Recurrent Epstein-Barr virus-associated post-transplant lymphoproliferative disorder: report of a patient with histologically similar but clonally distinct metachronous abdominal and brain lesions

Clinicopathologic Spectrum of Pediatric Posttransplant Lymphoproliferative Diseases Following Solid Organ Transplant

CONTEXT.—

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

OBJECTIVE.—

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

DATA SOURCES.—

Personal experiences and published works in PubMed.

CONCLUSIONS.—

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

The Global Landscape of EBV-Associated Tumors

Epstein-Barr virus (EBV), a gamma-1 herpesvirus, is carried as a life-long asymptomatic infection by the great majority of individuals in all human populations. Yet this seemingly innocent virus is aetiologically linked to two pre-malignant lymphoproliferative diseases (LPDs) and up to nine distinct human tumors; collectively these have a huge global impact, being responsible for some 200,000 new cases of cancer arising worldwide each year. EBV replicates in oral epithelium but persists as a latent infection within the B cell system and several of its diseases are indeed of B cell origin; these include B-LPD of the immunocompromised, Hodgkin Lymphoma (HL), Burkitt Lymphoma (BL), Diffuse Large B cell Lymphoma (DLBCL) and two rarer tumors associated with profound immune impairment, plasmablastic lymphoma (PBL) and primary effusion lymphoma (PEL). Surprisingly, the virus is also linked to tumors arising in other cellular niches which, rather than being essential reservoirs of virus persistence in vivo, appear to represent rare cul-de-sacs of latent infection. These non-B cell tumors include LPDs and malignant lymphomas of T or NK cells, nasopharyngeal carcinoma (NPC) and gastric carcinoma of epithelial origin, and leiomyosarcoma, a rare smooth muscle cell tumor of the immunocompromised. Here we describe the main characteristics of these tumors, their distinct epidemiologies, histological features and degrees of EBV association, then consider how their different patterns of EBV latency may reflect the alternative latency programmes through which the virus first colonizes and then persists in immunocompetent host. For each tumor, we discuss current understanding of EBV's role in the oncogenic process, the identity (where known) of host genetic and environmental factors predisposing tumor development, and the recent evidence from cancer genomics identifying somatic changes that either complement or in some cases replace the contribution of the virus. Thereafter we look for possible connections between the pathogenesis of these apparently different malignancies and point to new research areas where insights may be gained.

Molecular markers of clonality and identity in epstein-barr virus-associated B-cell lymphoproliferative disease

Epstein-Barr virus (EBV)-associated B-cell lymphoproliferative disease may be polyclonal, oligoclonal, or monoclonal. The degree of tumor clonality reflects the disease pathogenesis and may have implications for disease diagnosis, prognosis, and treatment. In this study, specimens of EBV-associated B-cell lymphoproliferative disease obtained from immunocompromised hosts were analyzed for molecular markers of cellular and virologic clonality and virologic identity. Each tumor specimen was assessed for immunoglobulin gene JH region rearrangement, the structure of the EBV genome termini, and the EBV genotype(s) present using a new EBV genotyping assay based upon LMP-1 gene sequence variation. The results of the JH rearrangement and EBV termini assays were generally concordant in their assessment of tumor specimen clonality, and both assays contributed to establishing clonal identity between different tumor specimens. The EBV genotyping assay did not significantly contribute to the assessment of tumor clonality but did established clear virologic identity between different tumor specimens obtained from the same individual. In one individual, these three assays together characterized a multi-focal, monoclonal tumor that may have arisen through clonal selection after sequential infections with two different EBV genotypes. In summary, the JH rearrangement and EBV termini assays each provided different but complementary information on tumor clonality, while the EBV genotyping assay proved most useful for establishing virologic identity among tumors. Utilization of these three assays together may provide new insight into the pathogenesis of EBV-associated B-cell lymphoproliferative disease.

Regression and clonally distinct recurrence of human immunodeficiency virus related Burkitt-like lymphoma during antiretroviral therapy

An increased incidence of intermediate to high-grade Non Hodgkin's Lymphoma is found in individuals with AIDS. Although immune function in AIDS patients can be improved through the use of antiretroviral therapy, the contribution of these drugs to lymphoma regression is not known. Here we describe the complete regression and subsequent recurrence of high grade, Burkitt-like lymphoma during antiretroviral therapy in a patient with AIDS. Antiretroviral therapy resulted in diminished viral load and modest improvement in CD4+ T cell counts. Lymphoma regressed initially, but relapsed 3 months later. Tissue taken from the initial and recurrent tumor demonstrated different clonal rearrangements. The recurrent lymphoma did not respond to continued antiretroviral therapy. In Conclusion, antiretroviral therapy may contribute to lymphoma regression in AIDS lymphoma. Clinically recurrent disease may be clonally distinct.

The diverse pathology of post-transplant lymphoproliferative disorders: the importance of a standardized approach

Post-transplant lymphoproliferative disorders (PTLD) are a diverse group of abnormal lymphoid growths that include both hyperplasias and neoplasias. They have been divided into several general pathologic categories that have prognostic significance. These include early or hyperplastic PTLD, polymorphic PTLD, and lymphomatous or monomorphic PTLD. The majority of PTLDs are of B-cell origin and contain Epstein-Barr virus (EBV). However, PTLDs of T- or NK-cell origin have been described, and late-arising EBV-negative lymphoid tumors are becoming more frequently reported in this population. Other lymphoid neoplasms, such as those arising from mucosal-associated lymphoid tissue (MALTomas), have recently been recognized in transplant patients, and their relationship to PTLD is uncertain. Multicentric PTLD may represent either advanced-stage disease or multiple independent primary tumors. Likewise, recurrent PTLD may represent true recurrence or the emergence of a second primary tumor. Transplant patients are also at risk for other opportunistic neoplasms, including EBV-associated leiomyosarcomas that may be seen alone or in conjunction with PTLD. This underscores the necessity for pathologic diagnosis of mass lesions in this patient population. The pathologist should strive to categorize the form of post-transplant lymphoproliferation in accordance with currently accepted criteria. The diagnosis should incorporate the histopathologic appearance, cell phenotype, clonal status, and EB viral status. The pathologist may play a special role in guiding therapy by ascertaining the presence of such markers as CD20 on tumor cells. Specialized techniques, such as molecular analysis of oncogenes/tumor suppressor genes and evaluation of host:donor status of PTLD, may play important roles in diagnostic evaluation in the future.