Early posttransplant lymphoproliferative disease: clinicopathologic features and correlation with mTOR signaling pathway activation

The IPTA Nashville consensus conference on post-transplant lymphoproliferative disorders after solid organ transplantation in children: IV-consensus guidelines for the management of post-transplant lymphoproliferative disorders in children and adolescents

The International Pediatric Transplant Association convened an expert consensus conference to assess current evidence and develop recommendations for various aspects of care relating to post-transplant lymphoproliferative disorders (PTLD) after pediatric solid organ transplantation. This report addresses the outcomes of deliberations by the PTLD Management Working Group. A strong recommendation was made for reduction in immunosuppression as the first step in management. Similarly, strong recommendations were made for the use of the anti-CD20 monoclonal antibody (rituximab) as was the case for chemotherapy in selected scenarios. In some scenarios, there is uncoupling of the strength of the recommendations from the available evidence in situations where such evidence is lacking but collective clinical experiences drive decision-making. Of note, there are no large, randomized phase III trials of any treatment for PTLD in the pediatric age group. Current gaps and future research priorities are highlighted.

A Pathology Experience of Posttransplant Lymphoproliferative Disorder From One Tertiary Hospital: Pathology Concepts and Diagnostic Approach

BACKGROUND

Solid organ transplantation and bone marrow/hematologic stem cell transplantation recipients face a heightened risk of developing malignancies or cancer as a result of immunosuppression. Posttransplant lymphoproliferative disorders (PTLD) are a range of disorders from benign lymphoid growth to lymphoma found post-transplant. Risk factors for PTLD include high immunosuppressive use and oncogenic effects of Epstein-Barr virus (EBV). There is a lack of comprehensive clinical and pathological documentation of PTLD cases among Saudi patients, and the available data are limited to a few case reports. As a result, a deeper understanding of this disease requires more clinicopathological information.

MATERIAL AND METHOD

In this review, we share our insights on cases diagnosed with PTLD at King Faisal Specialist Hospital and Research Center, a prominent tertiary center in the western region of Saudi Arabia, from 2005-2023.

RESULT

We have diagnosed a total of 14 cases of PTLD in our department, with an age range spanning from 3 to 62 years. These diagnoses were made based on biopsies or tumor resection procedures. The survival rate of patients is believed to be influenced by multiple factors, including histology, tumorigenesis, disease biology, and clinical stage. Additionally, Kaplan-Meier curve analysis indicates that female patients tend to have a higher estimated survival rate compared to males.

CONCLUSION

PTLD diagnosis and therapy have greatly improved in the past 20 years. PTLD is treated with reduced immunosuppression, rituximab, chemotherapy, adoptive therapy, surgery, antiviral therapy, and radiotherapy. In this study, we present our experience from a large tertiary center in the western region of Saudi Arabia. Moreover, we will go through etiology, clinical features, and pathologic morphology along with the corresponding genetics, prevention, and valid treatment options.

The pathobiology of select adolescent young adult lymphomas

Lymphoid cancers are among the most frequent cancers diagnosed in adolescents and young adults (AYA), ranging from approximately 30%-35% of cancer diagnoses in adolescent patients (age 10-19) to approximately 10% in patients aged 30-39 years. Moreover, the specific distribution of lymphoid cancer types varies by age with substantial shifts in the subtype distributions between pediatric, AYA, adult, and older adult patients. Currently, biology studies specific to AYA lymphomas are rare and therefore insight into age-related pathogenesis is incomplete. This review focuses on the paradigmatic epidemiology and pathogenesis of select lymphomas, occurring in the AYA patient population. With the example of posttransplant lymphoproliferative disorders, nodular lymphocyte-predominant Hodgkin lymphoma, follicular lymphoma (incl. pediatric-type follicular lymphoma), and mediastinal lymphomas (incl. classic Hodgkin lymphoma, primary mediastinal large B cell lymphoma and mediastinal gray zone lymphoma), we here illustrate the current state-of-the-art in lymphoma classification, recent molecular insights including genomics, and translational opportunities. To improve outcome and quality of life, international collaboration in consortia dedicated to AYA lymphoma is needed to overcome challenges related to siloed biospecimens and data collections as well as to develop studies designed specifically for this unique population.

Post-transplant lymphoproliferative disorders (PTLD) in adolescents and young adults: A category in need of definition

Post-transplant lymphoproliferative disorders are a well-recognized complication of solid organ and stem cell transplantation. Much data has accumulated with respect to the pathobiology and clinical behavior of these lesions in the general post-transplant population as well as in the pediatric and adult age groups. However, information as to these lesions in the adolescent and young adult populations, which bridge the pediatric and adult groups, is limited. In this review, the focus is on this unique population of PTLD patients and their proliferations.

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.

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.

Characterization and outcome of post-transplant lymphoproliferative disorders within a collaborative study

Background

Post-transplant lymphoproliferative disorders (PTLD) are heterogeneous lymphoid disorders ranging from indolent polyclonal proliferations to aggressive lymphomas that can arise after solid organ transplantation (SOT) and allogeneic hematopoietic transplantation (allo-HSCT).

Methods

In this multi-center retrospective study, we compare patient characteristics, therapies, and outcomes of PTLD after allo-HSCT and SOT. Twenty-five patients (15 after allo-HSCT and 10 after SOT) were identified who developed PTLD between 2008 and 2022.

Results

Median age (57 years; range, 29-74 years) and baseline characteristics were comparable between the two groups (allo-HSCT vs SOT), but median onset of PTLD was markedly shorter after allo-HSCT (2 months vs. 99 months, P<0.001). Treatment regimens were heterogeneous, with reduction of immunosuppression in combination with rituximab being the most common first-line treatment strategy in both cohorts (allo-HSCT: 66%; SOT: 80%). The overall response rate was lower in the allo-HSCT (67%) as compared to the SOT group (100%). Consequently, the overall survival (OS) trended towards a worse outcome for the allo-HSCT group (1-year OS: 54% vs. 78%; P=0.58). We identified PTLD onset ≤150 days in the allo-HSCT (P=0.046) and ECOG >2 in the SOT group (P=0.03) as prognostic factors for lower OS.

Conclusion

PTLD cases present heterogeneously and pose unique challenges after both types of allogeneic transplantation.

Post-transplant lymphoproliferative disease in children, adolescents, and young adults

Post-transplant lymphoproliferative disease (PTLD) remains a major complication of transplantation. PTLD is a rare entity and very heterogenous making consensus on diagnosis and treatment very challenging. The majority are Epstein-Barr virus (EBV) driven, CD20+ B-cell proliferations. PTLD does occur following hematopoietic stem cell transplant (HSCT), but due to the relative short risk period and efficacy of pre-emptive therapy, PTLD following HSCT will not be discussed in this review. This review will focus on the epidemiology, role of EBV, clinical presentation, diagnosis and evaluation and the current and emerging treatment strategies for pediatric PTLD following solid organ transplantation.

Relationship of Post-Transplant Lymphoproliferative Disorders (PTLD) Subtypes and Clinical Outcome in Pediatric Heart Transplant Recipients: A Retrospective Single Institutional Analysis/Experience of 558 Patients

Post-transplant lymphoproliferative disorders (PTLD) are heterogenous lymphoproliferative disorders that develop as a consequence of immunosuppression in transplant recipients. We sought to determine if subtypes of PTLD correlated with different outcomes. We performed a retrospective review of PTLD occurring in pediatric heart transplant recipients. A total of 558 children and infants underwent cardiac transplantation at our institution between 1985 and 2019 and were followed until March 2021. Forty-nine of 558 patients developed PTLD (8.8%). As compared to older children (>one year of age), infant recipients (<three months of age) were less likely to develop PTLD. Monomorphic PTLDs (M-PTLD, 61%) was the most common subtype at initial diagnosis, followed by non-destructive (21%), polymorphic (14%), and classic Hodgkin lymphoma (cHL, 4%). Patients who underwent transplantation at a young age (<three months) had significantly lower rates of M-PTLD or cHL and a longer time from transplant to PTLD diagnosis as compared to children older than one year at transplant (p = 0.04). Although not reaching statistical significance, patients with a shorter time to PTLD diagnosis showed a trend toward higher rates of M-PTLD or cHL. As expected, the overall survival (OS) of patients with M-PTLD or cHL was significantly lower than patients with non-destructive or polymorphic PTLD.

Non-Hodgkin lymphoma after pediatric kidney transplantation

Non-Hodgkin lymphoma (NHL) that develops after kidney transplantation belongs to post-transplant lymphoproliferative disorders (PTLD) occurring with an incidence of 2-3%. Most pediatric cases are related to primary infection with Epstein-Barr virus (EBV), able to transform and immortalize B cells and widely proliferate due to the lack of relevant control of cytotoxic T cells in patients receiving post-transplant immunosuppression. NHL may develop as a systemic disease or as a localized lesion. The clinical pattern is variable, from non-symptomatic to fulminating disease. Young age of transplant recipient, seronegative EBV status at transplantation, and EBV mismatch between donor and recipient (D+/R-) are regarded as risk factors. Immunosuppression impacts the development of both early and late NHLs. Specific surveillance protocols, including monitoring of EBV viral load, are used in patients at risk; however, detailed histopathology diagnosis and evaluation of malignancy staging is crucial for therapeutic decisions. Minimizing of immunosuppression is a primary management, followed by the use of rituximab in B-cell NHLs. Specific chemotherapeutic protocols, adjusted to lymphoma classification and staging, are used in advanced NHLs. Radiotherapy and/or surgical removal of malignant lesions is limited to the most severe cases. Outcome is variable, depending on risk factors and timing of diagnosis, however is positive in pediatric patients in terms of graft function and patient survival. Kidney re-transplantation is possible in survivors who lost the primary graft due to chronic rejection, however may be performed after at least 2-3 years of waiting time, careful verification of malignancy-free status, and gaining immunity against EBV.

Recurrent, Multisubtype Posttransplant Lymphoproliferative Disorder Masquerading as Inflammatory Bowel Disease

Posttransplant lymphoproliferative disorder (PTLD) is a severe posttransplant complication that occurs because of immunosuppression within the first year; however, recurrent PTLD or development of multiple histologic subtypes are rare. Our case demonstrates a renal transplant recipient with rare, recurrent PTLD with multiple histologic subtypes (monomorphic and polymorphic PTLD) despite a previous response to rituximab and resolution of inflammatory changes on endoscopy. It is essential that clinicians maintain a high suspicion for PTLD when caring for patients with previous transplantation and that they have a lower threshold for biopsy with endoscopic findings of nonspecific inflammatory changes.

EBV-Driven Lymphoproliferative Disorders and Lymphomas of the Gastrointestinal Tract: A Spectrum of Entities with a Common Denominator (Part 3)

EBV is the first known oncogenic virus involved in the development of several tumors. The majority of the global population are infected with the virus early in life and the virus persists throughout life, in a latent stage, and usually within B lymphocytes. Despite the worldwide diffusion of EBV infection, EBV-associated diseases develop in only in a small subset of individuals often when conditions of immunosuppression disrupt the balance between the infection and host immune system. EBV-driven lymphoid proliferations are either of B-cell or T/NK-cell origin, and range from disorders with an indolent behavior to aggressive lymphomas. In this review, which is divided in three parts, we provide an update of EBV-associated lymphoid disorders developing in the gastrointestinal tract, often representing a challenging diagnostic and therapeutic issue. Our aim is to provide a practical diagnostic approach to clinicians and pathologists who face this complex spectrum of disorders in their daily practice. In this part of the review, the chronic active EBV infection of T-cell and NK-cell type, its systemic form; extranodal NK/T-cell lymphoma, nasal type and post-transplant lymphoproliferative disorders are discussed.

Pitfalls in gastrointestinal tract haematopoietic lesions

Specimens from the gastrointestinal (GI) tract are among the most commonly encountered in routine pathology practice worldwide. It is well known that the luminal GI tract is home to various areas rich in mucosa-associated lymphoid tissue (MALT), whether native or acquired. The latter may be particularly problematic due to its well-known predisposing factors such as Helicobacter pylori infection and autoimmune conditions. Nevertheless, native GI structures are often the subject of query, particularly in conditions that may mimic lymphoproliferative conditions, including infectious and inflammatory diseases. Herein, we describe and share common clinicopathological findings in our daily practice that are challenging to distinguish from subtle low-grade neoplastic lymphoproliferative disorders.

A Clinicopathological Study of Cytomegalovirus Lymphadenitis and Tonsillitis and Their Association with Epstein-Barr Virus

Introduction

Histopathological characteristics of cytomegalovirus (CMV) lymphadenitis have been well described. Rare studies have reported the immune status and clinical features. Clinically, experts believed that CMV lymphadenitis develops in immunocompromised and immunocompetent patients. Infectious mononucleosis (IM)-like syndrome is the most well-known clinical presentation.

Methods

We reviewed archived CMV immunohistochemical stains on lymphoid tissues. The clinicopathological features of CMV-positive cases were studied.

Results

For lymph nodes, we detected CMV in 29% (5/17) allogeneic peripheral blood hematopoietic stem cell transplantation (PBSCT) recipients, 29% (4/14) post-autologous PBSCT patients, 13% (6/47) patients treated with intravenous chemotherapy, and 9% (9/96) immunocompetent patients. We detected CMV in 7% (2/24) of tonsils but not in the nasopharynx, tongue base, or spleen specimens. The patients with iatrogenic immunodeficiency ranged from 37 to 76 years old. CMV infections developed a few years after lymphoma treatment (median duration after allogeneic PBSCT, 932 days; after autologous PBSCT, 370 days; and after chemotherapy, 626 days). The most common clinical presentation was neck mass (13/25, 42%), followed by asymptomatic image finding (10/25, 40%). Positron emission tomography/computed tomography (PET/CT) scan showed increased uptake compared to the liver in all patients (11/11, 100%). Of 10 lymphoma patients, 8 (80%) had a Deauville score of 4–5; they accounted for 30% (8/27) of lymphoma patients with false-positive PET/CT scan results. All cases were self-limiting. 96% (23/25) cases had Epstein–Barr virus coinfection, and EBER-positive cells were predominantly in a few germinal centers.

Conclusions

Cytomegalovirus (CMV) lymphadenitis and tonsillitis were subclinical infections, not primary CMV infection with IM-like syndrome. The lymphadenopathy typically developed a few years after lymphoma treatments in the middle-aged and the elderly. The lesions mimicked lymphoma relapse in PET scans. Therefore, recognizing CMV infection in lymphoid tissues is of clinical importance.

Graphic abstract

Classic Hodgkin lymphoma post-transplant lymphoproliferative disorders (PTLD) are often preceded by discordant PTLD subtypes

Classic Hodgkin lymphoma (CHL) is the rarest post-transplant lymphoproliferative disorder (PTLD) subtype. Few cases of patients with metachronous discordant PTLD episodes including CHL-PTLD have been reported, but the incidence of and risk factors for this phenomenon are unknown. Patients with CHL-PTLD were identified from an institutional PTLD database. Of 13 patients identified with CHL-PTLD six (46%) had antecedent non-CHL-PTLD: three had polymorphic PTLD, two monomorphic PTLD, and one nondestructive PTLD. Patients with prior metachronous non-CHL-PTLD were younger at transplant and had a longer latency time to CHL-PTLD post-transplant. The prevalence of EBV seronegativity at transplant was high in both groups, but prolonged high-level EBV DNAemia only occurred in some with metachronous non-CHL-PTLD. In conclusion, patients with CHL-PTLD have metachronous non-CHL-PTLD diagnoses with discordant histology more commonly than previously recognized. Primary EBV infection with chronically elevated EBV viral loads may represent unique risk factors for CHL-PTLD following an initial non-CHL-PTLD event.

Atypical malignancies after intestinal transplantation in children: A European single-centre experience

BACKGROUND

Post-transplant malignancies, that is, lymphomas, are a recognized complication in intestinal transplant recipients but are mostly secondary to EBV infection. There is an increased risk for malignancies in unusual sites in intestinal transplant recipients as compared to other solid organ transplants and the general population.

OBJECTIVE

To evaluate the incidence, course, and outcome of unusual malignancies in children after ITx.

METHODS

Retrospective analysis of children who underwent ITx for primary digestive disorders at Birmingham Children's Hospital between January 1989 and December 2017.

RESULTS

Ninety-eight intestinal transplants were performed in 90 children (49 males and 41 females) with an underlying primary digestive disorder. Median age was 2.7 years (0.6-16.2), and median weight was 14.5 kg (5.7-53.2) at the time of transplant. Within this cohort, we identified four cases of unusual malignancies at rare sites of presentation. One patient developed cerebral PTLD, two patients were diagnosed with SMT, located at the stomal orifice and in cervicothoracic paravertebral area, respectively, and the last patient developed a retroperitoneal angiosarcoma. Unfortunately, the overall patient outcome was poor in all but one child with SMT, who currently survives with cytotoxic T-cell therapy.

CONCLUSION

Unusual malignancies can occur in approximately 5% of children following ITx. A high index of suspicion is required for a timely diagnosis and adequate treatment.

Methotrexate-associated Lymphoproliferative Disorders in Patients With Rheumatoid Arthritis: Clinicopathologic Features and Prognostic Factors

Methotrexate (MTX) carries a risk of lymphoproliferative disorders (LPDs), but MTX-associated LPDs (MTX-LPDs) can resolve spontaneously after MTX withdrawal. However, the precise clinicopathologic features of MTX-LPD remain unclear. We aimed to investigate the clinicopathologic characteristics, outcomes, and prognostic factors for histologic types of MTX-LPD. Paraffin-embedded tissue samples of 219 patients with MTX-LPD were analyzed. In total, 30,33,106, and 26 had reactive lymphoid hyperplasia (RH), polymorphic-LPD (Poly-LPD), diffuse large B-cell lymphomas (DLBCLs), and classic Hodgkin lymphoma (CHL), respectively. The clinicopathologic features of RH, Poly-LPD, DLBCLs, and CHL were as follows: extranodal involvement: 13.8% (4/29), 36.4% (12/33), 69.5% (73/105), and 15.4% (4/26); Epstein-Barr virus encoded RNA positivity: 55.2% (16/29), 71.9% (23/32), 45.3% (48/106), and 76.9% (20/26); necrosis: 0% (0/29), 51.5% (17/33), 34.3% (36/105), and 12.0% (3/25); and Hodgkin Reed-Sternberg-like cells: 17.2% (5/29), 50% (14/28), and 19.8% (21/106). The median duration from MTX withdrawal to the time of disease regression was 10.4, 3.0, 4.2, and 2.7 months for RH, Poly-LPD, DLBCLs, and CHL. After MTX withdrawal, progression-free survival was the greatest for RH, followed by for Poly-LPD, DLBCL, and CHL (all P<0.05). Overall survival did not differ significantly between the groups. On univariate analysis, the predictive factors for progression-free survival included plasma cell infiltrate for CHL, eosinophil infiltrate, age above 70 years, and extensive necrosis for Poly-LPD, while they were Epstein-Barr virus encoded RNA positivity and International Prognostic Index risk for DLBCL on multivariate analysis. In conclusion, histologic categorization and histology-specific factors could be useful for predicting MTX-LPD progression after MTX withdrawal.

Diagnostic performance of FDG-PET/CT of post-transplant lymphoproliferative disorder and factors affecting diagnostic yield

Purpose

Post-transplant lymphoproliferative disorder (PTLD) is a serious complication after solid organ and hematopoietic stem cell transplantation, requiring a timely and accurate diagnosis. In this study, we evaluated the diagnostic performance of FDG-PET/CT in patients with suspected PTLD and examined if lactate dehydrogenase (LDH) levels, Epstein-Barr virus (EBV) load, or timing of FDG-PET/CT relate to detection performance of FDG-PET/CT.

Methods

This retrospective study included 91 consecutive patients with clinical suspicion of PTLD and a total of 97 FDG-PET/CT scans within an 8-year period. Pathology reports and a 2-year follow-up were used as the reference standard. Diagnostic performance of FDG-PET/CT for detection of PTLD as well as logistic regression analysis for factors expected to affect diagnostic yield were assessed.

Results

The diagnosis of PTLD was established in 34 patients (35%). Fifty-seven FDG-PET/CT scans (59%) were true negative, 29 (30%) were true positive, 6 (6%) false positive, and 5 (5%) false negative. Sensitivity of FDG-PET/CT for the detection of PTLD was 85%, specificity 90%, positive predictive value 83%, and negative predictive value 92%, with good inter-observer variability (k = 0.78). Of the parameters hypothesized to be associated with a true positive FDG-PET/CT result for the diagnosis of PTLD, only LDH was statistically significant (OR 1.03, p = 0.04).

Conclusion

FDG-PET/CT has a good diagnostic performance in patients suspected of PTLD, with a good inter-observer agreement. Only LDH levels seemed to influence the detection performance of FDG-PET/CT. EBV-DNA load and timing of FDG-PET/CT after transplantation did not affect FDG-PET/CT diagnostic yield.

EBV-Associated Lymphoproliferative Disorders: Update in Classification

Although about 90% of the world's population is infected by EBV only a small subset of the related infections result in neoplastic transformation. EBV is a versatile oncogenic agent involved in a multitude of hematopoietic, epithelial, and mesenchymal neoplasms, but the precise role of EBV in the pathogenesis of many of the associated lymphoid/histiocytic proliferations remains hypothetical or not completely understood. Additional studies and use of evolving technologies such as high-throughput next-generation sequencing may help address this knowledge gap and may lead to enhanced diagnostic assessment and the development of potential therapeutic interventions.

Dual blockade of the PI3K/Akt/mTOR pathway inhibits posttransplant Epstein-Barr virus B cell lymphomas and promotes allograft survival

Posttransplant lymphoproliferative disorder (PTLD) is a serious complication of organ transplantation that often manifests as Epstein-Barr virus (EBV)-associated B cell lymphomas. Current treatments for PTLD have limited efficacy and can be associated with graft rejection or systemic toxicities. The mTOR inhibitor, rapamycin, suppresses tumor growth of EBV+ B cell lymphoma cells in vitro and in vivo; however, the efficacy is limited and clinical benefits of mTOR inhibitors for PTLD are variable. Here, we show constitutive activation of multiple nodes within the PI3K/Akt/mTOR pathway in EBV+ PTLD-derived cell lines. Inhibition of either PI3K or Akt, with specific inhibitors CAL-101 and MK-2206, respectively, diminished growth of EBV+ B cell lines from PTLD patients in a dose-dependent manner. Importantly, rapamycin combined with CAL-101 or MK-2206 had a synergistic effect in suppressing cell growth as determined by IC₅₀ isobolographic analysis and Loewe indices. Moreover, these combinations were significantly more effective than rapamycin alone in inhibiting tumor xenograft growth in NOD-SCID mice. Finally, both CAL-101 and MK-2206 also prolonged survival of heterotopic cardiac allografts in C57BL/6 mice. Thus, combination therapy with rapamycin and a PI3K inhibitor, or an Akt inhibitor, can be an efficacious treatment for EBV-associated PTLD, while simultaneously promoting allograft survival.

The Tumor Microenvironment in Post-Transplant Lymphoproliferative Disorders

Post-transplant lymphoproliferative disorders (PTLDs) cover a broad spectrum of lymphoproliferative lesions arising after solid organ or allogeneic hematopoietic stem cell transplantation. The composition and function of the tumor microenvironment (TME), consisting of all non-malignant constituents of a tumor, is greatly impacted in PTLD through a complex interplay between 4 factors: 1) the graft organ causes immune stimulation through chronic antigen presentation; 2) the therapy to prevent organ rejection interferes with the immune system; 3) the oncogenic Epstein-Barr virus (EBV), present in 80% of PTLDs, has a causative role in the oncogenic transformation of lymphocytes and influences immune responses; 4) interaction with the donor-derived immune cells accompanying the graft. These factors make PTLDs an interesting model to look at cancer-microenvironment interactions and current findings can be of interest for other malignancies including solid tumors. Here we will review the current knowledge of the TME composition in PTLD with a focus on the different factors involved in PTLD development.

Epstein-Barr virus (EBV)-associated lymphoid proliferations, a 2018 update

Epstein-Barr virus (EBV) has been linked to many human neoplasms including hematopoietic, epithelial, and mesenchymal tumors. Since our original review of EBV-associated lymphoproliferative disorders in 2007, many advances and developments have been reported. In this review, we will examine the recent advances in EBV-associated lymphoid/histiocytic proliferations, dividing them into reactive, B cell, T/NK cell, immunodeficiency-related, and histiocytic/dendritic cell proliferations.

Dasatinib-related Follicular Hyperplasia: An Underrecognized Entity With Characteristic Morphology

Dasatinib, a second-generation tyrosine kinase inhibitor with activity against BCR-ABL1 and other Src family tyrosine kinases, is approved as a first-line treatment option for Philadelphia chromosome-positive chronic myelogenous leukemia (CML) in the chronic phase. Recently, lymphadenopathy with morphologic features of reactive follicular hyperplasia was described in a cohort of patients with CML on long-term dasatinib therapy. However, the complete morphologic and immunophenotypic features of this previously underappreciated adverse effect have not been fully described. Herein, we report 3 cases of unexplained lymphadenopathy resulting in multiple diagnostic procedures in patients with CML and a history of long-term dasatinib therapy. Morphologic examination demonstrated preserved nodal architecture showing hybrid features of progressive transformation of germinal centers and Castleman-type changes in a background of florid follicular hyperplasia. Large germinal centers were disrupted by complex infolding of IgD+ mantle zones arranged as cuffs surrounding perforating capillaries. Other abnormalities variably present included decreased CD20 expression among polytypic B cells and increased Epstein-Barr virus reactivity in scattered paracortical cells and/or individual germinal centers. B-cell clonality studies showed no predominant clonal rearrangements. Consideration of dasatinib-related lymphadenopathy may pre-empt unnecessary repeat diagnostic procedures in patients with CML or other dasatinib-susceptible malignancies and persistent lymphadenopathy.

Effects of mTOR and calcineurin inhibitors combined therapy in Epstein-Barr virus positive and negative Burkitt lymphoma cells

Post-transplant lymphoproliferative disorder is a severe complication in solid organ transplant recipients, which is highly associated with Epstein-Barr virus infection in pediatric patients and occasionally presents as Burkitt- or Burkitt-like lymphoma. The mammalian target of rapamycin (mTOR) pathway has been described as a possible antitumor target whose inhibition may influence lymphoma development and proliferation after pediatric transplantation. We treated Epstein-Barr virus positive (Raji and Daudi) and negative (Ramos) human Burkitt lymphoma derived cells with mTOR inhibitor everolimus alone and in combination with clinically relevant immunosuppressive calcineurin inhibitors (tacrolimus or cyclosporin A). Cell proliferation, toxicity, and mitochondrial metabolic activity were analyzed. The effect on mTOR Complex 1 downstream targets p70 S6 kinase, eukaryotic initiation factor 4G, and S6 ribosomal protein activation was also investigated. We observed that treatment with everolimus alone significantly decreased Burkitt lymphoma cell proliferation and mitochondrial metabolic activity. Everolimus in combination with cyclosporin A had a stronger suppressive effect in Epstein-Barr virus negative but not in Epstein-Barr virus positive cells. In contrast, tacrolimus completely abolished the everolimus-mediated suppressive effects. Moreover, we showed a significant decrease in activation of mTOR Complex 1 downstream targets after treatment with everolimus that was attenuated when combined with tacrolimus, but not with cyclosporin A. For the first time we showed the competitive effect between everolimus and tacrolimus when used as combination therapy on Burkitt lymphoma derived cells. Thus, according to our in vitro data, the combination of calcineurin inhibitor cyclosporin A with everolimus is preferred to the combination of tacrolimus and everolimus.

Post-transplant lymphoproliferative disease (PTLD): risk factors, diagnosis, and current treatment strategies

Post-transplant lymphoproliferative diseases (PTLD) are heterogeneous lymphoid disorders ranging from indolent polyclonal proliferations to aggressive lymphomas that complicate solid organ or hematopoietic transplantation. Risk factors for PTLD include viral infections, degree of immunosuppression, recipient age and race, allograft type, and host genetic variations. Clinically, extra-nodal disease is common including 10-15 % presenting with central nervous system (CNS) disease. Most PTLD cases are B cell (5-10 % T/NK cell or Hodgkin lymphoma), while over one-third are EBV-negative. World Health Organization (WHO) diagnostic categories are: early lesions, polymorphic, and monomorphic PTLD; although in practice, a clear separation is not always possible. Therapeutically, reduction in immunosuppression remains a mainstay, and recent data has documented the importance of rituximab +/- combination chemotherapy. Therapy for primary CNS PTLD should be managed according to immunocompetent CNS paradigms. Finally, novel treatment strategies for PTLD have emerged, including adoptive immunotherapy and rational targeted therapeutics (e.g., anti-CD30 based therapy and downstream signaling pathways of latent membrane protein-2A).

EBV-related lymphomas: new approaches to treatment

In the treatment of Epstein-Barr virus (EBV)-related lymphomas, there are few therapies specifically targeted against the latent virus within these tumors; in most cases the treatment approach is not different than the approach to EBV-negative lymphomas. Nonetheless, current and emerging therapies focused on exploiting aspects of EBV biology may offer more targeted strategies for EBV-positive lymphomas in the future. Conceptually, EBV-specific approaches include bolstering the antiviral/antitumor immune response with vaccines or EBV-specific cytotoxic T-lymphocytes, activating lytic viral genes to render the tumor cells susceptible to antiviral therapies, and inhibiting the downstream prosurvival or antiapoptotic pathways that may be activated by latent EBV proteins. EBV-specific cytotoxic T-cell infusions have proven effective in EBV-related posttransplantation lymphoproliferative disorder (EBV-PTLD) and expanding such adoptive immunotherapies to other EBV-related malignancies is an area of active research. However, other EBV-related lymphomas typically have more restricted, less immunogenic arrays of viral antigens to therapeutically target with adoptive immunotherapy compared with EBV-PTLD. Furthermore, the malignant EBV-positive tumor cells of Hodgkin lymphoma are scattered amid a dense infiltrate of regulatory T-cells, macrophages, and other cells that may dampen the antitumor efficacy of adoptive immunotherapy. Strategies to overcome these obstacles are areas of ongoing preclinical and clinical investigations. Some emerging approaches to EBV-related lymphomas include the coupling of agents that induce lytic viral replication with antiherpesvirus agents, or the use of small molecule inhibitors that block signaling pathways that are constitutively activated by EBV. EBV vaccines seem most promising for the treatment or prevention of EBV-related malignancies, rather than the prevention of primary EBV infection. EBV vaccine trials in patients with residual or low-bulk EBV-related malignancies or for the prevention of EBV-PTLD in EBV-seronegative patients awaiting solid organ transplantation are ongoing.

Posttransplant lymphoproliferative disease after pediatric solid organ transplantation

Patients after solid organ transplantation (SOT) carry a substantially increased risk to develop malignant lymphomas. This is in part due to the immunosuppression required to maintain the function of the organ graft. Depending on the transplanted organ, up to 15% of pediatric transplant recipients acquire posttransplant lymphoproliferative disease (PTLD), and eventually 20% of those succumb to the disease. Early diagnosis of PTLD is often hampered by the unspecific symptoms and the difficult differential diagnosis, which includes atypical infections as well as graft rejection. Treatment of PTLD is limited by the high vulnerability towards antineoplastic chemotherapy in transplanted children. However, new treatment strategies and especially the introduction of the monoclonal anti-CD20 antibody rituximab have dramatically improved outcomes of PTLD. This review discusses risk factors for the development of PTLD in children, summarizes current approaches to therapy, and gives an outlook on developing new treatment modalities like targeted therapy with virus-specific T cells. Finally, monitoring strategies are evaluated.