Genetic landscape of T- and NK-cell post-transplant lymphoproliferative disorders

EBV-Related Lymphoproliferative Diseases: A Review in Light of New Classifications

Epstein-Barr virus (EBV) is a prevalent virus that can be detected in the vast majority of the population. Most people are asymptomatic and remain chronically infected throughout their lifetimes. However, in some populations, EBV has been linked to a variety of B-cell lymphoproliferative disorders (LPDs), such as Burkitt lymphoma, classic Hodgkin lymphoma, and other LPDs. T-cell LPDs have been linked to EBV in part of peripheral T-cell lymphomas, angioimmunoblastic T-cell lymphomas, extranodal nasal natural killer/T-cell lymphomas, and other uncommon histotypes. This article summarizes the current evidence for EBV-associated LPDs in light of the upcoming World Health Organization classification and the 2022 ICC classification.

How I treat posttransplant lymphoproliferative disorder

Posttransplant lymphoproliferative disorder (PTLD) is an important and potentially life-threatening complication of solid organ transplant and hematopoietic stem cell transplant (HSCT). Given the heterogeneity of PTLD and the risk of infectious complications in patients with immunosuppression, the treatment of this disease remains challenging. Monomorphic PTLD and lymphoma of B-cell origin account for the majority of cases. Treatment strategies for PTLD consist of response-adapted, risk-stratified methods using immunosuppression reduction, immunotherapy, and/or chemotherapy. With this approach, ∼25% of the patients do not need chemotherapy. Outcomes for patients with high risk or those who do not respond to frontline therapies remain dismal, and novel treatments are needed in this setting. PTLD is associated with Epstein-Barr virus (EBV) infection in 60% to 80% of cases, making EBV-directed therapy an attractive treatment modality. Recently, the introduction of adoptive immunotherapies has become a promising option for refractory cases; hopefully, these treatment strategies can be used as earlier lines of therapy in the future.

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

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

Important Considerations in the Diagnosis and Management of Post-transplant Lymphoproliferative Disorder

PURPOSE OF REVIEW

A relative lack of molecular and clinical studies compared to other lymphoid cancers has historically made it difficult to determine optimal management approaches in post-transplant lymphoproliferative disorder (PTLD). We sought to better define the "state of the science" in PTLD by examining recent advances in risk assessment, genomic profiling, and trials of PTLD-directed therapy.

RECENT FINDINGS

Several major clinical trials highlight risk-stratified sequential therapy incorporating rituximab with or without chemotherapy as a rational treatment strategy in patients with CD20+ PTLD who do not respond to reduction of immunosuppression alone. Epstein Barr virus (EBV)-targeted cytotoxic lymphocytes are a promising approach in patients with relapsed/refractory EBV+ PTLD, but dedicated clinical trials should determine how autologous chimeric antigen receptor T cell therapy (CAR-T) may be safely administered to PTLD patients. Sequencing studies underscore the important effect of EBV infection on PTLD pathogenesis, but comprehensive genomic and tumor microenvironment profiling are needed to identify biomarkers that predict response to treatment in this clinically heterogeneous disease.

SWI/SNF complexes in hematological malignancies: biological implications and therapeutic opportunities

Hematological malignancies are a highly heterogeneous group of diseases with varied molecular and phenotypical characteristics. SWI/SNF (SWItch/Sucrose Non-Fermentable) chromatin remodeling complexes play significant roles in the regulation of gene expression, being essential for processes such as cell maintenance and differentiation in hematopoietic stem cells. Furthermore, alterations in SWI/SNF complex subunits, especially in ARID1A/1B/2, SMARCA2/4, and BCL7A, are highly recurrent across a wide variety of lymphoid and myeloid malignancies. Most genetic alterations cause a loss of function of the subunit, suggesting a tumor suppressor role. However, SWI/SNF subunits can also be required for tumor maintenance or even play an oncogenic role in certain disease contexts. The recurrent alterations of SWI/SNF subunits highlight not only the biological relevance of SWI/SNF complexes in hematological malignancies but also their clinical potential. In particular, increasing evidence has shown that mutations in SWI/SNF complex subunits confer resistance to several antineoplastic agents routinely used for the treatment of hematological malignancies. Furthermore, mutations in SWI/SNF subunits often create synthetic lethality relationships with other SWI/SNF or non-SWI/SNF proteins that could be exploited therapeutically. In conclusion, SWI/SNF complexes are recurrently altered in hematological malignancies and some SWI/SNF subunits may be essential for tumor maintenance. These alterations, as well as their synthetic lethal relationships with SWI/SNF and non-SWI/SNF proteins, may be pharmacologically exploited for the treatment of diverse hematological cancers.

PTCL, NOS: An update on classification, risk-stratification, and treatment

The peripheral T-cell lymphomas (PTCL) are relatively rare, heterogeneous, and therapeutically challenging. While significant therapeutic gains and improved understanding of disease pathogenesis have been realized for selected PTCL subtypes, the most common PTCL in North America remains "not otherwise specified (NOS)" and is an unmet need. However, improved understanding of the genetic landscape and ontogeny for the PTCL subtypes currently classified as PTCL, NOS have been realized, and have significant therapeutic implications, which will be reviewed here.

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

EBV-associated lymphoproliferative disorders (LPD) include conditions of B, T, and NK cell derivation with a wide clinicopathological spectrum ranging from indolent, self-limiting, and localized conditions to highly aggressive lymphomas. Since the 2016 World Health Organization (WHO) lymphoma classification, progress has been made in understanding the biology of the EBV-associated LPDs. The diagnostic criteria of EBV+ mucocutaneous ulcer and lymphomatoid granulomatosis have been refined, and a new category of EBV-positive polymorphic B cell LPD was introduced to encompass the full spectrum of EBV-driven B cell disorders. The differential diagnosis of these conditions is challenging. This report will present criteria to assist the pathologist in diagnosis. Within the group of EBV-associated T and NK cell lymphomas, a new provisional entity is recognized, namely, primary nodal EBV+ T or NK cell lymphoma. The EBV + T and NK cell LPDs in children have undergone major revisions. In contrast to the 2016 WHO classification, now four major distinct groups are recognized: hydroa vacciniforme (HV) LPD, severe mosquito bite allergy, chronic active EBV (CAEBV) disease, and systemic EBV-positive T cell lymphoma of childhood. Two forms of HV LPD are recognized: the classic and the systemic forms with different epidemiology, clinical presentation, and prognosis. The subclassification of PTLD, not all of which are EBV-positive, remains unaltered from the 2016 WHO classification. This review article summarizes the conclusions and the recommendations of the Clinical Advisory Committee (CAC), which are summarized in the International Consensus Classification of Mature Lymphoid Neoplasms.

Primary pulmonary T-cell lymphoproliferative disorders with a limited-stage, low proliferative index, and unusual clinical behavior: two cases of a rare occurrence

Extranodal T-lymphoproliferative disorders or T-cell lymphomas (TLPD) are classified according to the WHO Classification (4th and upcoming 5th editions) (Swerdlow et al., IARC Press 1; Alaggio et al., Leukemia 36(7):1720-1748, 2) and to the International Consensus Classification Update (Campo et al., Blood 140(11):1229-1253, 3) upon several morphologic, phenotypic, and genetic features. None of those at present included has been characterized by primary pulmonary onset. We herein present two such cases which, to the best of our knowledge, have not been previously reported and that might represent another variant of T-cell proliferation at mucosal sites. The two cases share similar histological and phenotypic features, suggesting an origin from CD4 + effector memory T cells with the expression of a CD279/PD-1 antigen. They are both monoclonal, harbor few mutations, and show no disease progression outside the lung. They only differ concerning the local extension of the process and clinical setting. The two cases are examples of so far unreported primary pulmonary TLDP, with limited stage and low proliferative index. A possible relationship with a local yet unknown inflammatory trigger that might have favored the development of the T-cell clone cannot be ruled out.

Advances in the understanding and treatment of Cutaneous T-cell Lymphoma

Cutaneous T-cell lymphomas (CTCL) are a heterogeneous group of non-Hodgkin's lymphomas (NHL) characterised by the clonal proliferation of malignant, skin homing T-cells. Recent advances have been made in understanding the molecular pathogenesis of CTCL. Multiple deep sequencing studies have revealed a complex genomic landscape with large numbers of novel single nucleotide variants (SNVs) and copy number variations (CNVs). Commonly perturbed genes include those involved in T-cell receptor signalling, T-cell proliferation, differentiation and survival, epigenetic regulators as well as genes involved in genome maintenance and DNA repair. In addition, studies in CTCL have identified a dominant UV mutational signature in contrast to systemic T-cell lymphomas and this likely contributes to the high tumour mutational burden. As current treatment options for advanced stages of CTCL are associated with short-lived responses, targeting these deregulated pathways could provide novel therapeutic approaches for patients. In this review article we summarise the key pathways disrupted in CTCL and discuss the potential therapeutic implications of these findings.

A Rare Case of Monomorphic T-Cell Posttransplant Lymphoproliferative Disorder Presenting as Primary Cutaneous Anaplastic Large Cell Lymphoma, ALK Negative

ABSTRACT

Posttransplant lymphoproliferative disorders are a serious complication of hematopoietic and solid organ transplants secondary to iatrogenic immunosuppression. Most cases present as B-cell proliferations which are often Epstein-Barr virus positive; however, ∼10% of cases are T/NK cell and are less commonly associated with Epstein-Barr virus. Of these, cutaneous T/NK-cell lymphomas are exceedingly rare. We report a case of a 69-year-old male, liver transplant recipient who presented with a tender, bright red papule on the left arm during his annual skin cancer screening. Histopathologic evaluation revealed pleomorphic cells with enlarged nuclei, vesicular chromatin, and frequent mitotic figures, intercalating through the dermis. The tumor formed single strands and small cords without epidermal involvement. A patchy mild mixed inflammatory infiltrate was associated with the tumor. Tumor cells were CD2(+), CD4(+), CD30(+), CD3(-), CD20(-), ALK-1(-), and EBER(-). Molecular studies revealed a monoclonal T-cell receptor gamma gene rearrangement by polymerase chain reaction (PCR); ALK gene rearrangement was negative by fluorescence in situ hybridization (FISH). Taken together, the findings were consistent with an ALK-negative anaplastic large cell lymphoma involving skin, which, given the history of liver transplant, qualified as a monomorphic T-cell posttransplant lymphoproliferative disorder. Follow-up imaging studies showed no evidence of systemic disease, supporting an interpretation of primary cutaneous anaplastic large cell lymphoma.

Post-transplant Lymphoproliferative Disorder Following Cardiac Transplantation

Post-transplant lymphoproliferative disorder (PTLD) is a spectrum of lymphoid conditions frequently associated with the Epstein Barr Virus (EBV) and the use of potent immunosuppressive drugs after solid organ transplantation. PTLD remains a major cause of long-term morbidity and mortality following heart transplantation (HT). Epstein-Barr virus (EBV) is a key pathogenic driver in many PTLD cases. In the majority of PTLD cases, the proliferating immune cell is the B-cell, and the impaired T-cell immune surveillance against infected B cells in immunosuppressed transplant patients plays a key role in the pathogenesis of EBV-positive PTLD. Preventive screening strategies have been attempted for PTLD including limiting patient exposure to aggressive immunosuppressive regimens by tailoring or minimizing immunosuppression while preserving graft function, anti-viral prophylaxis, routine EBV monitoring, and avoidance of EBV seromismatch. Our group has also demonstrated that conversion from calcineurin inhibitor to the mammalian target of rapamycin (mTOR) inhibitor, sirolimus, as a primary immunosuppression was associated with a decreased risk of PTLD following HT. The main therapeutic measures consist of immunosuppression reduction, treatment with rituximab and use of immunochemotherapy regimens. The purpose of this article is to review the potential mechanisms underlying PTLD pathogenesis, discuss recent advances, and review potential therapeutic targets to decrease the burden of PTLD after HT.

Durable Response to Brentuximab Vedotin Plus Cyclophosphamide, Doxorubicin, and Prednisone (BV-CHP) in a Patient with CD30-Positive PTCL Arising as a Post-Transplant Lymphoproliferative Disorder (PTLD)

T-cell PTLDs are lymphoid proliferations that develop in recipients of SOT or allogeneic HSCT. They carry an extremely poor prognosis with a reported median survival of only 6 months. The infrequency with which they are encountered makes treatment a challenge due to the lack of prospective trials to guide management. The significantly higher risk of morbidity and mortality in T-cell PTLD, compared to B-cell PTLD, underscores the challenge of treating these patients and the need for new therapeutic options. Brentuximab vedotin, an ADC targeting CD30, is FDA-approved in combination with CHP as front-line treatment for patients with CD30 expressing PTCL. Herein we report a case of CD30-positive T-cell PTLD that was successfully treated with BV-CHP, suggesting the added value of the addition of BV to chemotherapy, contributing to our patient’s long and ongoing progression-free survival. To our knowledge, this is the first documented case of successful treatment using BV-CHP for a CD30-positive, EBV-negative, late T-cell PTLD.

Janus Kinase Signaling: Oncogenic Criminal of Lymphoid Cancers

Simple Summary

Janus kinases (JAKs) are transmembrane receptors that pass signals from extracellular ligands to downstream. Increasing evidence has suggested that JAK family aberrations promote lymphoid cancer pathogenesis and progression through mediating gene expression via the JAK/STAT pathway or noncanonical JAK signaling. We are here to review how canonical JAK/STAT and noncanonical JAK signalings are represented and deregulated in lymphoid malignancies and how to target JAK for therapeutic purposes.

Abstract

The Janus kinase (JAK) family are known to respond to extracellular cytokine stimuli and to phosphorylate and activate signal transducers and activators of transcription (STAT), thereby modulating gene expression profiles. Recent studies have highlighted JAK abnormality in inducing over-activation of the JAK/STAT pathway, and that the cytoplasmic JAK tyrosine kinases may also have a nuclear role. A couple of anti-JAK therapeutics have been developed, which effectively harness lymphoid cancer cells. Here we discuss mutations and fusions leading to JAK deregulations, how upstream nodes drive JAK expression, how classical JAK/STAT pathways are represented in lymphoid malignancies and the noncanonical and nuclear role of JAKs. We also summarize JAK inhibition therapeutics applied alone or synergized with other drugs in treating lymphoid malignancies.

Post-transplantation lymphoproliferative disorder after haematopoietic stem cell transplantation

Post-transplantation lymphoproliferative disorder (PTLD) is a severe complication of haematopoietic stem cell transplantation (HSCT), occurring in a setting of immune suppression and dysregulation. The disease is in most cases driven by the reactivation of the Epstein-Barr virus (EBV), which induces B cell proliferation through different pathomechanisms. Beyond EBV, many factors, variably dependent on HSCT-related immunosuppression, contribute to the disease development. PTLDs share several features with primary lymphomas, though clinical manifestations may be different, frequently depending on extranodal involvement. According to the WHO classification, histologic examination is required for diagnosis, allowing also to distinguish among PTLD subtypes. However, in cases of severe and abrupt presentation, a diagnosis based on a combination of imaging studies and EBV-load determination is accepted. Therapies include prophylactic and pre-emptive interventions, aimed at eradicating EBV proliferation before symptoms onset, and targeted treatments. Among them, rituximab has emerged as first-line option, possibly combined with a reduction of immunosuppression, while EBV-specific cytotoxic T lymphocytes are effective and safe alternatives. Though prognosis remains poor, survival has markedly improved following the adoption of the aforementioned treatments. The validation of innovative, combined approaches is the future challenge.

Immunophenotypic Spectrum and Genomic Landscape of Refractory Celiac Disease Type II

Refractory celiac disease type II (RCD II), also referred to as "cryptic" enteropathy-associated T-cell lymphoma (EATL) or "intraepithelial T-cell lymphoma," is a rare clonal lymphoproliferative disorder that arises from innate intraepithelial lymphocytes. RCD II has a poor prognosis and frequently evolves to EATL. The pathogenesis of RCD II is not well understood and data regarding the immunophenotypic spectrum of this disease and underlying genetic alterations are limited. To gain further biological insights, we performed comprehensive immunophenotypic, targeted next-generation sequencing, and chromosome microarray analyses of 11 RCD II cases: CD4-/CD8- (n=6), CD8+ (n=4), and CD4+ (n=1), and 2 of 3 ensuing EATLs. Genetic alterations were identified in 9/11 (82%) of the RCD II cases. All 9 displayed mutations in members of the JAK-STAT signaling pathway, including frequent, recurrent STAT3 (7/9, 78%) and JAK1 (4/9, 44%) mutations, and 9/10 evaluable cases expressed phospho-STAT3. The mutated cases also harbored recurrent alterations in epigenetic regulators (TET2, n=5 and KMT2D, n=5), nuclear factor-κB (TNFAIP3, n=4), DNA damage repair (POT1, n=3), and immune evasion (CD58, n=2) pathway genes. The CD4-/CD8- and other immunophenotypic subtypes of RCD II exhibited similar molecular features. Longitudinal genetic analyses of 4 RCD II cases revealed stable mutation profiles, however, additional mutations were detected in the EATLs, which occurred at extraintestinal sites and were clonally related to antecedent RCD II. Chromosome microarray analysis demonstrated copy number changes in 3/6 RCD II cases, and 1 transformed EATL with sufficient neoplastic burden for informative analysis. Our findings provide novel information about the immunophenotypic and genomic characteristics of RCD II, elucidate early genetic events in EATL pathogenesis, and reveal potential therapeutic targets.

Immunodeficiency-Related Lymphoid Proliferations: New Insights With Relevance to Practice

PURPOSE OF REVIEW

Our understanding of risk factors and mechanisms underlying immunosuppression-related lymphoproliferative disorders continues to evolve. An increasing number of patients are living with altered immune status due to HIV, solid organ or hematopoietic stem cell transplant, treatment of autoimmune disease, or advanced age. This review covers advances in understanding, emerging trends, and revisions to diagnostic guidelines.

RECENT FINDINGS

The tumor microenvironment, including interactions between the host immune system and tumor cells, is of increasing interest in the setting of immunosuppression. While some forms of lymphoproliferative disease are associated with unique risk factors, common mechanisms are also emerging. Indolent forms, such as Epstein-Barr virus positive mucocutaneous ulcer, are important to recognize. As methods to modulate the immune system evolve, more data are needed to understand and minimize lymphoproliferative disease risk. A better understanding of individual risk factors and common mechanisms underlying immunosuppression-related lymphoproliferations will ultimately enable improved prevention and treatment of these disorders.

High-throughput Sequencing of Subcutaneous Panniculitis-like T-Cell Lymphoma Reveals Candidate Pathogenic Mutations

Subcutaneous panniculitis-like T-cell lymphoma (SPTCL) is a malignant primary cutaneous T-cell lymphoma that is challenging to distinguish from other neoplastic and reactive panniculitides. In an attempt to identify somatic variants in SPTCL that may be diagnostically or therapeutically relevant, we performed both exome sequencing on paired tumor-normal samples and targeted sequencing of hematolymphoid-malignancy-associated genes on tumor biopsies. Exome sequencing was performed on skin biopsies from 4 cases of skin-limited SPTCL, 1 case of peripheral T-cell lymphoma, not otherwise specified with secondary involvement of the panniculus, and 2 cases of lupus panniculitis. This approach detected between 1 and 13 high-confidence somatic variants that were predicted to result in a protein alteration per case. Variants of interest identified include 1 missense mutation in ARID1B in 1 case of SPTCL. To detect variants that were present at a lower level, we used a more sensitive targeted panel to sequence 41 hematolymphoid-malignancy-associated genes. The targeted panel was applied to 2 of the biopsies that were evaluated by whole exome sequencing as well as 5 additional biopsies. Potentially pathogenic variants were identified in KMT2D and PLCG1 among others, but no gene was altered in >2 of the 7 cases sequenced. One variant that was notably absent from the cases sequences is RHOA G17V. Further work will be required to further elucidate the genetic abnormalities that lead to this rare lymphoma.

Hydroa vacciniforme-like lymphoproliferative disorder: A study of clinicopathology and whole-exome sequencing in Chinese patients

BACKGROUND

Hydroa vacciniforme-like lymphoproliferative disorder (HVLPD) encompasses a rare group of Epstein-Barr virus (EBV)-associated lymphoproliferative diseases.

OBJECTIVE

To define the clinical and pathologic characteristics of HVLPD and to identify mutant genes that may be related to the development of HVLPD.

METHODS

Clinical data and archived formalin-fixed, paraffin-embedded tissue were obtained from 19 patients. Specimens were analyzed by immunohistochemistry and in situ hybridization to detect EBV-encoded RNA (EBER1/2) and for T cell receptor (TCR) gene rearrangements. Whole-exome sequencing (WES) analysis was also performed in this study.

RESULTS

Thirteen patients survived between 3-58 months (median, 21 months) during the follow-up. Six patients who were almost adults (>15 years old) and died of the disease presented with facial edema. Lactate dehydrogenase (LDH) levels were elevated, and the TCR gene rearrangement test was positive more frequently in the patients who died. Compared with Chinese patients in a similar previous report, our patients had significantly higher proliferation (in all cases, the Ki-67 index was greater than 10 %) and a more aggressive clinical course. Moreover, after WES and Sanger verification, STAT3, IKBKB, ELF3, CHD7, KMT2D, ELK1, RARB and HPGDS were screened out in our patients.

CONCLUSIONS

HVLPD refers to a heterogeneous group of cutaneous lymphoproliferative diseases with different clinical and pathological features that affect patient outcomes. Gene mutations may be correlated with the development of HVLPD, and our study may provide new therapeutic targets for HVLPD.

Post-transplant indolent T cell lymphoproliferative disorder in living donor liver transplantation: a case report

Background

Post-transplant lymphoproliferative disorder (PTLD) of T cell type has been rarely reported. Accurate diagnosis of this life-threatening rare form of PTLD is important for the treatment strategy.

Case presentation

A 7-year-old boy had severe diarrhea and weight loss progressively at 7 years post-living donor liver transplantation (LDLT) for biliary atresia. Endoscopy in the gastrointestinal (GI) tract revealed multiple erosions and ulcer lesions with prominent intraepithelial lymphocytosis in the duodenum and terminal ileum. Immunohistochemical examination demonstrated that these accumulated lymphocytes mainly comprised small- to medium-sized T cells expressing CD3, CD4, CD5, CD7, and CD103, but lacking CD8, CD56, and Epstein-Barr virus-encoded small RNAs. In addition, T cell receptor β gene rearrangement was detected by polymerase chain reaction analysis. Comprehensively, the lesions were best interpreted as post-transplant indolent T cell lymphoproliferative disorder (LPD) of the intestine. Clinical remission was achieved by reducing the immunosuppressant.

Conclusion

A rarely reported indolent type of T cell LPD in post-LDLT was diagnosed by direct inspection and histological investigation. Although the histological classification and therapeutic strategy for post-transplant indolent T cell LPD have not been established, reducing immunosuppression allowed complete remission in our case. To prevent the incidence of PTLD and de novo malignancy, developing a methodology to set a proper dose of immunosuppressant is required.

Post-transplantation lymphoproliferative disorders: Current concepts and future therapeutic approaches

Transplant recipients are vulnerable to a higher risk of malignancy after solid organ transplantation and allogeneic hematopoietic stem-cell transplant. Post-transplant lymphoproliferative disorders (PTLD) include a wide spectrum of diseases ranging from benign proliferation of lymphoid tissues to frank malignancy with aggressive behavior. Two main risk factors of PTLD are: Firstly, the cumulative immunosuppressive burden, and secondly, the oncogenic impact of the Epstein-Barr virus. The latter is a key pathognomonic driver of PTLD evolution. Over the last two decades, a considerable progress has been made in diagnosis and therapy of PTLD. The treatment of PTLD includes reduction of immunosuppression, rituximab therapy, either isolated or in combination with other chemotherapeutic agents, adoptive therapy, surgical intervention, antiviral therapy and radiotherapy. In this review we shall discuss the prevalence, clinical clues, prophylactic measures as well as the current and future therapeutic strategies of this devastating disorder.

Refractory celiac disease type II: An atypical case highlighting limitations of the current classification system

Refractory celiac disease (RCD) is a rare condition associated with high morbidity that develops in individuals with celiac disease. It is known to be biologically heterogeneous, and currently two types are recognized based on immunophenotypic and molecular features, type I (RCD I) and type II (RCD II). Differentiating between RCD I and RCD II is critical, as patients with RCD II have substantially worse outcomes and a high risk of developing enteropathy-associated T-cell lymphoma. However, the current RCD classification is limited in scope, and atypical presentations and immunophenotypes are not recognized at present. Herein, we describe a unique case of RCD II with atypical clinical (primarily neurologic manifestations and lack of significant gastrointestinal symptoms), histopathologic (no villous atrophy), immunophenotypic (virtual absence of cytoplasmic CD3 expression), and molecular features (absence of clonal TR rearrangement and identification of pathogenic STAT3 and KMT2D mutations). This case highlights limitations of the current RCD classification system and the utility of next generation sequencing (NGS) studies in the diagnostic workup of RCD. Future algorithms need to recognize extraintestinal manifestations and incorporate atypical histopathologic and immunophenotypic features, as well as results of NGS analysis for RCD II classification.

Oral 5-azacytidine and romidepsin exhibit marked activity in patients with PTCL: a multicenter phase 1 study

The peripheral T-cell lymphomas (PTCLs) are uniquely sensitive to epigenetic modifiers. Based on the synergism between histone deacetylase inhibitors and hypomethylating agents that we established in preclinical PTCL models, we conducted a phase 1 study of oral 5-azacytidine (AZA) and romidepsin (ROMI) in patients with advanced lymphoid malignancies, with emphasis on PTCL. According to a 3 + 3 design, patients were assigned to 1 of 7 cohorts with AZA doses ranging from 100 mg daily on days 1 to 14 to 300 mg daily on days 1 to 21, ROMI doses ranging from 10 mg/m2 on days 8 and 15 to 14 mg/m2 on days 8, 15, and 22, with cycles of 21 to 35 days. Coprimary end points included maximum tolerated dose (MTD) and dose-limiting toxicity (DLT). We treated a total of 31 patients. The MTD was AZA 300 mg on days 1 to 14 and ROMI 14 mg/m2 on days 8, 15, and 22 on a 35-day cycle. DLTs included grade 4 thrombocytopenia, prolonged grade 3 thrombocytopenia, grade 4 neutropenia, and pleural effusion. There were no treatment-related deaths. The combination was substantially more active in patients with PTCL than in those with non-T-cell lymphoma. The overall response rate in all, non-T-cell, and T-cell lymphoma patients was 32%, 10%, and 73%, respectively, and the complete response rates were 23%, 5%, and 55%, respectively. We did not find an association between response and level of demethylation or tumor mutational profile. This study establishes that combined epigenetic modifiers are potently active in PTCL patients. This trial was registered at www.clinicaltrials.gov as NCT01998035.

Genetic and phenotypic characterization of indolent T-cell lymphoproliferative disorders of the gastrointestinal tract

Indolent T-cell lymphoproliferative disorders of the gastrointestinal tract are rare clonal T-cell diseases that more commonly occur in the intestines and have a protracted clinical course. Different immunophenotypic subsets have been described, but the molecular pathogenesis and cell of origin of these lymphocytic proliferations is poorly understood. Hence, we performed targeted next-generation sequencing and comprehensive immunophenotypic analysis of ten indolent T-cell lymphoproliferative disorders of the gastrointestinal tract, which comprised CD4⁺ (n=4), CD8⁺ (n=4), CD4⁺/CD8⁺ (n=1) and CD4^-/CD8^- (n=1) cases. Genetic alterations, including recurrent mutations and novel rearrangements, were identified in 8/10 (80%) of these lymphoproliferative disorders. The CD4⁺, CD4⁺/CD8⁺, and CD4^-/CD8^- cases harbored frequent alterations of JAK-STAT pathway genes (5/6, 82%); STAT3 mutations (n=3), SOCS1 deletion (n=1) and STAT3-JAK2 rearrangement (n=1), and 4/6 (67%) had concomitant mutations in epigenetic modifier genes (TET2, DNMT3A, KMT2D). Conversely, 2/4 (50%) of the CD8⁺ cases exhibited structural alterations involving the 3' untranslated region of the IL2 gene. Longitudinal genetic analysis revealed stable mutational profiles in 4/5 (80%) cases and acquisition of mutations in one case was a harbinger of disease transformation. The CD4⁺ and CD4⁺/CD8⁺ lymphoproliferative disorders displayed heterogeneous Th1 (T-bet⁺), Th2 (GATA3⁺) or hybrid Th1/Th2 (T-bet⁺/GATA3⁺) profiles, while the majority of CD8⁺ disorders and the CD4^-/CD8^- disease showed a type-2 polarized (GATA3⁺) effector T-cell (Tc2) phenotype. Additionally, CD103 expression was noted in 2/4 CD8⁺ cases. Our findings provide insights into the pathogenetic bases of indolent T-cell lymphoproliferative disorders of the gastrointestinal tract and confirm the heterogeneous nature of these diseases. Detection of shared and distinct genetic alterations of the JAK-STAT pathway in certain immunophenotypic subsets warrants further mechanistic studies to determine whether therapeutic targeting of this signaling cascade is efficacious for a proportion of patients with these recalcitrant diseases.

T-cell large granular lymphocyte leukemia in solid organ transplant recipients: case series and review of the literature

T-cell large granular lymphocyte (T-LGL) leukemia is a rare clonal proliferation of cytotoxic lymphocytes rarely described in solid organ transplant (SOT). We reviewed records from 656 kidney transplant recipients in follow-up at our Center from January 1998 to July 2017. In addition, we researched, through PubMed, further reports of T-LGL leukemia in SOT from March 1981 to December 2017. We identified six cases of T-LGL leukemia in our cohort of patients and 10 in the literature. This lymphoproliferative disorder was detected in one combined liver-kidney, one liver and 14-kidney transplant recipients. Median age at presentation was 46.5 years (IQR 39.2-56.9). The disease developed after a median age of 10 years (IQR 4.9-12) from transplantation. Anemia was the most common presentation (62.5%) followed by lymphocytosis (43.7%) and thrombocytopenia (31.2%). Splenomegaly was reported in 43.7% of the patients. Eight patients (50%) who experienced severe symptoms were treated with non-specific immunosuppressive agents. Six of them (75%) had a good outcome, whereas two (25%) remained red blood cell transfusion dependent. No cases progressed to aggressive T-LGL leukemia or died of cancer at the end of follow-up. These results suggest that T-LGL leukemia is a rare but potentially disruptive hematological disorder in the post-transplant period.

Immunodeficiency-associated lymphoproliferative disorders: time for reappraisal?

Immunodeficiency-associated lymphoproliferative disorders (IA-LPDs) are pathologically and clinically heterogeneous. In many instances, similar features are shared by a spectrum of IA-LPDs in clinically diverse settings. However, the World Health Organization (WHO) classifies IA-LPDs by their immunodeficiency setting largely according to the paradigm of posttransplant lymphoproliferative disorders but with inconsistent terminology and disease definitions. The field currently lacks standardization and would greatly benefit from thinking across immunodeficiency categories by adopting a common working vocabulary to better understand these disorders and guide clinical management. We propose a 3-part unifying nomenclature that includes the name of the lesion, associated virus, and the specific immunodeficiency setting for all IA-LPDs. B-cell lymphoproliferative disorders (LPDs) are usually Epstein-Barr virus (EBV)⁺ and show a spectrum of lesions, including hyperplasias, polymorphic LPDs, aggressive lymphomas, and, rarely, indolent lymphomas. Human herpes virus 8-associated LPDs also include polyclonal and monoclonal proliferations. EBV^- B-cell LPDs and T- and NK-cell LPDs are rare and less well characterized. Recognition of any immunodeficiency is important because it impacts the choice of treatment options. There is an urgent need for reappraisal of IA-LPDs because a common framework will facilitate meaningful biological insights and pave the way for future work in the field.

Sezary syndrome manifesting as posttransplant lymphoproliferative disorder

Posttransplant lymphoproliferative disorders (PTLDs) of T-cell orgin are rare biologically heterogeneous diseases of mature lymphoid cells manifesting in immunosuppressed patients. Only a few cases of mycosis fungoides diagnosed post allogeneic hematopoietic cell transplant (alloHSCT) have been described so far. We present a patient with myelodysplastic syndrome (MDS) post matched unrelated donor alloHSCT who was on long-term immunosuppressive therapy due to graft versus host disease. Three years after an alloHSCT, she developed generalized erythroderma and peripheral blood lymphocytosis. Both skin biopsy and peripheral blood flow cytometry revealed atypical CD4+ T-cell population consistent with diagnosis of Sezary syndrome. Chimerism studies revealed 100% donor engraftment. Therapy with extracorporeal photopheresis resulted in complete response in blood and skin.

An Unusual Posttransplant T-cell Lymphoma After Liver Transplantation: A Case Report

Posttransplantation lymphoproliferative disorders (PTLDs) encompass a spectrum of heterogeneous entities ranging from benign lymphocytic proliferations to high-grade malignant lymphomas. The majority of PTLDs are associated with reactivation of Epstein-Barr virus (EBV), which induces B-cell proliferation and occurs in the setting of severe immune suppression after solid organ or bone marrow transplantation. T-cell/natural killer cell PTLDs are relatively rare, constituting ∼15% of all cases. T-cell PTLDs are usually aggressive, and outcomes are poor. This article describes an unusual case of T-cell PTLD with a favorable outcome. The patient is a 57-year-old man who underwent a liver transplantation due to hepatitis C cirrhosis. He developed graft-versus-host disease with skin and gastrointestinal involvement and generalized lymphadenopathy 4 months after transplantation. Histologic sections of an excised axillary lymph node showed atypical medium and larger T-lymphocytes that were positive for CD3, CD5, CD43, and CD8 but were negative for B-cell antigens, CD56, and in situ hybridization for EBV-encoded RNA. Polymerase chain reaction analysis revealed monoclonal T-cell receptor gamma chain gene rearrangement. A diagnosis of high-grade T-cell PTLD was made. The patient was treated with 4 cycles of cyclophosphamide, doxorubicin, vincristine, and prednisone and is currently in remission, 4 years after therapy. The rapid presentation of an EBV-negative T-cell PTLD with a nonaggressive course and complete response to treatment is an unusual presentation of posttransplantation T-cell lymphoma, which is usually associated with a high mortality rate.

Overlap at the molecular and immunohistochemical levels between angioimmunoblastic T-cell lymphoma and a subgroup of peripheral T-cell lymphomas without specific morphological features

The overlap of morphology and immunophenotype between angioimmunoblastic T-cell lymphoma (AITL) and other nodal peripheral T-cell lymphomas (n-PTCLs) is a matter of current interest whose clinical relevance and pathogenic background have not been fully established. We studied a series of 98 n-PTCL samples (comprising 57 AITL and 41 PTCL-NOS) with five T_FH antibodies (CD10, BCL-6, PD-1, CXCL13, ICOS), looked for mutations in five of the genes most frequently mutated in AITL (TET2, DNMT3A, IDH2, RHOA and PLCG1) using the Next-Generation-Sequencing Ion Torrent platform, and measured the correlations of these characteristics with morphology and clinical features. The percentage of mutations in the RHOA and TET2 genes was similar (23.5% of cases). PLCG1 was mutated in 14.3%, IDH2 in 11.2% and DNMT3A in 7.1% of cases, respectively. In the complete series, mutations in RHOA gene were associated with the presence of mutations in IDH2, TET2 and DNMT3A (p < 0.001, p = 0.043, and p = 0.029, respectively). Fourteen cases featured RHOA mutations without TET2 mutations. A close relationship was found between the presence of these mutations and a T_FH-phenotype in AITL and PTCL-NOS patients. Interestingly, BCL-6 expression was the only T_FH marker differentially expressed between AITL and PTCL-NOS cases. There were many fewer mutated cases than there were cases with a T_FH phenotype. Overall, these data suggest alternative ways by which neoplastic T-cells overexpress these proteins. On the other hand, no clinical or survival differences were found between any of the recognized subgroups of patients with respect to their immunohistochemistry or mutational profile.

Orchestration of H3K27 methylation: mechanisms and therapeutic implication

Histone proteins constitute the core component of the nucleosome, the basic unit of chromatin. Chemical modifications of histone proteins affect their interaction with genomic DNA, the accessibility of recognized proteins, and the recruitment of enzymatic complexes to activate or diminish specific transcriptional programs to modulate cellular response to extracellular stimuli or insults. Methylation of histone proteins was demonstrated 50 years ago; however, the biological significance of each methylated residue and the integration between these histone markers are still under intensive investigation. Methylation of histone H3 on lysine 27 (H3K27) is frequently found in the heterochromatin and conceives a repressive marker that is linked with gene silencing. The identification of enzymes that add or erase the methyl group of H3K27 provides novel insights as to how this histone marker is dynamically controlled under different circumstances. Here we summarize the methyltransferases and demethylases involved in the methylation of H3K27 and show the new evidence by which the H3K27 methylation can be established via an alternative mechanism. Finally, the progress of drug development targeting H3K27 methylation-modifying enzymes and their potential application in cancer therapy are discussed.

Mutational landscape of B-cell post-transplant lymphoproliferative disorders

It is currently unclear whether post-transplant diffuse large B-cell lymphomas (PT-DLBCL) display a similar genomic landscape as DLBCL in immunocompetent patients (IC-DLBCL). We investigated 50 post-transplant lymphoproliferative disorders (PTLDs) including 37 PT-DLBCL samples for somatic mutations frequently observed in IC-DLBCL. Targeted Next Generation Sequencing (NGS) using the Ion Torrent platform and a customized panel of 68 genes was performed on genomic DNA. Non-tumoural tissue was sequenced to exclude germline variants in cases where available. A control cohort of 76 IC-DLBCL was available for comparative analyses. In comparison to IC-DLBCLs, PT-DLBCL showed more frequent mutations of TP53 (P = 0·004), and absence of ATM and B2M mutations (P = 0·004 and P = 0·016, respectively). In comparison to IC-DLBCLs, Epstein-Barr virus (EBV)⁺ PT-DLBCL had fewer mutated genes (P = 0·007) and particularly fewer mutations in nuclear factor-κB pathway-related genes (P = 0·044). TP53 mutations were more frequent in EBV^- PT-DLBCL as compared to IC-DLBCL (P = 0·001). Germinal centre B cell (GCB) subtype of PT-DLBCL had fewer mutations and mutated genes than GCB-IC-DLBCLs (P = 0·048 and 0·04 respectively). Polymorphic PTLD displayed fewer mutations as compared to PT-DLBCL (P = 0·001). PT-DLBCL differs from IC-DLBCL with respect to mutations in genes related to DNA damage control and immune-surveillance, and EBV association is likely to have a bearing on the mutational pattern.