Impact of Epstein-Barr virus in monomorphic B-cell posttransplant lymphoproliferative disorders: a histogenetic study

Posttransplant Lymphoproliferative Disease Following Pancreas Transplantation: A 40 Year Single-Center Experience

BACKGROUND

Chronic immunosuppression following pancreas transplantation carries significant risk, including posttransplant lymphoproliferative disease (PTLD). We sought to define the incidence, risk factors, and long-term outcomes of PTLD following pancreas transplantation at a single center.

METHODS

All adult pancreas transplants between February 1, 1983 and December 31, 2023 at the University of Minnesota were reviewed, including pancreas transplant alone (PTA), simultaneous pancreas-kidney transplants (SPK), and pancreas after kidney transplants (PAK).

RESULTS

Among 2353 transplants, 110 cases of PTLD were identified, with an overall incidence of 4.8%. 17.3% were diagnosed within 1 year of transplant, 32.7% were diagnosed within 5 years, and 74 (67.3%) were diagnosed after 5 years. The overall 30-year incidence of PTLD did not differ by transplant type-7.4% for PTA, 14.2% for SPK, and 19.4% for PAK (p = 0.3). In multivariable analyses, older age and Epstein-Barr virus seronegativity were risk factors for PTLD, and PTLD was a risk factor for patient death. PTLD-specific mortality was 32.7%, although recipients with PTLD had similar median posttransplant survival compared to those without PTLD (14.9 year vs. 15.6 year, p = 0.9).

CONCLUSIONS

PTLD following pancreas transplantation is associated with significant mortality. Although the incidence of PTLD has decreased over time, a high index of suspicion for PTLD following PTx should remain in EBV-negative recipients.

Post-transplant lymphoproliferative disorders following kidney transplantation: A literature review with updates on risk factors, prognostic indices, screening strategies, treatment and analysis of donor type

Post-transplant lymphoproliferative disorders (PTLD) is a devastating complication of kidney transplantation with an insidious presentation and potential to disseminate aggressively. This review delineates the risk factors, prognostic indexes, screening, current management algorithm and promising treatment strategies for PTLD. Kidneys from both extended criteria donors (ECD) and living donors (LD) are being increasingly used to expand the donor pool. This review also delineates whether PTLD outcomes vary based on these donor sources. While Epstein-Barr virus (EBV) is a well-known risk factor for PTLD development, the use of T-cell depleting induction agents has been increasingly implicated in aggressive, monomorphic forms of PTLD. Research regarding maintenance therapy is sparse. The international prognostic index seems to be the most validate prognostic tool. Screening for PTLD is controversial, as annual PET-CT is most sensitive but costly, while targeted monitoring of EBV-seronegative patients was more economically feasible, is recommended by the American Society of Transplantation, but is limited to a subset of the population. Other screening strategies such as using Immunoglobulin/T-cell receptor require further validation. A risk-stratified approach is taken in the treatment of PTLD. The first step is the reduction of immunosuppressants, after which rituximab and chemotherapy may be introduced if unsuccessful. Some novel treatments have also shown potential benefit in studies: brentuximab vedotin, chimeric antigen receptor T-cell therapy and EBV-specific cytotoxic T lymphocytes. Analysis of LD v DD recipients show no significant difference in incidence and mortality of PTLD but did reveal a shortened time to development of PTLD from transplant. Analysis of SCD vs ECD recipients show a higher incidence of PTLD in the ECD group, which might be attributed to longer time on dialysis for these patients, age, and the pro-inflammatory nature of these organs. However, incidence of PTLD overall is still extremely low. Efforts should be focused on optimising recipients instead. Minimising the use of T-cell depleting therapy while encouraging research on the effect of new immunosuppressants on PTLD, screening for EBV status are essential, while enabling shared decision-making during counselling when choosing kidney donor types and individualised risk tailoring are strongly advocated.

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.

Recent Advances in Adult Post-Transplant Lymphoproliferative Disorder

PTLD is a rare but severe complication of hematopoietic or solid organ transplant recipients, with variable incidence and timing of occurrence depending on different patient-, therapy-, and transplant-related factors. The pathogenesis of PTLD is complex, with most cases of early PLTD having a strong association with Epstein-Barr virus (EBV) infection and the iatrogenic, immunosuppression-related decrease in T-cell immune surveillance. Without appropriate T-cell response, EBV-infected B cells persist and proliferate, resulting in malignant transformation. Classification is based on the histologic subtype and ranges from nondestructive hyperplasias to monoclonal aggressive lymphomas, with the most common subtype being diffuse large B-cell lymphoma-like PTLD. Management focuses on prevention of PTLD development, as well as therapy for active disease. Treatment is largely based on the histologic subtype. However, given lack of clinical trials providing evidence-based data on PLTD therapy-related outcomes, there are no specific management guidelines. In this review, we discuss the pathogenesis, histologic classification, and risk factors of PTLD. We further focus on common preventive and frontline treatment modalities, as well as describe the application of novel therapies for PLTD and elaborate on potential challenges in therapy.

A phase I/II trial of brentuximab vedotin plus rituximab as frontline therapy for patients with immunosuppression-associated CD30+ and/or EBV + lymphomas

Treatment strategies for post-transplant lymphoproliferative disorders (PTLD) consist of response-adapted risk-stratified methods using immunosuppression reduction, immunotherapy, and chemotherapy. We investigated the efficacy of Brentuximab vedotin given concurrently with Rituximab (BV + R) once weekly for four weeks, followed by optional consolidation, and up to one year of maintenance. Among 20 assessable patients, BV + R therapy resulted in an overall response rate of 75% (95% CI 51 to 91, p = 0.044) with 60% achieving a complete response. Median time to best response was 28 days. Two-year progression-free survival and overall survival rates were 75 and 90%, respectively. Most common severe grade 3/4 treatment-related toxicities included neutropenia (40%), hypertension (30%), infection (25%), and peripheral neuropathy (15%). BV + R is a novel and effective therapeutic strategy that achieved rapid and durable remissions in previously untreated PTLD patients; however, this treatment platform requires further modification due to the high rates of treatment-related toxicity.Key pointsBrentuximab vedotin + Rituximab showed ORR and CR rates of 75 and 60% in patients with immunosuppression-associated lymphoid malignanciesHigh rates of treatment delay were attributed to treatment-related toxicity; further dosing optimization of this regimen is required.

Distinctive Clinicopathologic Features of Monomorphic B-cell Post-transplant Lymphoproliferative Disorders in Children

INTRODUCTION

Post-transplant lymphoproliferative disorders (PTLDs) comprise a heterogeneous group of Epstein-Barr virus (EBV)-positive or negative lymphoid or plasmacytic lesions in solid organ or hematopoietic stem cell (HSC) transplant recipients. Although PTLDs in adults have been extensively studied, the clinicopathologic features of monomorphic B-cell PTLD in children, particularly EBV-negative forms, are still poorly understood.

METHODS

We retrospectively reviewed all our pediatric cases of monomorphic B-cell PTLDs diagnosed in the past 10 years. Clinical data were reviewed. Pathologic data including histologic types and EBV status were analyzed. Additional immunohistochemical stains, FISH studies, and TP53 gene mutational status were performed.

RESULTS

4 of 18 cases were EBV-negative. All 4 EBV-negative cases were strikingly confined to the gastrointestinal (GI) tract or abdominal lymph nodes, while tumors in EBV-positive cases were found at various anatomic sites; 2 of 4 EBV-negative cases carried mutations in TP53 gene. Our cohort also included 2 rare types of PTLD, one plasmablastic lymphoma and one high-grade B-cell lymphoma, not otherwise specified (HGBL, NOS).

CONCLUSION

We report that monomorphic B-cell PTLDs in children have distinctive clinical and pathological features. More studies are needed to clarify whether and how much these pediatric PTLDs differ from their adult counterparts.

Risk factors evaluation of post-transplant lymphoproliferative disorders after allogeneic haematopoietic stem cell transplantation with comparison between paediatric and adult

To describe the clincopathological features and evaluate risk factors of post-transplant lymphoproliferative disorder (PTLD) after allogeneic haematopoietic stem cell transplants (allo-HSCT), with comparison between paediatric and adult .Clinicopathological features of 81 cases of PTLD after allo-HSCT were analysed by histopatholgy, immunohistochemistry and in situ hybridisatioin.The cases included 58 males and 23 females with a median age of 26.7 years (range 6-55 years) and the PTLDs developed 1-60 months post-transplant (mean 5.9 months). The histological types indicated 10 cases of non-destructive PTLD, including 4 of plasmacytic hyperplasia, 5 of infectious mononucleosis and 1 of florid follicular hyperplasia. Fifty-six cases were polymorphic PTLD, and 15 were monomorphic PTLD, including thirteen of diffuse large B cell lymphoma, 1 of extranodal nasal type natural killer (NK)/T cell lymphoma and 1 of plasmablastic lymphoma. Foci and sheets of necrosis were observed in 31 cases. The infected ratio of Epstein-Barr virus (EBV) was 91.4%. Some cases were treated by reduction of immunosuppression, antiviral therapy, donor lymphocyte infusion or anti-CD20 monoclonal rituximab. Thirty-three cases died. Compared with that of adult, overall survival of paediatric recipient may be better.The first half year after allo-HSCT is very important for the development of PTLD. Type of PTLD, EBV infection and graft-versus-host disease are risk factors. The prognosis of PTLD is poor, and PTLD after allo-HSCT exhibits some features different from that after solid organ transplantation and some differences existing between adult and paediatric recipients.

Epstein-Barr Virus-negative Marginal Zone Lymphoma as an Uncommon Form of Monomorphic Posttransplant Lymphoproliferative Disorder

Monomorphic posttransplant lymphoproliferative disorders have been defined as lymphoid or plasmacytic proliferations that fulfill criteria for one of the B-cell or T/NK-cell neoplasms recognized in immunocompetent hosts in the current WHO Classification. Low-grade B-cell neoplasms have historically been excluded from this category, although rare reports of marginal zone lymphoma (MZL) have been described. We report 9 cases of posttransplant Epstein-Barr virus-negative MZL, all arising in solid organ transplant recipients (4 renal, 3 liver, 1 cardiac, and 1 liver, pancreas, and small bowel). Seven were extranodal MZL of mucosa-associated lymphoid tissue type, all of which had gastrointestinal involvement (4 colon, 1 duodenum, 1 stomach, and 1 oropharynx/base of tongue). Notably, the preferential involvement of intestine distinguishes posttransplant extranodal MZL from sporadic cases. Immunoglobulin light-chain restriction was seen in all cases, with polymerase chain reaction showing a monoclonal pattern in 7 of 8 cases with successful amplification of polymerase chain reaction products. A clonally unrelated recurrence was seen in one case. Next-generation sequencing identified recurrent mutations previously reported in MZL in 3/5 cases. MZL was diagnosed at least 1 year after solid organ transplant (median time to presentation, 84 mo; range, 13 to 108 mo). The median age was 44 (range, 9 to 73 y); the male: female ratio was 5:4. The mean follow-up was 33.4 months, with an indolent clinical course observed. A subset responded to reduction in immunosuppression and anti-CD20 therapy alone. These data support the designation of Epstein-Barr virus-negative MZL as an uncommon form of monomorphic posttransplant lymphoproliferative disorders.

Immune response in LPD during methotrexate administration (MTX-LPD) in rheumatoid arthritis patients

Methotrexate (MTX) is known as a first-line synthetic disease-modifying anti-rheumatic drug (DMARD) for the treatment of rheumatoid arthritis (RA). Although the risk of LPD development increases by RA inflammation itself, observation of spontaneous regression of LPD after MTX discontinuation lead to the theory of lymphomagenic role of MTX. In this review, we focused on the several immune response involved in LPD that developed under MTX administration in RA patients.

Post Transplant Lymphoproliferative Disorder

Posttransplant lymphoproliferative disorder is an extremely fatal complication arising in transplant recipients as a side effect of immunosuppression. PTLDs are seen after both solid organ and hematopoietic stem cell transplants though the incidence is much higher in the former. Primary Epstein-Barr virus (EBV) infection or reactivation due to a state of immune dysregulation along with intensity of immunosuppression used are of paramount importance in pathogenesis of PTLD. EBV associated PTLDs occur early in the post transplant period whereas late onset lymphomas are usually EBV negative. The uncontrolled B cell proliferation can create a spectrum of histological patterns from nondestructive lesions to destructive polymorphic or more aggressive monomorphic PTLDs. Early detection of seropositivity by serial monitoring in the recipient can prevent PTLD development by starting pre-emptive therapy. The mainstay treatment in established cases remains reduction of immunosuppression. Chemotherapeutic and immunomodulatory agents are added sequentially based on the type of PTLD and based on its response to initial therapy. Despite various treatment options available, the morbidity remains high and achieving state of disease remission without causing graft rejection can be quite challenging. Hence, a better understanding in pathobiology of EBV+ versus EBV- PTLDS may help prevent lymphomagenesis in transplant recipients.

Cellular Immunotherapy in Lymphoma: Beyond CART Cells

OPINION STATEMENT

Cellular immunotherapy has been rapidly evolving and increasingly utilized in the management of relapsed and refractory lymphoma. CD19-specific chimeric antigen receptor T cells (CARTs) have achieved impressive results in pivotal clinical trials. Although CART development continues, these products have fundamental limitations that may make them less desirable in particular settings. For example, CARTs can only target cell surface antigens and thus are incapable of targeting intracellular tumor-associated proteins. In contrast to CARTs, conventional T cell receptors (TCR) allow T cells to target any cellular antigen, including intracellular proteins, since they interact with peptides presented by MHC I and II molecules. T cells recognizing EBV antigens through native TCRs have been successfully employed for treatment and prophylaxis of EBV-associated lymphomas, including post-transplant lymphoproliferative disorder. Currently, transgenic TCR-transduced T cells targeting nonviral tumor antigens remain experimental but, if successful, could become an invaluable cellular therapy option. Because the manufacturing process of autologous T cell products, including CARTs and other tumor-specific T cells, takes several weeks, patients often need bridging therapy to maintain disease control, which may be challenging. Novel cellular platforms, such as genetically modified NK and NKT cells, may be amenable to allogeneic use and thus may allow production as a readily available, "off-the-shelf" product. As cellular therapies beyond CART continue to grow, available therapeutic options for relapsed and refractory lymphoma patients are expected to expand further.

Systematic review and meta-analysis of post-transplant lymphoproliferative disorder in lung transplant recipients

A systematic review of papers in English on post-transplant lymphoproliferative disorder (PTLD) in lung transplant recipients (LTR) using MEDLINE, EMBASE, SCOPUS, and Cochrane databases was performed. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) recommendations were strictly adhered to. Pooled odds ratios (pOR) were calculated from a random-effects model, and heterogeneity among studies was quantitated using I² values. Fourteen studies published from 2005 to 2015 were included in the meta-analysis. One hundred and sixty-four lung transplant recipients were included. LTRs who received single vs bilateral were associated with a 7.67-fold risk of death after PTLD (6 studies with 64 LTRs; pOR 7.67 95% CI 1.98-29.70; P = .003). pOR of death for early onset PTLD (<1 year post-LT) vs late onset (>1 year post-LT) was not different (3 studies with 72 LTRS; pOR 0.62, 95% CI 0.20-1.86, P = .39). Standardized mean difference (SMD) in time from transplant to PTLD onset between LTRs who died vs alive was not different (9 studies with 109 LTRs; SMD 0.03, 95% CI -0.48-0.53, P = .92). Survival in polymorphic vs monomorphic PTLD and extranodal vs nodal disease was similar (4 studies with 31 LTRs; pOR 0.44, 95% CI 0.08-2.51; P = .36. 6 studies with 81 LTRs; pOR 1.05 95% CI 0.31-3.52, P = .94). This meta-analysis demonstrates that single LTRs are at a higher risk of death vs bilateral LTRs after the development of PTLD.

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

Post-transplant lymphoproliferative disorders of T- or NK-cell origin (T/NK-PTLD) are rare entities and their genetic basis is unclear. We performed targeted sequencing of 465 cancer-related genes and high-resolution copy number analysis in 17 T-PTLD and 2 NK-PTLD cases. Overall, 377 variants were detected, with an average of 20 variants per case. Mutations of epigenetic modifier genes (TET2, KMT2C, KMT2D, DNMT3A, ARID1B, ARID2, KDM6B, n=11). and inactivation of TP53 by mutation and/or deletion(n=6) were the most frequent alterations, seen across disease subtypes, followed by mutations of JAK/STAT pathway genes (n=5). Novel variants, including mutations in TBX3 (n=3), MED12 (n=3) and MTOR (n=1), were observed as well. High-level microsatellite instability was seen in 1 of 14 (7%) cases, which had a heterozygous PMS2 mutation. Complex copy number changes were detected in 8 of 16 (50%) cases and disease subtype-specific aberrations were also identified. In contrast to B-cell PTLDs, the molecular and genomic alterations observed in T/NK-PTLD appear similar to those reported for peripheral T-cell lymphomas occurring in immunocompetent hosts, which may suggest common genetic mechanisms of lymphoma development.

Monomorphic Post-transplant Lymphoproliferative Disorder After Kidney Transplantation and Hematopoietic Stem Cell Transplantation: Clinicopathological Characteristics, Treatments and Prognostic Factors

Post-transplant lymphoproliferative disorders (PTLDs) are a heterogeneous group of lymphoid neoplasms associated with immunosuppression following transplantation. Among PTLDs, monomorphic PTLD (m-PTLD) is the largest category; however, its characteristics and survival outcome are not fully understood because of low incidence. This study enrolled 30 adult patients with m-PTLD after kidney-transplantation (KT, n = 17) and hematopoietic stem cell transplantation (HSCT, n = 13) from January 1998 to December 2014. The incidence rates of m-PTLD were 0.74 and 3.63% in the KT and HSCT groups, respectively. M-PTLD patients in the HSCT group were younger and showed earlier onset, with EBV-encoded small RNAs (EBER) more frequently identified. Diffuse large B cell lymphoma (DLBCL) was the main pathological type, and the digestive system was the most extranodal involvement site in m-PTLD after KT and HSCT. Among the 28 patients with DLBCL m-PTLD,the complete remission rate after rituximab treatment was higher than in patients not administered rituximab treatment (P = 0.038). With a median follow-up of 46 months after m-PTLD diagnosis, the estimated 5-year overall survival (OS) was 59.2 ± 9.1% in all patients, and 64.2 ± 11.8 and 52.7 ± 14.1% in the KT and HSCT groups, respectively (P = 0.741). ECOG PS, Ann Arbor stage, and CD68 IHC expression were independent prognostic factors for OS. M-PTLD is a rare but serious complication after transplantation. Ongoing efforts to standardize safe and effective treatment protocols would improve the poor overall survival. The independent prognostic factors contributed to risk-stratified treatment, and might be validated by larger studies.

EBV-negative monomorphic B-cell post-transplant lymphoproliferative disorders are pathologically distinct from EBV-positive cases and frequently contain TP53 mutations

Monomorphic post-transplant lymphoproliferative disorder commonly resembles diffuse large B-cell lymphoma or Burkitt lymphoma, and most are Epstein-Barr virus (EBV) positive. We retrospectively identified 32 cases of monomorphic post-transplant lymphoproliferative disorder from two institutions and evaluated EBV in situ hybridization; TP53 mutation status; p53, CD30, myc, and BCL2 expression by immunohistochemistry; proliferation index by Ki67; and germinal center vs non-germinal center immunophenotype by Hans criteria. Post-transplant lymphoproliferative disorder arose after hematopoietic stem cell transplant in five and solid organ transplant in 27 patients, a median of 4 and 96 months after transplant, respectively (overall median latency 71 months, range 2-295). The most common morphology was diffuse large B-cell lymphoma (28 cases), with three cases of Burkitt lymphoma, and one case of plasmablastic lymphoma. Ten cases (31%) were EBV negative. Of those with the morphology of diffuse large B-cell lymphoma, the EBV-negative cases were more frequently TP53-mutated (P<0.001), p53 positive by immunohistochemistry (P<0.001), CD30 negative (P<0.01), and of germinal center immunophenotype (P=0.01) compared with EBV-positive cases. No statistically significant difference in overall survival was identified based on EBV, TP53 mutation status, germinal center vs non-germinal center immunophenotype, or other immunohistochemical parameters evaluated. Patients who died of post-transplant lymphoproliferative disorder were older with a longer latency from time of transplant to diagnosis (P<0.05). Our study demonstrates that diffuse large B-cell lymphoma-related immunohistochemical prognostic markers have limited relevance in the post-transplant setting and underscores differences between EBV-positive and EBV-negative post-transplant lymphoproliferative disorder in terms of immunophenotype and TP53 mutation frequency, supporting an alternative pathogenesis for EBV-negative post-transplant lymphoproliferative disorder.

Matched-pair analysis: identification of factors with independent influence on the development of PTLD after kidney or liver transplantation

BACKGROUND

Post-transplant lymphoproliferative disorder (PTLD) adversely affects patients' long-term outcome.

METHODS

The paired t test and McNemar's test were applied in a retrospective 1:1 matched-pair analysis including 36 patients with PTLD and 36 patients without PTLD after kidney or liver transplantation. Matching criteria were age, gender, indication, type of transplantation, and duration of follow-up. All investigated PTLD specimen were histologically positive for EBV. Risk-adjusted multivariable regression analysis was used to identify independence of risk factors for PTLD detected in matched-pair analysis. The resultant prognostic model was assessed with ROC-curve analysis.

RESULTS

Patients suffering with PTLD had shorter mean survival (p = 0.004), more episodes of CMV infections or reactivations (p = 0.042), and fewer recipient HLA A2 haplotypes (p = 0.007), a tacrolimus-based immunosuppressive regimen (p = 0.052) and higher dosages of tacrolimus at hospital discharge (Tac dosage) (p = 0.052). Significant independent risk factors for PTLD were recipient HLA A2 (OR = 0.07, 95 % CI = 0.01-0.55, p = 0.011), higher Tac dosages (OR = 1.29, 95 % CI = 1.01-1.64, p = 0.040), and higher numbers of graft rejection episodes (OR = 0.38, 95 % CI = 0.17-0.87, p = 0.023). The following prognostic model for the prediction of PTLD demonstrated good model fit and a large area under the ROC curve (0.823): PTLD probability in % = Exp(y)/(1 + Exp(y)) with y = 0.671 - 1.096 × HLA A2-positive recipient + 0.151 × Tac dosage - 0.805 × number of graft rejection episodes.

CONCLUSIONS

This study suggests prognostic relevance for recipient HLA A2, CMV, and EBV infections or reactivations and strong initial tacrolimus-based immunosuppression. Patients with risk factors may benefit from intensified screening for PTLD.

Secondary Malignant Neoplasms Following Haematopoietic Stem Cell Transplantation in Childhood

Improving survival rates in children with malignancy have been achieved at the cost of a high frequency of late adverse effects of treatment, especially in intensively treated patients such as those undergoing haematopoietic stem cell transplantation (HSCT), many of whom suffer the high burden of chronic toxicity. Secondary malignant neoplasms (SMNs) are one of the most devastating late effects, cause much morbidity and are the most frequent cause of late (yet still premature) treatment-related mortality. They occur in up to 7% of HSCT recipients by 20 years post-HSCT, and with no evidence yet of a plateau in incidence with longer follow-up. This review describes the epidemiology, pathogenesis, clinical features and risk factors of the three main categories of post-HSCT SMNs. A wide range of solid SMNs has been described, usually occurring 10 years or more post-HSCT, related most often to previous or conditioning radiotherapy. Therapy-related acute myeloid leukaemia/myelodysplasia occurs earlier, typically three to seven years post-HSCT, mainly in recipients of autologous transplant and is related to previous alkylating agent or topoisomerase II inhibitor chemotherapy. Post-transplant lymphoproliferative disorders occur early (usually within two years) post-HSCT, usually presenting as Epstein-Barr virus-related B cell non-Hodgkin lymphoma.

Occurrence and prognostic relevance of CD30 expression in post-transplant lymphoproliferative disorders

Post-transplant lymphoproliferative disorders (PTLDs) are potentially fatal, often Epstein-Barr virus (EBV)-driven neoplasias developing in immunocompromised hosts. Initial treatment usually consists of a reduction in immunosuppressive therapy and/or rituximab with or without chemotherapy. However, patients who relapse do poorly, and new treatment options are warranted. With the introduction of the immunoconjugate brentuximab vedotin, the CD30 antigen has become an effectively targetable molecule. Therefore, we investigated the frequency and level of CD30 expression in PTLDs. We identified 108 patients with PTLDs diagnosed during 1994-2011, of whom 62 had adequate paraffin-embedded tissue for tissue microarray construction. Immunohistochemical expression of CD30 was consistently detected in all types of PTLD (overall 85.25%), including the monomorphic subtypes, and was correlated with a more favorable outcome. For diffuse large B-cell lymphoma (DLBCL)-type PTLD this was regardless of EBV status, and remained significant in multivariate analysis. Cell-of-origin had no independent prognostic value in our series of DLBCL PTLD.

Post-transplant lymphoproliferative disorders are not associated with IgG4 sclerosing disease

BACKGROUND

Although the majority of post-transplant lymphoproliferative disorder (PTLD) cases are associated with Epstein-Barr virus (EBV), 20-42% of cases are EBV negative (EBV-N). The antigenic stimulus that drives EBV-N PTLD is unknown, but is likely heterogeneous. A common feature of PTLD, regardless of EBV status, is an abnormal polytypic lymphoplasmacytic infiltrate. Immunglobulin-G4 (IgG4) syndrome is also characterized by a polytypic lymphoplasmacytic infiltrate with a predominance of IgG4-positive (IgG4-P) plasma cells.

METHODS

We investigated the possibility of an association between EBV-N PTLD and IgG4 syndrome. Of 33 evaluated PTLD cases, 9 (27%) were EBV-N. EBV-N PTLD cases showed longer transplantation-to-diagnosis times than EBV-positive cases.

RESULTS

A single patient had a preceding benign duodenal biopsy with focally prominent IgG4-P plasma cells; however, no clinical data supported IgG4 syndrome, precluding an association between IgG4 syndrome and subsequent EBV-N PTLD in this patient.

CONCLUSION

As none of 29 evaluable cases of PTLD (including all 9 EBV-N cases) were associated with an increase in IgG4-P plasma cells, IgG4 syndrome does not appear to play a role in the etiology of EBV-N PTLD. The significance of these findings and the current understanding of the etiology of EBV-N PTLD are discussed.

A population-based study of 135 lymphomas after solid organ transplantation: The role of Epstein-Barr virus, hepatitis C and diffuse large B-cell lymphoma subtype in clinical presentation and survival

BACKGROUND

Epstein-Barr virus (EBV) plays a major role in the development of post-transplant lymphoproliferative disorder (PTLD), but there is an increasing awareness of EBV-negative PTLD. The clinical presentation of EBV-negative PTLD has not been as well characterised as EBV-positive cases. Further, there is limited knowledge on the clinical importance of diffuse large B-cell lymphoma (DLBCL) cell of origin subtype post-transplant.

MATERIALS AND METHODS

We studied the role of EBV, hepatitis C (HCV) and DLBCL subtype in clinical presentation and survival in 135 post-transplant lymphomas diagnosed 1980-2006 in a population-based cohort of 10 010 Swedish solid organ transplant recipients. The lymphomas were re-evaluated according to WHO 2008, examined for EBV, and clinical data were collected from medical records.

RESULTS

Lymphoma incidence rate was 159/100 000 person-years and is also reported by lymphoma subtype. EBV-negative lymphomas constituted 48% and were associated with HCV infection (p = 0.02), bone marrow involvement (p < 0.001), and T-cell phenotype (p = 0.002). Among DLBCL, 78% were of non-germinal centre subtype, which was associated with EBV-positivity (69%, p = 0.001), early occurrence (p = 0.03), heart/liver/lung/pancreas recipients (p = 0.02), anti-T-cell globulin (p = 0.001), and tacrolimus treatment (p = 0.02). DLBCL subtypes had similar overall survival. Five-year overall survival was 42% in all treated patients. Independent poor prognostic factors were older age, B symptoms, ECOG 2-4, kidney/pancreas/heart recipients, T-cell lymphoma, and HCV-infection.

CONCLUSIONS

With long follow-up, a large part of PTLD is EBV-negative, due to a high proportion of T-cell lymphomas and low of polymorphic PTLD. EBV-negative PTLD have a different clinical presentation. HCV may play an aetiological role in late-onset PTLD and was revealed as a new prognostic factor for inferior survival that needs to be confirmed in larger studies. The heavier immunosuppression in non-kidney transplantations seems to play a role in the development of non-germinal centre DLBCL. DLBCL cell of origin subtype lacks prognostic importance in the transplant setting.

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).

Epstein-barr virus-negative post-transplant lymphoproliferative diseases: three distinct cases from a single center

Three cases of Epstein-Barr virus (EBV)-negative post-transplant lymphoproliferative disease that occurred 6 to 8 years after renal transplantation are reported. The patients respectively had gastric mucosa-associated lymphoid tissue lymphoma, gastric diffuse large B-cell lymphoma, and atypical Burkitt lymphoma. Absence of EBV in the tissue samples was demonstrated by both in situ hybridization for EBV early RNA and polymerase chain reaction for EBV DNA. Patients were treated with reduction in immunosuppression and combined chemotherapy plus an anti-CD20 monoclonal antibody, rituximab. Despite the reduction in immunosuppression, patients had stable renal functions without loss of graft functions. The patient with atypical Burkitt lymphoma had an abnormal karyotype, did not respond to treatment completely, and died due to disease progression. The other patients are still alive and in remission 5 and 3 years after diagnosis, respectively. EBV-negative post-transplant lymphoproliferative diseases are usually late-onset and are reported to have poor prognosis. Thus, reduction in immunosuppression is usually not sufficient for treatment and more aggressive approaches like rituximab with combined chemotherapy are required.

Clinicopathologic features of post-transplant lymphoproliferative disorders arising after pediatric small bowel transplant

Few studies examined the clinicopathologic features of PTLD arising in pediatric SBT patients. Particularly, the association between ATG and PTLD in this population has not been described. Retrospective review of 81 pediatric patient charts with SBT--isolated or in combination with other organs--showed a PTLD incidence of 11%, occurring more frequently in females (median age of four yr) and with clinically advanced disease. Monomorphic PTLD was the most common histological subtype. There was a significant difference in the use of ATG between patients who developed PTLD and those who did not (p < 0.01); a similar difference was seen with the use of sirolimus (p < 0.001). These results suggested a link between the combination of ATG and sirolimus and development of more clinically and histologically advanced PTLD; however, the risk of ATG by itself was not clear. EBV viral loads were higher in patients with PTLD, and median time between detection of EBV to PTLD diagnosis was three months. However, viral loads at the time of PTLD diagnosis were most often lower than at EBV detection, thereby raising questions on the correlation between decreasing viral genomes and risk of PTLD.

Molecular pathogenesis of B-cell posttransplant lymphoproliferative disorder: what do we know so far?

Posttransplant lymphoproliferative disorder (PTLD) is a potentially fatal disease that arises in 2%-10% of solid organ and hematopoietic stem cell transplants and is most frequently of B-cell origin. This very heterogeneous disorder ranges from benign lymphoproliferations to malignant lymphomas, and despite the clear association with Epstein-Barr Virus (EBV) infection, its etiology is still obscure. Although a number of risk factors have been identified (EBV serostatus, graft type, and immunosuppressive regimen), it is currently not possible to predict which transplant patient will eventually develop PTLD. Genetic studies have linked translocations (involving C-MYC, IGH, BCL-2), various copy number variations, DNA mutations (PIM1, PAX5, C-MYC, RhoH/TTF), and polymorphisms in both the host (IFN-gamma, IL-10, TGF-beta, HLA) and the EBV genome to B-cell PTLD development. Furthermore, the tumor microenvironment seems to play an important role in the course of disease representing a local niche that can allow antitumor immune responses even in an immunocompromised host. Taken together, B-cell PTLD pathogenesis is very complex due to the interplay of many different (patient-dependent) factors and requires thorough molecular analysis for the development of novel tailored therapies. This review aims at giving a global overview of the currently known parameters that contribute to the development of B-cell PTLD.

Plasmablastic lymphoma following transplantation

Posttransplant lymphoproliferative disorder is a serious complication following solid organ as well as hematopoietic stem cell transplantation due to prolonged immunosuppressive therapy. Plasmablastic lymphoma, although classically associated with HIV infection, has since been described in transplant patients as a variant of posttransplant lymphoproliferative disorder with varying clinical presentations. Here we add two additional cases to the literature: one following lung transplantation and one following pancreatic transplantation. In addition, the demographic, therapeutic, and immunophenotypic characteristics from prior reported cases are summarized.

Early onset, EBV− PTLD in pediatric liver-small bowel transplantation recipients: a spectrum of plasma cell neoplasms with favorable prognosis

Five cases of EBV− PTLD in pediatric recipients of combined liver and small bowel allografts are reported. The lesions were plasma cell neoplasms that resolved completely after minimal treatment.

Post transplant lymphoproliferative disorders: risk, classification, and therapeutic recommendations

OPINION STATEMENT

Post transplant lymphoproliferative disorder (PTLD) is a heterogeneous disease that may occur in recipients of solid organ transplants (SOT) and hematopoietic stem cell transplant. The risk of lymphoma is increased 20-120% compared with the general population with risk dependent in part on level of immune suppression. In addition, recent data have emerged, including HLA and cytokine gene polymorphisms, regarding genetic susceptibility to PTLD. Based on morphologic, immunophenotypic, and molecular criteria, PLTD are classified into 4 pathologic categories: early lesions, polymorphic, monomorphic, and classical Hodgkin lymphoma. Evaluation by expert hematopathology is critical in establishing the diagnosis. The aim of therapy for most patients is cure with the concurrent goal of preservation of allograft function. Given the pathologic and clinical heterogeneity of PTLD, treatment is often individualized. A mainstay of therapy remains reduction of immune suppression (RI) with the level of reduction being dependent on several factors (e.g., history of rejection, current dosing, and type of allograft). Outside of early lesions and/or low tumor burden, however, RI alone is associated with cure in a minority of subjects. We approach most newly-diagnosed polymorphic and monomorphic PTLDs similarly using frontline single-agent rituximab (4 weeks followed by abbreviated maintenance) in conjunction with RI. Frontline combination chemotherapy may be warranted for patients with high tumor burden in need of prompt response or following failure of RI and/or rituximab. Due to chemotherapy-related complications in PTLD, especially infectious, we advocate comprehensive supportive care measures. Surgery or radiation may be considered for select patients with early-stage disease. For PTLD subjects with primary CNS lymphoma, we utilize therapeutic paradigms similar to immunocompetent CNS lymphoma using high-dose methotrexate-based therapy with concurrent rituximab therapy and sequential high-dose cytarabine. Finally, novel therapeutic strategies, especially adoptive immunotherapy, should continued to be explored.

Extranodal NK/T-cell lymphoma, nasal type, includes cases of natural killer cell and αβ, γδ, and αβ/γδ T-cell origin: a comprehensive clinicopathologic and phenotypic study

Extranodal NK/T-cell lymphoma (ENKTL), nasal type, may be of NK or T-cell origin; however, the proportion of T-ENKTLs and whether they are of αβ or γδ type remains uncertain. To elucidate the cell of origin and detailed phenotype of ENKTL and assess any clinicopathologic associations, 67 cases of ENKTL from Thailand were investigated, together with 5 γδ enteropathy-associated T-cell lymphomas (EATLs) for comparison. In all, 70% of the ENKTL were T-cell receptor (TCR) β,γ and, in cases tested, δ negative (presumptive NK origin); 5% were TCR γδ, 3% were TCR αβ, 1% were TCR αβ/γδ, and 21% were indeterminate. Out of 17 presumptive NK-ENKTLs tested, 3 had clonal TCR rearrangements. All cases were EBV and TIA-1; >85% were positive for CD3, CD2, granzyme B, pSTAT3, and Lsk/MATK; and all were CD16. Presumptive NK-ENKTLs had significantly more frequent CD56 (83% vs. 33%) and CXCL13 (59% vs. 0%) but less frequent PD-1 (0% vs. 40%) compared with T-ENKTLs. Of the NK-ENKTLs, 38% were Oct-2 compared with 0% of T-ENKTLs, and 54% were IRF4/MUM1 compared with 20% of T-ENKTLs. Only αβ T-ENKTLs were CD5. Intestinal ENKTLs were EBV and had significantly more frequent CD30, pSTAT3, and IRF4/MUM1 expression but less frequent CD16 compared with γδ EATL. Significant adverse prognostic indicators included a primary non-upper aerodigestive tract site, high stage, bone marrow involvement, International Prognostic Index ≥2, lack of radiotherapy, Ki67 >40%, and CD25 expression. The upper aerodigestive tract ENKTLs of T-cell origin compared with those of presumptive NK origin showed a trend for better survival. Thus, at least 11% of evaluable ENKTLs are of T-cell origin. Although T-ENKTLs have phenotypic and some possible clinical differences, they share many similarities with ENKTLs that lack TCR expression and are distinct from intestinal γδ EATL.

Posttransplant lymphoproliferative disorders

Posttransplant lymphoproliferative disorders (PTLDs) are a group of diseases that range from benign polyclonal to malignant monoclonal lymphoid proliferations. They arise secondary to treatment with immunosuppressive drugs given to prevent transplant rejection. Three main pathologic subsets/stages of evolution are recognised: early, polymorphic, and monomorphic lesions. The pathogenesis of PTLDs seems to be multifactorial. Among possible infective aetiologies, the role of EBV has been studied in depth, and the virus is thought to play a central role in driving the proliferation of EBV-infected B cells that leads to subsequent development of the lymphoproliferative disorder. It is apparent, however, that EBV is not solely responsible for the “neoplastic” state. Accumulated genetic alterations of oncogenes and tumour suppressor genes (deletions, mutations, rearrangements, and amplifications) and epigenetic changes (aberrant hypermethylation) that involve tumour suppressor genes are integral to the pathogenesis. Antigenic stimulation also plays an evident role in the pathogenesis of PTLDs. Plasmacytoid dendritic cells (PDCs) that are critical to fight viral infections have been thought to play a pathogenetically relevant role in PTLDs. Furthermore, regulatory T cells (Treg cells), which are modulators of immune reactions once incited, seem to have an important role in PTLDs where antigenic stimulation is key for the pathogenesis.

p52 Activation in monomorphic B-cell posttransplant lymphoproliferative disorder/diffuse large B-cell lymphoma without BAFF-R expression

Posttransplantation lymphoproliferative disorders (PTLD) are associated with Epstein-Barr virus (EBV) and activate the NF-κB pathway. B-cell activating factor (BAFF) modulates cell growth and survival in non-Hodgkin's lymphomas. However, there are few studies of EBV, BAFF/BAFF-R signaling, and NF-κB1 and NF-κB2 pathway activation in PTLD. Diffuse large B-cell lymphomas (DLBCL) in two different clinical contexts, immunocompetent patients (DLBCL/IC; n = 30) or posttransplantation solid-organ recipients (DLBCL/PTLD; n = 21), were characterized histogenically as germinal center (GC) or non-germinal center (NGC). Expression of BAFF, BAFF-R, and NF-κB proteins p50 and p52 and the presence or absence of EBV were compared in these clinical contexts. Regardless of the GC or NGC pattern of DLBCL, BAFF-R was expressed in 37% of DLBCL/IC but in only 4.8% of DLBCL/PTLD. p52 was expressed in DLBCL/PTLD/NGC (12 of 19 cases) as compared with DLBCL/IC/NGC (0 of 18 cases). This pattern might be related to the presence of EBV and latent membrane protein 1 because p52 expression was observed primarily in EBV-positive DLBCL/PTLD cases expressing latent membrane protein 1. Thus, the activation profile or NGC pattern of DLBCL/PTLD was not associated with BAFF/BAFF-R expression, whereas nuclear p52 related to NF-κB2 pathway activation might be linked to EBV.

Post-transplant Burkitt lymphoma is a more aggressive and distinct form of post-transplant lymphoproliferative disorder

BACKGROUND

Although the literature reports a low incidence of Burkitt lymphoma (BL) as a post-transplant lymphoproliferative disorder (PTLD), this entity appears to be different from other monomorphic PTLDs (M-PTLDs), both in its aggressive clinical presentation and its distinct pathologic profile.

METHODS

Patients with BL, diagnosed in the post-transplant setting, (patients aged ≤ 18 years) were retrieved from the pathology archives at Children's Hospital of Pittsburgh of the University of Pittsburgh Medical Center from 1982 to 2010. Clinical outcomes were obtained along with pathologic review.

RESULTS

Twelve patients with pediatric BL in the post-transplant setting (9 boys, 3 girls) were retrieved. The patients displayed a monomorphic population of small to intermediate-sized, noncleaved, lymphoid elements with a "starry-sky" pattern. The immunophenotype for patients available to the study was CD20+ (n = 9/10), CD10+ (n = 8/8), bcl-6+ (n = 11/11), with a near 100% Ki-67/MIB-1 proliferation index (n = 7/7), and negative for TdT (n = 7/7). Most pretransplant Epstein-Barr virus titers were negative (n = 8/10), with post-transplant titers positive in all tested patients (n = 11), and with positive Epstein-Barr-encoded RNA in situ hybridization in most cases (n = 9/11). The median time from transplantation to diagnosis was 52 months (range, 6-107 months). Nine patients were currently alive after immediate antineoplastic chemotherapy, with median disease-free time of 93 months from diagnosis (range, 2-199 months).

CONCLUSIONS

BL-PTLD had a higher Epstein-Barr virus incidence compared with sporadic and immunodeficiency-associated BL and represented a distinct monomorphic PTLD. Although some M-PTLDs can be managed less aggressively with decreased immunosuppression alone, immediate lymphoma-specific chemotherapy was associated with a favorable outcome and was strongly recommended.

Post-transplantation lymphoproliferative disorders: diagnosis, prognosis, and current approaches to therapy

Post-transplantation lymphoproliferative disorders (PTLD) are a heterogenous group of abnormal lymphoid proliferations that occur after solid organ transplant (SOT) or hematopoietic transplantation. PTLDs consist of a disease spectrum ranging from hyperplasia to aggressive lymphomas with 60-70% being Epstein-Barr virus positive. The majority of cases are B-cell, although 10-15% are of T-cell origin or rarely Hodgkin lymphoma. Recent SOT series suggest PTLD occurs at a median of 36-40 months after transplant. Clinically, extra-nodal disease is common (up to 75-85%) including CNS involvement, which is seen in 10-15% of all cases. Since the first report over 40 years ago, PTLD has remained one of the most morbid complications associated with SOT. However, recent data suggests improved survival in the modern era, especially with the integration of early rituximab-based therapy. These studies utilized first line rituximab (+/- chemotherapy) together with reduced immune suppression (RI) for monomorphic and polymorphic PTLD. It will be critical in future studies to determine which PTLDs are most amenable to initial therapy with RI alone, versus RI/rituximab, versus RI/rituximab/chemotherapy. Additionally, novel therapeutics, such as adoptive immunotherapy, should continue to be explored.

CD20 expression predicts survival in paediatric post-transplant lymphoproliferative disease (PTLD) following solid organ transplantation

The prognostic role of CD20 expression and Epstein-Barr virus (EBV) positivity in post-transplant lymphoproliferative disease (PTLD) after solid organ transplantation (SOT) in paediatric patients is poorly understood. We retrospectively examined the relationship of CD20 and EBV with the time interval from SOT to PTLD diagnosis, and PTLD-related event-free (EFS) and overall survival (OS) in 45 consecutive PTLD patients (≤25 years) following SOT. These 45 paediatric SOT patients (28 heart, 11 liver, six kidney) were diagnosed with PTLD 45 months (mean; SD 43; range 4-153; median 24·5) after SOT, with PTLD diagnosis at 118 months (mean) (SD 77; range 14-287) of age. Of 40 evaluable tumours (11 monomorphic, 19 polymorphic, five early lesions, five rare subtypes), 32 (80%) had detectable EBV and 28 (70%) were classified as CD20(+) . Patients whose PTLD expressed CD20 or EBV had shorter intervals between SOT and PTLD onset (28 vs. 64 or 77 months for CD20 and EBV respectively) (P < 0·02), even after adjusting for age at SOT. Patients with CD20(+) tumours had higher 5-year PTLD-related EFS (83·7% vs. 28·6%, P < 0·001) and OS (95·8% vs. 56·3%, P = 0·01). EBV expression was unrelated to PTLD-related EFS or OS. CD20 expression is associated with timing of development of PTLD and predicts survival in PTLD diagnosed following paediatric SOT.

Post-transplant lymphoproliferative disorder in view of the new WHO classification: a more rational approach to a protean disease?

Post-transplant lymphoproliferative disorders (PTLDs) are serious, life-threatening complications of solid-organ transplantation (SOT) and bone marrow transplantation leading to a high mortality (30-60%). PTLD represents a heterogeneous group of lymphoproliferative diseases. They become clinically relevant because of the expansion of transplantation medicine together with the development of potent immunosuppressive drugs. Although the diagnostic morphological criteria of different forms of PTLD are commonly known, rapid and correct diagnosis is not always easy. Because of the limited number of clinical trials, a consensus is lacking on the optimal treatment of PTLD. This review focuses on incidence, risk factors, clinical picture of the disease and diagnostic tools including histopathology relating to the new classification introduced in 2008 by the World Health Organisation (WHO) and treatment of PTLD.

Diagnosis in Pediatric Transplant Biopsies

Infant recipients have better survival after solid organ transplantation than older children and adults possibly due to immune tolerance. Over the past two decades, postsurgical complications have markedly decreased, and multidrug immunosuppressive regimens have become effective in preventing and treating rejection. Immunocompromised for life, these patients are susceptible to both the usual bacterial as well as opportunistic infections that often involve the lung. Post-transplant lymphoproliferative disease seems to be decreasing even further in frequency. This article focuses on the findings seen on biopsy, usually of the transplanted organ, and also of other sites affected by post-transplant complications.

Gene expression profiling of Epstein-Barr virus-positive and -negative monomorphic B-cell posttransplant lymphoproliferative disorders

Although most posttransplant lymphoproliferative disorders (PTLD) are related to Epstein-Barr virus (EBV) infection, approximately 20% lack detectable EBV (EBV-). It is uncertain whether the latter cases are truly distinct from EBV+ PTLD or possibly relate to another infectious agent. This study used gene expression profiling to further investigate the relationship between EBV+ and EBV- monomorphic B-cell PTLD, and to search for clues to their pathogenesis. Affymetrix HU133A GeneChips were used to compare 4 EBV+ and 4 EBV- cases of monomorphic B-cell PTLD. Hierarchical clustering successfully distinguished the EBV+ and EBV- groups. Relative to EBV- PTLD, 54 transcripts were over-expressed in EBV+ PTLD. The transcripts identified included IRF7 (a known regulator of EBV LMP1 expression), EBI2 (EBV-induced gene 2), and 3 that are interferon induced (MX1, IFITM1, and IFITM3). In addition, the EBV+ group contained 232 transcripts decreased relative to the EBV- group, including changes concordant with those previously reported after EBV infection of cultured B-cell lines. In summary, in a small group of monomorphic B-cell PTLD, EBV+ cases demonstrated a subset of gene expression changes associated with EBV infection of B cells. By contrast, EBV- PTLD lacked viral-associated changes suggesting that they are biologically distinct.

T-cell and NK-cell posttransplantation lymphoproliferative disorders

Posttransplantation lymphoproliferative disorders (PTLDs) of T-cell or natural killer (NK)-cell origin are an uncommon heterogeneous group of lymphoid proliferations that fulfill the criteria for one of the T- or NK-cell lymphomas/leukemias. This report summarizes 130 T/NK-cell PTLDs reported in the literature or presented at the Society for Hematopathology/European Association for Haematopathology Workshop on T/NK-cell malignancies. The T/NK-cell PTLDs occur at a median of 66 months following transplantation and are usually extranodal. The most common types reported are peripheral T-cell lymphoma, unspecified, and hepatosplenic T-cell lymphoma. Approximately one third are Epstein-Barr virus (EBV)+. The median survival is 6 months. EBV+ cases have a significantly longer survival than EBV- cases, even when indolent T-cell large granular lymphocytic leukemias are included among the EBV- cases. Many T/NK-cell PTLDs have been treated with chemotherapy, often together with decreased immunosuppression, but there are infrequent patients who have done well without chemotherapy or radiation.