New concepts in EBV-associated B, T, and NK cell lymphoproliferative disorders

A differential diagnosis method for systemic CAEBV and the prospect of EBV-related immune cell markers via flow cytometry

Chronic active Epstein-Barr virus (CAEBV) infection of the T-cell or Natural killer (NK)-cell type, systemic form (systemic CAEBV or sCAEBV) was defined by the WHO in 2017 as an EBV-related lymphoproliferative disorder and is listed as an EBV-positive T-cell and NK-cell proliferation. The clinical manifestations and prognoses are heterogeneous. This makes systemic CAEBV indistinguishable from other EBV-positive T-cell and NK-cell proliferations. Early diagnosis of systemic CAEBV and early hematopoietic stem cell transplantation can improve patient prognosis. At present, the diagnosis of systemic CAEBV relies mainly on age, clinical manifestations, and cell lineage, incurring missed diagnosis, misdiagnosis, long diagnosis time, and inability to identify high-risk systemic CAEBV early. The diagnostic methods for systemic CAEBV are complicated and lack systematic description. The recent development of diagnostic procedures, including molecular biological and immunological techniques such as flow cytometry, has provided us with the ability to better understand the proliferation of other EBV-positive T cells and NK cells, but there is no definitive review of their value in diagnosing systemic CAEBV. This article summarizes the recent progress in systemic CAEBV differential diagnosis and the prospects of flow cytometry.

Hematopoietic Neoplasms of the Sinonasal Tract

Hematologic malignancies are one of the more common neoplasms to occur in the sinonasal tract and include a wide range of entities, including mature and immature B cell and T cell neoplasms as well as plasma cell dyscrasias and histiocytic disorders. CD45 expression can be helpful in identifying many, but not all, hematopoietic neoplasms in the sinonasal tract, and more extensive immunophenotyping, including EBV in situ hybridization, as well as correlation with genetic results and clinical features may be required for diagnosis.

A Rare Case of Systemic Epstein-Barr Virus-Positive Diffuse Large B-Cell Lymphoma With Hemophagocytic Lymphohistiocytosis in an Immunocompetent Young Man: Potential Diagnostic Pitfall and Therapeutic Challenge

Epstein-Barr virus-positive diffuse large B-cell lymphoma (EBV+ DLBCL) is an uncommon subtype of aggressive B-cell lymphoma, with both nodal and extranodal involvement being exceedingly rare. We present a unique case of a 32-year-old immunocompetent male with a nasopharynx lesion accompanied by fever and bilateral cervical lymphadenopathy. The initial biopsy from the nasopharynx proposed infectious mononucleosis (IM) as a potential diagnostic pitfall. The further discovery of lymph node and intestinal mucosa biopsies confirmed the diagnosis of systemic EBV+ DLBCL. After receiving four cycles of rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) treatment, the patient got complete remission. However, hemophagocytic lymphohistiocytosis (HLH) developed following the fifth cycle of CHOP. The patient accepted allogeneic hematopoietic stem cell transplantation (allo-HCT) subsequently. Unfortunately, the survival time was only 14 months. Appeals for a multi-dimension approach to understanding more fully and improving the outcomes of such cases are underscored.

Recurrent oral and nasopharyngeal ulcers, facial erythema, vesicles and scars in an older woman

A 71-year-old woman presented with a 30-year history of recurrent fever, fatigue, oral and nasopharyngeal ulcers, facial oedematous erythema and vesicles that ulcerated and healed by forming scars.

Insight into structural properties of viral G protein-coupled receptors and their role in the viral infection: IUPHAR Review 41

G protein-coupled receptors (GPCRs) are pivotal in cellular signalling and drug targeting. Herpesviruses encode GPCRs (vGPCRs) to manipulate cellular signalling, thereby regulating various aspects of the virus life cycle, such as viral spreading and immune evasion. vGPCRs mimic host chemokine receptors, often with broader signalling and high constitutive activity. This review focuses on the recent advancements in structural knowledge about vGPCRs, with an emphasis on molecular mechanisms of action and ligand binding. The structures of US27 and US28 from human cytomegalovirus (HCMV) are compared to their closest human homologue, CX3CR1. Contrasting US27 and US28, the homotrimeric UL78 structure (HCMV) reveals more distance to chemokine receptors. Open reading frame 74 (ORF74; Kaposi's sarcoma-associated herpesvirus) is compared to CXCRs, whereas BILF1 (Epstein-Barr virus) is discussed as a putative lipid receptor. Furthermore, the roles of vGPCRs in latency and lytic replication, reactivation, dissemination and immune evasion are reviewed, together with their potential as drug targets for virus infections and virus-related diseases.

From the midfacial destructive drama to the unfolding EBV story: a short history of EBV-positive NK-cell and T-cell lymphoproliferative diseases

Epstein-Barr virus (EBV) is a ubiquitous gammaherpesvirus that has been related to oncogenesis of lymphoid and epithelial malignancies. Although the mechanism of EBV infection of NK and T cells remains enigmatic, it plays a pathogenic role in various EBV+ NK-cell and T-cell lymphoproliferative diseases (LPDs), through promotion of cell activation pathways, inhibition of cell apoptotic pathways, behaving as oncogenes, interacting with host oncogenes or acting epigenetically. The study of NK-cell LPDs, previously hampered by the lack of immunophenotypical and genotypical criteria of NK cells, has become feasible with the recently accepted criteria. EBV+ NK- and T-cell LPDs are mostly of poor prognosis. This review delivers a short history from primeval to recent EBV+ NK- and T-cell LPDs in non-immunocompromised subjects, coupled with increasing interest, and work on the biological and oncogenic roles of EBV.

Clinicopathologic Spectrum of Pediatric Posttransplant Lymphoproliferative Diseases Following Solid Organ Transplant

CONTEXT.—

Posttransplant lymphoproliferative disorder (PTLD) remains a significant complication in pediatric patients undergoing solid organ transplant (SOT). The majority involve Epstein-Barr virus (EBV)-driven CD20+ B-cell proliferations, which respond to reduction of immunosuppression and anti-CD20-directed immunotherapy. Owing to the low overall incidence, prospective studies of pediatric PTLD are scarce, leading to a lack of comprehensive understanding of this disorder in pediatric populations. This review aims to bridge this knowledge gap by providing a comprehensive analysis of the clinical, morphologic, and molecular genetic features of PTLD in children, adolescents, and young adults after SOT.

OBJECTIVE.—

To examine the clinical features, pathogenesis, and classification of pediatric PTLDs after SOT.

DATA SOURCES.—

Personal experiences and published works in PubMed.

CONCLUSIONS.—

PTLD includes a broad and heterogeneous spectrum of disorders, ranging from nonmalignant lymphoproliferations to lymphomas. While most pediatric PTLDs are EBV+, an increasing number of EBV- PTLDs have been recognized. The pathologic classification of PTLDs has evolved in recent decades, reflecting advancements in understanding the underlying pathobiology. Nevertheless, there remains a great need for further research to elucidate the biology, identify patients at higher risk for aggressive disease, and establish optimal treatment strategies for relapsed/refractory disease.

Enhancing diagnostic precision in EBV-related HLH: a multifaceted approach using 18F-FDG PET/CT and nomogram integration

BACKGROUND

The hyperinflammatory condition and lymphoproliferation due to Epstein-Barr virus (EBV)-associated hemophagocytic lymphohistiocytosis (HLH) affect the detection of lymphomas by 18F-FDG PET/CT. We aimed to improve the diagnostic capabilities of 18F-FDG PET/CT by combining laboratory parameters.

METHODS

This retrospective study involved 46 patients diagnosed with EBV-positive HLH, who underwent 18F-FDG PET/CT before beginning chemotherapy within a 4-year timeframe. These patients were categorized into two groups: EBV-associated HLH (EBV-HLH) (n = 31) and EBV-positive lymphoma-associated HLH (EBV + LA-HLH) (n = 15). We employed multivariable logistic regression and regression tree analysis to develop diagnostic models and assessed their efficacy in diagnosis and prognosis.

RESULTS

A nomogram combining the SUVmax ratio, copies of plasma EBV-DNA, and IFN-γ reached 100% sensitivity and 81.8% specificity, with an AUC of 0.926 (95%CI, 0.779-0.988). Importantly, this nomogram also demonstrated predictive power for mortality in EBV-HLH patients, with a hazard ratio of 4.2 (95%CI, 1.1-16.5). The high-risk EBV-HLH patients identified by the nomogram had a similarly unfavorable prognosis as patients with lymphoma.

CONCLUSIONS

The study found that while 18F-FDG PET/CT alone has limitations in differentiating between lymphoma and EBV-HLH in patients with active EBV infection, the integration of a nomogram significantly improves the diagnostic accuracy and also exhibits a strong association with prognostic outcomes.

Fifth Edition of the World Health Organization 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 cells, natural killer (NK) cells, and stroma-derived neoplasms in the fifth edition of the World Health Organization classification of hematolymphoid tumors, including changes from the revised fourth edition. 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, Epstein-Barr virus-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 fifth edition of the World Health Organization classification of hematolymphoid tumors can be applied in routine clinical practice.

Highly sensitive detection of Epstein-Barr virus-infected cells by EBER flow FISH

When Epstein-Barr virus (EBV) infection is suspected, identification of infected cells is important to understand the pathogenesis, determinine the treatment strategy, and predict the prognosis. We used the PrimeFlow™ RNA Assay Kit with a probe to detect EBV-encoded small RNAs (EBERs) and multiple surface markers, to identify EBV-infected cells by flow cytometry. We analyzed a total of 24 patients [11 with chronic active EBV disease (CAEBV), 3 with hydroa vacciniforme lymphoproliferative disorder, 2 with X-linked lymphoproliferative disease type 1 (XLP1), 2 with EBV-associated hemophagocytic lymphohistiocytosis, and 6 with posttransplant lymphoproliferative disorder (PTLD)]. We compared infected cells using conventional quantitative PCR methods and confirmed that infected cell types were identical in most patients. Patients with CAEBV had widespread infection in T and NK cells, but a small amount of B cells were also infected, and infection in patients with XLP1 and PTLD was not limited to B cells. EBV-associated diseases are believed to be complex pathologies caused by EBV infecting a variety of cells other than B cells. We also demonstrated that infected cells were positive for HLA-DR in patients with CAEBV. EBER flow FISH can identify EBV-infected cells with high sensitivity and is useful for elucidating the pathogenesis.

Mature B, T and NK-cell, plasma cell and histiocytic/dendritic cell neoplasms: classification according to the World Health Organization and International Consensus Classification

In 2022, two updated classification systems for lymphoid neoplasms were published by the World Health Organization (WHO Classification of Haematolymphoid Tumours, 5th edition, referred to hereafter as WHO-HAEM5) and the International Consensus Conference (ICC) (Alaggio et al. in Leukemia 36(7):1720-1748, 2022; Campo et al. in Blood 140(11):1229-1253, 2022). Both classifications were conceived by both pathologists and clinicians with expertise in the field. The reasons for this have been reviewed previously (Arber et al. in Virchows Arch 482(1):1-9, 2023; Cree in Leukemia 36(7):1701-1702, 2022, Leukemia 36(11):2750, 2022). Given that both groups were using data-driven processes and consensus and used the revised 4th edition of the WHO Classification of Haematolymphoid Tumours (WHO-HAEM4R) as a starting point, it is not entirely surprising that the resulting classifications are quite similar. However, they are not identical and reflect preferences or approaches for certain unsettled areas as well as preferred terminology. In this review, we will compare nomenclature of the WHO-HAEM5 and ICC classifications, focusing on lymphoid neoplasms and lymphoproliferative disorders (LPDs).

Clinical epidemiology of Epstein-Barr virus-associated Lymphoproliferative Disorders (EBV-LPDs) in hospitalized children: A six-year multi-institutional study in China

BACKGROUND

Epstein-Barr virus-associated lymphoproliferative disorders (EBV-LPDs) are a group of disorders involving lymphoid tissues or lymphocytes. The epidemiology and economic burden of hospitalized children with EBV-LPDs in China have not been well studied. This study aimed to reveal the epidemic characteristics and disease burden of EBV-LPDs among the Chinese hospitalized children, providing strategies for the prevention and management.

METHODS

This study was based on the FUTang Updating medical REcords (FUTURE) database of China and collected the medical records from 27 tertiary children's hospitals between January 2016 and December 2021 in China, counting five types of EBV-LPDs, namely EBV-positive T-cell lymphoproliferative disease, NK/T cell lymphoma, extranodal NK/T-cell lymphoma (nasal type), systemic EBV-positive T-cell lymphoproliferative disease of childhood and posttransplant lymphoproliferative disorders. We conducted a retrospective syhthesis and analysis of the epidemiological characteristics, expenses, length of stay (LOS), as well as complications among hospitalized children diagnosed with five types of EBV-LPDs and compared parameters using appropriate statistical tests.

RESULTS

The study described 153 children aged 0-18 years hospitalized with EBV-LPDs from 2016 to 2021 in the FUTURE database. The male-to-female ratio was 1.10:1, and more than half of the age distribution was in the 6-12 y group. Among EBV-LPDs cases, EBV+ T-LPD accounted for the largest proportion (65.36%). Complications were presented in 93 children with EBV-LPDs, mainly hemophagocytic lymphohistiocytosis (HLH). The median LOS of NKTL was 26.5 days [interquartile range (IQR) = 3-42], which was the longest among EBV-LPDs. The median hospitalization cost of PTLD was 10 785.74 United States dollars (IQR = 7 329.38-16 531.18), which was the heaviest among EBV-LPDs.

CONCLUSIONS

Compared with the total number of hospitalized children in China during the same period and in the same age group, the proportion of EBV-LPD is very low. EBV-LPD can develop in all age groups, but it is more common in school-age children. Among 5 EBV-LPDs, the disease with the highest proportion is EBV+ T-LPD. The overall disease burden of EBV-LPD was heavy, especially the economic burden. HLH was one of the most common complications, which could directly affect the burden of patients because of prolonged hospitalization. These data are taken from a very large database, illustrating the epidemiological and economic burden of EBV-LPDs hospitalized children in China, which enriched the existing epidemiological and disease burden content of EBV-LPDs.

Epstein-Barr virus-related lymphoproliferative disorders of the skin

Epstein Barr Virus (EBV) is associated both solid (nasopharyngeal carcinoma, non-nasopharyngeal lymphoepithelioma-like carcinoma, gastric carcinoma, leiomyosarcoma) and hematolymphoid malignancies, some of the latter, however, spanning over a spectrum ranging from reactive and self-limiting to severe and life-threatening conditions. This review will focus on the disorder most commonly involving the skin, namely: EBV-positive mucocutaneous ulcer; lymphomatoid granulomatosis; EBV-positive diffuse large B cell lymphoma; plasmablastic lymphoma; post-transplant lymphoproliferative disorder; extranodal NK/T cell lymphoma, nasal type; angoimmunoblastic T cell lymphoma; severe mosquito bite allergy; hydroa vacciniformelike lymphoproliferative disorder. Given the uncommon occurrence of all these infiltrates in the skin, multidisciplinary approach, as well as referral to tertiary care centers are always advisable.

Lymphocytes in Patients with Chronic Active Epstein-Barr Virus Disease Exhibited Elevated PD-1/PD-L1 Expression and a Prevailing Th2 Immune Response

Background And Objectives

Chronic active Epstein-Barr virus disease (CAEBV) is a proliferative disease of EBV+ T or natural killer (NK) cells with an unclear pathogenesis. This study aimed to examine the frequency and exhaustion levels of lymphocyte subsets in patients with CAEBV to further investigate the pathogenesis.

Methods

Using flow cytometry, we detected the frequency, expression levels of programmed cell death 1 (PD-1) and programmed death ligand 1 (PD-L1), and EBV infection status of peripheral T subsets and NK cells in patients with CAEBV and healthy individuals.

Results

24 patients and 15 healthy individuals were enrolled in this study. Patients showed notably higher expression levels of PD-1 and PD-L1 in peripheral T subsets and NK cells compared to healthy individuals (P < 0.05). EBV+ lymphocytes exhibited significantly higher PD-L1 expression levels than EBV- lymphocytes. Additionally, the frequency of effector memory T (Tem) cells was significantly increased in patients, and the PD-L1 expression level was positively correlated with the EBV load. Besides, helper T cell 2 (Th2) immune bias, also favoring EBV amplification, was found in patients, including increased Th2 cell frequency, enhanced response capacity, and elevated serum levels of associated cytokines. The distribution and PD-1 expression levels of peripheral T subsets returned to normal in patients who responded to PD-1 blockade therapy.

Conclusions

The up-regulation of the PD-1/PD-L1 pathway of peripheral T and NK cells and Th2 immune predominance jointly promoted EBV replication and the development of CAEBV. PD-1 blockade therapy reduced the PD-1 expression level of lymphocytes and helped normalize the distribution of the T subsets.

Diverse and reprogrammable mechanisms of malignant cell transformation in lymphocytes: pathogenetic insights and translational implications

While normal B- and T-lymphocytes require antigenic ligands to become activated via their B- and T-cell receptors (BCR and TCR, respectively), B- and T-cell lymphomas show the broad spectrum of cell activation mechanisms regarding their dependence on BCR or TCR signaling, including loss of such dependence. These mechanisms are generally better understood and characterized for B-cell than for T-cell lymphomas. While some lymphomas, particularly the indolent, low-grade ones remain antigen-driven, other retain dependence on activation of their antigen receptors seemingly in an antigen-independent manner with activating mutations of the receptors playing a role. A large group of lymphomas, however, displays complete antigen receptor independence, which can develop gradually, in a stepwise manner or abruptly, through involvement of powerful oncogenes. Whereas some of the lymphomas undergo activating mutations of genes encoding proteins involved in signaling cascades downstream of the antigen-receptors, others employ activation mechanisms capable of substituting for these BCR- or TCR-dependent signaling pathways, including reliance on signaling pathways physiologically activated by cytokines. Finally, lymphomas can develop cell-lineage infidelity and in the extreme cases drastically rewire their cell activation mechanisms and engage receptors and signaling pathways physiologically active in hematopoietic stem cells or non-lymphoid cells. Such profound reprograming may involve partial cell dedifferentiation or transdifferentiation towards histocytes, dendritic, or mesodermal cells with various degree of cell maturation along these lineages. In this review, we elaborate on these diverse pathogenic mechanisms underlying cell plasticity and signaling reprogramming as well as discuss the related diagnostic and therapeutic implications and challenges.

Differentiating Between Epstein-Barr Virus-positive Lymphoid Neoplasm Relapse and Post-transplant Lymphoproliferative Disorder After Sex-mismatched Hematopoietic Stem Cell Transplantation

After allogeneic hematopoietic stem cell transplantation (HSCT), accurate differentiation between donor-derived post-transplant lymphoproliferative disorder (PTLD) and relapse of recipient-derived lymphoproliferative disorder (LPD) is crucial for determining treatment. Conventional diagnostic approaches for PTLD include histopathological examination, flow cytometry, and chimerism analysis of bulk tumor tissue. However, these methods are inconclusive in cases in which the primary disease is an Epstein-Barr virus (EBV)-positive LPD and is of the same lineage as that of the post-HSCT LPD tumor cells. Particularly, in cases where the number of tumor cells in the tissue is low, it is difficult to determine the origin of tumor cells. In this study, we developed a new method to simultaneously detect signals using sex chromosome fluorescence in situ hybridization, immunofluorescence staining, and EBV-encoded small RNA in situ hybridization on a single section of formalin-fixed paraffin-embedded histopathological specimen. The utility of the method was validated using specimens from 6 cases of EBV-positive LPD after sex-mismatched HSCT that were previously difficult to diagnose, including Hodgkin lymphoma-like PTLD that developed after HSCT for Hodgkin lymphoma and recurrence of chronic active EBV infection. This method successfully preserved the histologic structure after staining and allowed accurate determination of tumor cell origin and lineage at the single-cell level, providing a definitive diagnosis in all cases. This method provides a powerful tool for the diagnosis of LPDs after sex-mismatched HSCT.

Cutaneous Intravascular Hematolymphoid Entities: A Review

Intravascular lymphomas are rare disease conditions that exhibit neoplastic lymphoid cells that are confined mainly to the lumens of small capillaries and medium-sized vessels. The majority of the intravascular lymphomas are of B-cell origin, but they can include NK/T-cell and CD30+ immunophenotypes. In the histologic differential diagnosis are benign proliferations such as intralymphatic histiocytosis and intravascular atypical CD30+ T-cell proliferation. In this review, we discuss the clinical, histopathologic, and molecular findings of intravascular B-cell lymphoma, intravascular NK/T-cell lymphoma, intralymphatic histiocytosis, and benign atypical intravascular CD30+ T-cell proliferation.

Case Report: Post-transplant lymphoproliferative disorder as a serious complication of vascularized composite allotransplantation

Vascularized composite allotransplantation (VCA) is an emerging field in transplant surgery. Despite overall positive outcomes, VCA confers risk for multiple complications related to the procedure and subsequent immunosuppression. Post-transplant lymphoproliferative disorder (PTLD) is a heterogeneous group of lymphoproliferative disorders occurring after solid organ and hematopoietic stem cell transplant. A patient with PTLD after bilateral upper extremity transplantation is presented as well as a review of all known cases of PTLD after VCA, with a focus on the unique epidemiology, presentation, and treatment in this population.

Epstein-Barr virus latency patterns in polymorphic lymphoproliferative disorders and lymphomas in immunodeficiency settings: Diagnostic implications

Epstein-Barr virus (EBV) is responsible for many B cell lymphoproliferative disorders (LPD) spanning subclinical infection to immunodeficiency-related neoplasms. EBV establishes a latent infection in the host B cell as defined histologically by the expression of EBV latent membrane proteins and nuclear antigens. Herein, we characterize the latency patterns of immunodeficiency-related neoplasms including post-transplant lymphoproliferative disorders (PTLD) and therapy-related LPD (formerly iatrogenic) with latent membrane protein-1 (LMP-1) and EBV nuclear antigen-2 (EBNA-2) immunohistochemistry. The latency pattern was correlated with immunodeficiency and dysregulation (IDD) status and time from transplant procedure. 38 cases of EBV+ PTLD in comparison to 27 cases of classic Hodgkin lymphoma (CHL) and diffuse large B cell lymphoma (DLBCL) arising in either the therapy-related immunodeficiency setting (n = 12) or without an identified immunodeficiency (n = 15) were evaluated for EBV-encoded small RNAs by in situ hybridization (EBER-ISH) and for LMP-1 and EBNA-2 by immunohistochemistry. A full spectrum of EBV latency patterns was observed across PTLD in contrast to CHL and DLBCL arising in the therapy-related immunodeficiency setting. Polymorphic-PTLD (12 of 16 cases, 75 %) and DLBCL-PTLD (9 of 11 cases, 82 %) showed the greatest proportion of cases with latency III pattern. Whereas, EBV+ CHL in an immunocompetent patient showed exclusively latency II pattern (13 of 13 cases, 100 %). The majority of EBV+ PTLD occurred by three years of transplant procedure date and were enriched for latency III pattern (21 of 22 cases, 95 %). Immunohistochemical identification of EBV latency by LMP-1 and EBNA-2 can help classify PTLD in comparison to other EBV+ B cell LPD and lymphomas arising in therapy-related immunodeficiency and non-immunodeficiency settings.

Targeting latent viral infection in EBV-associated lymphomas

Epstein-Barr virus (EBV) contributes to the development of a significant subset of human lymphomas. As a herpes virus, EBV can transition between a lytic state which is required to establish infection and a latent state where a limited number of viral antigens are expressed which allows infected cells to escape immune surveillance. Three broad latency programs have been described which are defined by the expression of viral proteins RNA, with latency I being the most restrictive expressing only EBV nuclear antigen 1 (EBNA1) and EBV-encoded small RNAs (EBERs) and latency III expressing the full panel of latent viral genes including the latent membrane proteins 1 and 2 (LMP1/2), and EBNA 2, 3, and leader protein (LP) which induce a robust T-cell response. The therapeutic use of EBV-specific T-cells has advanced the treatment of EBV-associated lymphoma, however this approach is only effective against EBV-associated lymphomas that express the latency II or III program. Latency I tumors such as Burkitt lymphoma (BL) and a subset of diffuse large B-cell lymphomas (DLBCL) evade the host immune response to EBV and are resistant to EBV-specific T-cell therapies. Thus, strategies for inducing a switch from the latency I to the latency II or III program in EBV+ tumors are being investigated as mechanisms to sensitize tumors to T-cell mediated killing. Here, we review what is known about the establishment and regulation of latency in EBV infected B-cells, the role of EBV-specific T-cells in lymphoma, and strategies to convert latency I tumors to latency II/III.

Diagnostic and prognostic molecular pathology of lymphoid malignancies

With the explosion in knowledge about the molecular landscape of lymphoid malignancies and the increasing availability of high throughput techniques, molecular diagnostics in hematopathology has moved from isolated marker studies to a more comprehensive approach, integrating results of multiple genes analyzed with a variety of techniques on the DNA and RNA level. Although diagnosis of lymphoma still relies on the careful integration of clinical, morphological, phenotypic, and, if necessary molecular features, and only few entities are defined strictly by genetic features, genetic profiling has contributed profoundly to our current understanding of lymphomas and shaped the two current lymphoma classifications, the International Consensus Classification and the fifth edition of the WHO classification of lymphoid malignancies. In this review, the current state of the art of molecular diagnostics in lymphoproliferations is summarized, including clonality analysis, mutational studies, and gene expression profiling, with a focus on practical applications for diagnosis and prognostication. With consideration for differences in accessibility of high throughput techniques and cost limitations, we tried to distinguish between diagnostically relevant and in part disease-defining molecular features and optional, more extensive genetic profiling, which is usually restricted to clinical studies, patients with relapsed or refractory disease or specific therapeutic decisions. Although molecular diagnostics in lymphomas currently is primarily done for diagnosis and subclassification, prognostic stratification and predictive markers will gain importance in the near future.

Are corticosteroids safe in adolescent and adult patients with infectious mononucleosis? A retrospective cohort study

BACKGROUND AND AIM

The use of systemic corticosteroids during Epstein-Barr virus (EBV)-induced infectious mononucleosis is a controversial but widespread practice. We aimed to investigate the frequency of complications in adolescents and adults with infectious mononucleosis in relation to the use of corticosteroids.

METHODS

We reviewed the clinical records of 396 patients admitted to the hospital with infectious mononucleosis (52.0% male; median age, 19 years; range, 15-87 years), with a focus on both short-term (infectious and non-infectious) and long-term (hematological malignancies) complications in relation to corticosteroid use.

RESULTS

A total of 155 (38.6%) patients received corticosteroids at some point during infectious mononucleosis. Corticosteroid use was significantly (P≤0.002) associated with sore throat, lymphadenopathy, leukocytosis, and with antibiotics use (mainly indicated after suspicion of tonsillar bacterial superinfection). Overall, 139/155 (89.7%) patients who were treated with corticosteroids also received antibiotics either before or during hospitalization, compared with 168/241 (69.7%) patients who did not. The frequency of short-term severe complications, either infectious (peritonsillar-parapharyngeal abscess or bacteremia) or non-infectious (splenic rupture, severe thrombocytopenia, myopericarditis, or lymphocytic meningitis) were similar in patients receiving and not receiving corticosteroids. After a median of 15 years of follow-up, only one Hodgkin's lymphoma was diagnosed, in a patient who was not treated with corticosteroids during infectious mononucleosis.

CONCLUSIONS

The use of systemic corticosteroids during EBV-induced infectious mononucleosis is generally safe, at least with concomitant antibiotic therapy. However, this should not encourage the use of corticosteroids in this context, given that their efficacy has yet to be demonstrated.

Chronic active Epstein-Barr virus disease originates from infected hematopoietic stem cells

ABSTRACT

Chronic active Epstein-Barr virus (EBV) disease (CAEBV) is a lethal syndrome because of persistent EBV infection. When diagnosed as CAEBV, EBV infection was observed in multiple hematopoietic lineages, but the etiology of CAEBV is still elusive. Bone marrow and peripheral cells derived from 5 patients with CAEBV, 1 patient with EBV-associated hemophagocytic lymphohistiocytosis, and 2 healthy controls were analyzed. Multiple assays were applied to identify and characterize EBV-infected cells, including quantitative polymerase chain reaction, PrimeFlow, and single-cell RNA-sequencing (scRNA-seq). Based on scRNA-seq data, alterations in gene expression of particular cell types were analyzed between patients with CAEBV and controls, and between infected and uninfected cells. One patient with CAEBV was treated with allogeneic hematopoietic stem cell transplantation (HSCT), and the samples derived from this patient were analyzed again 6 months after HSCT. EBV infected the full spectrum of the hematopoietic system including both lymphoid and myeloid lineages, as well as the hematopoietic stem cells (HSCs) of the patients with CAEBV. EBV-infected HSCs exhibited a higher differentiation rate toward downstream lineages, and the EBV infection had an impact on both the innate and adaptive immunity, resulting in inflammatory symptoms. EBV-infected cells were thoroughly removed from the hematopoietic system after HSCT. Taken together, multiple lines of evidence presented in this study suggest that CAEBV disease originates from the infected HSCs, which might potentially lead to innovative therapy strategies for CAEBV.

Hydroa Vacciniforme Lymphoproliferative Disorder in a Young Spanish Woman: An Infrequent Case With Fatal Outcome

ABSTRACT

Hydroa vacciniforme (HV) lymphoproliferative disorder is a rare NK/T-cell lymphoma mainly affecting children and with a clinical resemblance to HV, which is mostly reported in Latin American and some Asian countries. Overall, the mature T cell and NK-cell neoplasms are now grouped into 9 families based on diverse concepts: cell of origin/differentiation state, clinical scenario, disease localization, and cytomorphology. HV lymphoproliferative disorder is listed within the group of Ebstein Barr Virus-positive T-cell and NK-cell lymphoid proliferations and lymphomas of childhood according to the fifth edition of the World Health Organization Classification of mature lymphoid neoplasms. We report the extraordinary case of a 22-year-old white woman, native of Spain, first presented in 2016 when she started suffering from recurrent facial edema. Four years later, the disease progressed with lymph node spreading and a fatal outcome. Here, we describe the clinical and histological presentation of the lymphoma throughout its evolution. Cases like this can be difficult to classify posing a real challenge to clinicians and pathologists. So, it is vital to be aware of the rare presentation of this disease to be able to identify the clinical and histological picture to make a correct diagnosis and establish an early treatment.

Updates in the Classification of T-cell Lymphomas and Lymphoproliferative Disorders

PURPOSE OF REVIEW

Mature T/NK-cell neoplasms comprise a heterogeneous group of diseases with diverse clinical, histopathologic, immunophenotypic, and molecular features. A clinically relevant, comprehensive, and reproducible classification system for T/NK-cell neoplasms is essential for optimal management, risk stratification, and advancing understanding of these diseases. Two classification systems for lymphoid neoplasms were recently introduced: the 5th edition of World Health Organization classification (WHO-HAEM5) and the 2022 International Consensus Classification (ICC). In this review, we summarize the basic framework and updates in the classification of mature T/NK-cell neoplasms.

RECENT FINDINGS

WHO-HAEM5 and ICC share basic concepts in classification of T/NK-cell neoplasms, emphasizing integration of clinical presentation, pathology, immunophenotype, and genetics. Major updates in both classifications include unifying nodal T-follicular helper-cell lymphomas into a single entity and establishing EBV-positive nodal T/NK-cell lymphoma as a distinct entity. However, some differences exist in taxonomy, terminology, and disease definitions. The recent classifications of mature T/NK-cell neoplasms are largely similar and provide new insights into taxonomy based on integrated clinicopathologic features.

What is new in the classification of peripheral T cell lymphomas?

In this review focus article, we highlight the main modifications introduced in the latest 2022 International Consensus Classification and World Health Organization classification (ICC and WHO-HAEM5) of mature T (and NK) cell neoplasms (PTCLs) and consequent implications for diagnostic practice. The changes result from recent advances in the genomic and molecular characterization of PTCLs and enhanced understanding of their pathobiology. Specifically, consideration is given to the following groups of diseases: Epstein-Barr virus (EBV)-associated neoplasms; follicular helper T cell lymphoma; anaplastic large cell lymphomas; primary intestinal T and NK cell lymphomas and lymphoproliferative disorders; and PTCL, not otherwise specified.

The 2022 classifications of lymphoid neoplasms : Keynote

Classification of hematological neoplasms in the past 25 years has been generated through international efforts to achieve broad consensus among professionals. In recent years, the understanding of lymphoid neoplasms has advanced notably, particularly with the impact of genomic studies. Two classifications of these neoplasms were produced in 2022. The International Consensus Classification (ICC) was generated following the same successful process used for the third, fourth, and updated fourth editions of the World Health Organization (WHO) Classification of Hematologic Neoplasms, coordinated by a steering committee approved by the Executive Committees of the European Association for Haematopathology and the Society of Hematopathology. The topics were prepared by different working groups and subsequently discussed in the clinical advisory committee (CAC) meeting with the participation of a large group of pathologists, clinicians, and scientists who all approved the classification after reaching consensus on all topics. Simultaneously, the International Agency for Cancer Research (IARC) of the WHO has produced the fifth edition of the classification of these neoplasms with a group of professionals appointed by the agency who discussed the proposed classification in different meetings. The definition and criteria for diagnosis of many entities have been refined in both proposals. Terminology for some diseases has been adapted to the current knowledge of their biology. Major findings from recent genomic studies have impacted the conceptual framework and diagnostic criteria for many entities. Although most categories are similar in both classifications, there are also conceptual differences and differences in the diagnostic criteria for some diseases.

A personalized approach to lymphoproliferations in patients with inborn errors of immunity

Biopsies from patients with inborn error of immunity (IEI) may pose a diagnostic challenge due to the abnormal anatomy of their lymphoid organs and the tendency for the development of lymphoproliferations in various organs, some of which may lead to the wrong impression of malignant lymphoma which may prompt aggressive unnecessary treatment. In this article we will review typical histologic findings in various IEI's described in the literature and discuss the appropriate approach to the diagnosis of lymphoproliferations in these patients by presenting illustrative cases.

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.

Liver Pathology After Hematopoietic Stem Cell Transplantation

Hematopoietic stem cell transplantation is used to treat a variety of hematologic malignancies and autoimmune conditions. The immunosuppressive medications as well as other therapies used both before and after transplantation leave patients susceptible to a wide spectrum of complications, including liver injury. Causes for liver damage associated with stem cell transplantation include sinusoidal obstruction syndrome, graft-versus-host disease, iron overload, and opportunistic infection. Here, the authors review the clinical and pathological findings of these etiologies of liver injury and provide a framework for diagnosis.

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.

Post-transplant Lymphoproliferative Disorder (PTLD) in the US Population: Demographics, Treatment Characteristics, and Survival Analysis

BACKGROUND

Post-transplant lymphoproliferative disorder (PTLD) is a lymphoplasmacytic proliferative disorder in the setting of hematopoietic stem cells and solid organ transplants. PTLD is divided into nondestructive, polymorphic, monomorphic, and classical Hodgkin lymphoma subtypes. Most cases of PTLDs are Epstein-Barr virus (EBV) related (two third of the cases), and most are of B cell (80-85%) origin. The polymorphic PTLD subtype can be locally destructive and show malignant features. Treatment for PTLD includes a reduction in immunosuppression, surgery, cytotoxic chemotherapy and/or immunotherapy, anti-viral agents, and/or radiation. The aim of this study was to examine the demographic factors and treatment modalities that influence survival in patients with polymorphic PTLD.

METHODS

About 332 cases of polymorphic PTLD were identified from 2000 to 2018 using the Surveillance, Epidemiology, and End Results (SEER) database.

RESULTS

The median age of the patients was found to be 44 years. The most common age groups were between the ages of 1-19 years (n=100. 30.1%) and 60-69 years (n=70. 21.1%). The majority of cases in this cohort underwent systemic (cytotoxic chemo and/or immuno) therapy only (n=137, 41.3%), while 129 (38.9%) cases did not undergo any treatment. The overall five-year observed survival was 54.6% (95% confidence interval (CI), 51.1 - 58.1). One-year and five-year survival with systemic therapy was 63.8% (95% CI, 59.6 - 68.0) and 52.5% (95% CI, 47.7 - 57.3), respectively. The one-year and five-year survival with surgery was 87.3% (95% CI, 81.2-93.4) and 60.8% (95% CI., 42.2 - 79.4), respectively. The one-year and five-year without therapy were 67.6% (95% CI, 63.2-72.0) and 49.6% (95% CI, 43.5-55.7), respectively. Univariate analysis revealed that surgery alone (hazard ratio (HR) 0.386 (0.170-0.879), p = 0.023) was a positive predictor of survival. Race and sex were not predictors of survival, although age >55 years was a negative predictor for survival (HR 1.128 (1.139-1.346), p <0.001).

CONCLUSION

Polymorphic PTLD is a destructive complication of organ transplantation that is usually associated with EBV positivity. We found that it most often presents in the pediatric age group, and its occurrence in those older than 55 years was associated with a worse prognosis. Treatment with surgery alone is associated with improved outcomes and should be considered in addition to a reduction in immunosuppression in cases of polymorphic PTLD.

[Classification of peripheral T-cell lymphomas : News and open questions]

Recently, two new classifications were released: the International Consensus Classification (ICC) drafted by the Clinical Advisory Committee and the short version of the 5th Edition of the WHO classification of hematolymphoid tumors. In light of new clinical, morphological, and molecular data, both classifications also revised the classification of peripheral T‑cell lymphomas. In addition to relatively minor changes in terminology and disease definitions, both new classifications mirror the considerable gain of knowledge on the genetic alterations of different T‑cell lymphoma entities. The present review summarizes the most important changes for T‑cell lymphomas in both classifications, the differences between the classifications, and diagnostically relevant issues.

Who is the patient at risk for EBV reactivation and disease: expert opinion focused on post-transplant lymphoproliferative disorders following hematopoietic stem cell transplantation

INTRODUCTION

Post-transplant lymphoproliferative disorders (PTLD) represent a diverse group of diseases. They develop as a consequence of uncontrolled proliferation of lymphoid or plasmacytic cells resulting from T-cell immunosuppression after transplantation of either hematopoietic cells (HCT) or solid organs (SOT), caused mainly by latent Epstein-Barr virus (EBV). The risk for EBV recurrence is dependent on the level of incompetency of the immune system, presented as an impairment of T-cell immunity.

AREAS COVERED

This review summarizes the data on incidence and risk factors of EBV infection in patients after HCT. The median rate of EBV infection in HCT recipients was estimated at 30% after allogeneic and<1% after autologous transplant; 5% in non-transplant hematological malignancies; 30% in SOT recipients. The median rate of PTLD after HCT is estimated at 3%. The most frequently reported risk factors for EBV infection and disease include: donor EBV-seropositivity, use of T-cell depletion, especially with ATG; reduced-intensity conditioning; mismatched family or unrelated donor transplants; and acute or chronic graft-versus-host-disease.

EXPERT OPINION

The major risk factors for EBV infection and EBV-PTLD can be easily identified: EBV-seropositive donor, depletion of T-cells, and the use of immunosuppressive therapy. Strategies for avoiding risk factors include elimination EBV from the graft and improving T-cell function.

A young woman with persistent sore throat, Epstein-Barr virus, lymphadenopathy, and aberrant CD4 + CD7- T-cells

A young woman with persistent EBV viremia and lymphocytosis had an abnormal CD4- T cell population with aberrant loss of CD7. She had a diagnosis of chronic active EBV (CAEBV), a lymphoproliferative disorder for which she ultimately required allogeneic hematopoietic stem cell transplantation.

Case report: Immune modulation after PD-1 inhibitor therapy in a patient with extranodal NK/T-cell lymphoma secondary to chronic active Epstein-Barr virus disease unveiled by single-cell transcriptomics

Chronic active Epstein-Barr virus disease (CAEBV) is a systemic lymphoproliferative disorder that is closely linked to Epstein-Barr virus (EBV) infection. The clinical course and severity of CAEBV can vary, and in some cases, it can progress to overt lymphoma, which is characterized by extranodal natural killer/T-cell lymphoma (ENKTL) and has a poor clinical outcome. Although anti-programmed cell death protein-1 (PD-1) therapy has shown effectiveness in some patients with EBV-associated disease, it has been less successful in others, and the exact mechanism of action of PD-1 inhibitor therapy in these diseases remains unclear. In this report, we describe a patient who was diagnosed with ENKTL secondary to CAEBV and experienced rapid disease progression accompanied by hyperinflammation after receiving PD-1 inhibitor therapy. Single-cell RNA sequencing revealed a significant increase in the patient's lymphocyte count, especially in natural killer cells, with increased activity following PD-1 inhibitor therapy. This case raises questions about the efficacy and safety of PD-1 inhibitor therapy in patients with EBV-associated diseases.

Evolution in the definition and diagnosis of the Hodgkin lymphomas and related entities

Hodgkin lymphoma was the first of the lymphomas to be recognized as a specific disease entity. However, recent studies have highlighted the heterogeneity of the diseases associated with this eponym warranting clarification and refinement of diagnostic terminology. While classic Hodgkin lymphoma (CHL) remains an essentially unchanged diagnostic entity in the 2022 International Consensus Classification of Mature Lymphoid Neoplasms (2022 ICC), nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) is now renamed nodular lymphocyte predominant B cell lymphoma (NLPBL) in recognition of the distinct pathologic, biologic, and clinical differences. Fan patterns A, B, and C (sharing the presence of evident follicular structures, and retention of a B cell rich background) will be combined in "typical" or grade 1, while the other "variant" patterns, D, E, and F, are considered grade 2. T-cell/histiocyte-rich large B cell lymphoma (THRBCL) is considered part of the "variant" NLPHL continuum.The entity previously known as "B cell lymphoma, unclassifiable (BCLU), with features intermediate between diffuse large B cell lymphoma (DLBCL) and CHL" has been renamed "mediastinal gray zone lymphoma" (MGZL) in recognition of the importance of the thymic niche in the biology of this tumor. The diagnostic criteria for MGZL have been refined and require both a high tumor cell density and a strongly preserved B cell program.This article will describe updates on CHL, NLPBL, and MGZL in the recently published 2022 ICC and provide some useful differential diagnostic clues in cases with atypical morphology or immunophenotype.

Intravascular NK/T-Cell Lymphoma: What We Know about This Diagnostically Challenging, Aggressive Disease

Intravascular lymphoma is a form of lymphoid malignancy characterized by neoplastic cells growing almost exclusively within the lumina of small- to medium-sized blood vessels. Most cases are of B-cell origin with rare cases of natural killer or T-cell lineage. Extranodal sites are affected, mainly the skin and central nervous system, although any organ may be involved. Intravascular NK/T-cell lymphoma deserves special attention because of its clinicopathologic features and the need for adequate immunophenotyping combined with clonality test for a proper diagnosis. Moreover, intravascular NK/T-cell lymphoma is strongly linked to Epstein-Barr virus (EBV), which is considered to play a role in tumorigenesis and to be responsible for the aggressive behavior of the disease. In this paper, we review the current knowledge on this rare lymphoma and, in particular, the most recent advances about its molecular landscape. The main distinguishing features with other EBV-related entities, such as extranodal NK/T-cell lymphoma, EBV-positive primary nodal T/NK-cell lymphoma, and aggressive NK-cell leukemia, are discussed to help pathologists obtain the correct diagnosis and consequently develop an adequate and prompt therapy response.