings in patients following treatment with chimeric antigen receptor-T cell therapy.

BACKGROUND: Bone marrow (BM) assessment after CAR-T cell immunotherapy infusion is not routinely performed to monitor adverse events such as cytopenias, hemophagocytic lymphohistiocytosis, or infections. Our institution has performed BM biopsies as part of CAR-T cell treatment protocols, encompassing pre- and post-treatment time points and during long-term follow-up. METHODS: We conducted a systematic retrospective review of BM abnormalities observed in samples from 259 patients following CAR-T cell immunotherapy. We correlated BM pathology findings with mortality, relapse/residual disease, and laboratory values. RESULTS: At a median of 35.5 days post-CAR-T infusion, 25.5% showed severe marrow hypocellularity, and 6.2% showed serous atrophy, and peripheral blood cytopenias corroborated these observations. Marrow features associated with reduced disease burden post-CAR-T infusion include increased lymphocytes seen in 16 patients and an increase of macrophages or granulomatous response seen in 25 patients. However, a 100-day landmark analysis also showed increased marrow histiocytes were associated with lower survival (median OS 6.0 vs. 21.4 months, p = .026), as was grade 2-3 marrow reticulin (18 patients) (median OS 12.5 vs. 24.2 months, p = .034). CONCLUSIONS: These data represent the first systematic observations of BM changes in patients receiving CAR-T cell immunotherapy.

Clinical Validation of FusionPlex RNA Sequencing and Its Utility in the Diagnosis and Classification of Hematologic Neoplasms.

Recurrent gene rearrangements result in gene fusions that encode chimeric proteins, driving the pathogenesis of many hematologic neoplasms. The fifth edition World Health Organization classification and International Consensus Classification 2022 include an expanding list of entities defined by such gene rearrangements. Therefore, sensitive and rapid methods are needed to identify a broad range of gene fusions for precise diagnosis and prognostication. In this study, we validated the FusionPlex Pan-Heme panel analysis using anchored multiplex PCR/targeted RNA next-generation sequencing for routine clinical testing. Furthermore, we assessed its utility in detecting gene fusions in myeloid and lymphoid neoplasms. The validation cohort of 61 cases demonstrated good concordance between the FusionPlex Pan-Heme panel and other methods, including chromosome analysis, fluorescence in situ hybridization, RT-PCR, and Sanger sequencing, with an analytic sensitivity and specificity of 95% and 100%, respectively. In an independent cohort of 28 patients indicated for FusionPlex testing, gene fusions were detected in 21 patients. The FusionPlex Pan-Heme panel analysis reliably detected fusion partners and patient-specific fusion sequences, allowing accurate classification of hematologic neoplasms and the discovery of new fusion partners, contributing to a better understanding of the pathogenesis of the diseases.

Introduction to the Fifth Edition of the World Health Organization Classification of Tumors of Hematopoietic and Lymphoid Tissues.

The World Health Organization (WHO) Classification of Tumors of Hematopoietic and Lymphoid Tissues has been the internationally accepted standard for over 20 years. The fifth edition of the WHO Classification (WHO-HEM5) is a multidisciplinary effort by pathologists, clinicians and other specialists that builds upon the revised fourth edition published in 2017. Entities in WHO-HEM5 are organized hierarchically. There are several changes in WHO-HEM5 from the previous edition, including addition of new entities, deletion of some entities and recognition or revision of some subtypes reflecting scientific developments and clinical advances during the past few years. Essential and desirable criteria for each entity are included. Here we introduce WHO-HEM5. Four reviews will follow that emphasize important aspects of the classification.

High-grade B-cell lymphoma, not otherwise specified: a multi-institutional retrospective study.

In this multi-institutional retrospective study, we examined the characteristics and outcomes of 160 patients with high-grade B-cell lymphoma, not otherwise specified (HGBL-NOS)-a rare category defined by high-grade morphologic features and lack of MYC rearrangements with BCL2 and/or BCL6 rearrangements ("double hit"). Our results show that HGBL-NOS tumors are heterogeneous: 83% of patients had a germinal center B-cell immunophenotype, 37% a dual-expressor immunophenotype (MYC and BCL2 expression), 28% MYC rearrangement, 13% BCL2 rearrangement, and 11% BCL6 rearrangement. Most patients presented with stage IV disease, a high serum lactate dehydrogenase, and other high-risk clinical factors. Most frequent first-line regimens included dose-adjusted cyclophosphamide, doxorubicin, vincristine, and etoposide, with rituximab and prednisone (DA-EPOCH-R; 43%); rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP; 33%); or other intensive chemotherapy programs. We found no significant differences in the rates of complete response (CR), progression-free survival (PFS), or overall survival (OS) between these chemotherapy regimens. CR was attained by 69% of patients. PFS at 2 years was 55.2% and OS was 68.1%. In a multivariable model, the main prognostic factors for PFS and OS were poor performance status, lactate dehydrogenase >3 × upper limit of normal, and a dual-expressor immunophenotype. Age >60 years or presence of MYC rearrangement were not prognostic, but patients with TP53 alterations had a dismal PFS. Presence of MYC rearrangement was not predictive of better PFS in patients treated with DA-EPOCH-R vs R-CHOP. Improvements in the diagnostic criteria and therapeutic approaches beyond dose-intense chemotherapy are needed to overcome the unfavorable prognosis of patients with HGBL-NOS.

Variant histology in nodular lymphocyte predominant Hodgkin lymphoma in an adult population: disease investigations and characteristics from a retrospective cohort.

A subset of variant histological patterns of nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL) has been associated with advanced disease stage and increased recurrence risk. Histopathology reports on core needle (CNB) and/or surgical excision biopsies (SEB) for 33 adult patients with NLPHL were examined for variant histology prevalence and association with disease stage and clinical outcome. Variant histological pattern was present in 13/33 patients (39%). Obtained tissue was inadequate for diagnosis in 1/23 (4.3%) cases of CNB. Variant histology was associated with stage IV disease at presentation (p<0.001). While SEB should be the procedure of choice in workup of patients for a diagnosis of NLPHL, CNB is an alternate option when SEB is contraindicated or difficult to undertake. Diagnostic reports should specifically note presence of variant histological patterns. Although late-stage disease was associated with progression or recurrence, overall prognosis is excellent for patients with NLPHL.