Expression of EBV latent antigens, mammalian target of rapamycin, and tumor suppression genes in EBV-positive smooth muscle tumors: clinical and therapeutic implications

Intracranial malignant myopericytoma: case report and literature review

Malignant myopericytoma is an exceedingly rare soft tissue tumour with only 14 documented cases in the scientific literature. Myopericytomas can occur in association with HIV-AIDS and have a predilection for internal organs such as the bronchus, larynx, liver and brain. Ebstein-Barr virus encoded small RNA(EBER) was positive in three out of 14 cases. In this case report we present the second documented case of a malignant myopericytoma, with a positive EBER found intracranially - specifically in the supratentorial compartment - invading the superior sagittal sinus. Gross total excision of the tumour was achieved, and the patient responded well with no recurrence with only highly active antiretroviral therapy (HAART). No chemotherapy or radiotherapy has been necessary.

Epstein-Barr Virus-Positive Leiomyosarcoma in Immunocompetent Patients

OBJECTIVE

Epstein-Barr Virus-Associated Smooth Muscle Tumor (EBV-SMT) is a rare tumor with a higher rate of occurrence in unusual locations in the setting of immunodeficiency. In this study, we evaluated a cohort of ordinary leiomyosarcomas (LMS) for the presence of EBV and described the clinicopathological features deviating from routinely diagnosed cases of EBV-SMT.

MATERIAL AND METHOD

The sections of tissue microarrays including 93 classical LMS occurring in various locations were hybridized with EBER and stained for LMP1 antibody using the Leica Bond Autostainer. EBV real-time PCR assay was performed in 2 EBER-positive cases.

RESULTS

Among the 93 LMS cases, 2 non-uterine cases (2.2%) were positive for EBER and negative for LMP1, and were referred to as `EBV-positive LMS`. Both were females in their 6th decade without immunosuppression. EBV real-time PCR assay revealed the presence of EBV in one of the cases. Tumors were located in the pancreas and chest wall. Morphologically, tumors were rather myxoid, multinodular, and composed of long fascicles of spindle cells with intermediate- to high-grade features. High mitotic activity and focal necrosis were present, whereas no accompanying lymphocytes were detected. One of the patients developed metastatic disease after 3 years.

CONCLUSION

EBV-positive LMS occurring in immunocompetent patients has features distinct from classical EBV-SMT seen in immunosuppressed patients.

Clinicopathologic and Molecular Characteristics of Epstein-Barr Virus-Associated Smooth Muscle Tumor Compared With Those of Leiomyoma and Leiomyosarcoma

Epstein-Barr virus (EBV)-associated smooth muscle tumors (EBV-SMTs) are rare smooth muscle neoplasms exclusively associated with immunosuppression, such as in patients with HIV/AIDS, posttransplant, and congenital immunodeficiency. However, the genomic landscape of EBV-SMTs is poorly understood. Leiomyosarcomas harbor genomic instability and multiple recurrent DNA copy number alterations, whereas leiomyomas lack such changes. Thus, this study aimed to fill this knowledge gap by characterizing copy number alterations in EBV-SMTs and correlating this information with clinicopathologic characteristics. Our study investigated and compared the pathologic characteristics and copy number profiles of 9 EBV-SMTs (from 7 post-transplant and AIDS patients), 6 leiomyomas, and 7 leiomyosarcomas, using chromosomal microarray platforms. Our results showed a lower copy number alteration burden in EBV-SMTs and leiomyoma than in leiomyosarcoma. This contrast in the molecular profile between EBV-SMTs and leiomyosarcoma is concordant with the different clinical behaviors and pathologic characteristics exhibited by these tumors. Despite having an overall copy number alteration profile closer to leiomyoma, recurrent copy number gain of oncogenes, such as RUNX1, CCND2, and ETS2, was found in EBV-SMTs. Epigenetic alterations may play an important role in tumorigenesis as recurrent copy number gains were found in histone deacetylases. A gene enrichment analysis also demonstrated enrichment of genes involved in the host response to viral infection, suggesting that the tumor immune microenvironment may play an important role in EBV-SMT tumorigenesis.

Comprehensive Profiling of EBV Gene Expression and Promoter Methylation Reveals Latency II Viral Infection and Sporadic Abortive Lytic Activation in Peripheral T-Cell Lymphomas

Epstein-Barr virus (EBV) latency patterns are well defined in EBV-associated epithelial, NK/T-cell, and B-cell malignancies, with links between latency stage and tumorigenesis deciphered in various studies. In vitro studies suggest that the oncogenic activity of EBV in T-cells might be somewhat different from that in EBV-tropic B lymphoid cells, prompting us to study this much less investigated viral gene expression pattern and its regulation in nine EBV+ peripheral T-cell lymphoma (PTCL) biopsies. Using frozen specimens, RT-PCR showed 6/7 cases with a latency II pattern of EBV gene expression. Analyses of EBNA1 promoter usage and CpG methylation status in these six cases showed that only Qp was used, while Cp, Wp, and Fp were all silent. However, the remaining case showed an exceptionally unique latency III type with lytic activation, as evidenced by EBV lytic clonality and confirmed by the full usage of Cp and Qp as well as weakly lytic Fp and Wp, fully unmethylated Cp and marginally unmethylated Wp. Further immunostaining of the eight cases revealed a few focally clustered LMP1+ cells in 7/8 cases, with rare isolated LMP1+ cells detected in another case. Double immunostaining confirmed that the LMP1+ cells were of the T-cell phenotype (CD3+). In 6/8 cases, sporadically scattered Zta+ cells were detected. Double staining of EBER-ISH with T-cell (CD45RO/UCHL1) or B-cell (CD20) markers confirmed that the vast majority of EBER+ cells were of the T-cell phenotype. Predominant type-A EBV variant and LMP1 30-bp deletion variant were present, with both F and f variants detected. In summary, the EBV gene expression pattern in PTCL was found to be mainly of latency II (BART+EBNA1(Qp)+LMP1+LMP2A+BZLF1+), similar to that previously reported in EBV-infected nasopharyngeal epithelial, NK/T-cell, and Hodgkin malignancies; however, fully lytic infection could also be detected in occasional cases. Rare cells with sporadic immediate-early gene expression were commonly detected in PTCL. These findings have implications for the future development of EBV-targeting therapeutics for this cancer.

Clinical Course of a Rare Epstein-Barr Virus-Associated Smooth Muscle Tumor and Its Genomic Analysis

Epstein-Barr virus (EBV) can rarely induce smooth muscle tumors (SMTs). A 20-year-old female patient underwent kidney transplantation for renal failure. Since then, she has been treated with immunosuppressants, including a calcineurin inhibitor, tacrolimus, and prednisolone, owing to the immunological rejection. Three years later, she developed large liver tumors (diameter >5 cm) and multiple small lung tumors that were identified as EBV-SMTs based on the results of liver biopsy/histopathology. No intervention was performed except for the addition of a mammalian target of the rapamycin inhibitor, everolimus, which inhibits both immune reaction and SMT growth. Finally, after 8 years, the transplanted kidney became nonfunctional, and immunosuppressant administration became unnecessary as urinary dialysis was started. Under these circumstances, SMT growth was observed despite the absence of immunosuppressant administration. Three months after the cessation of the immunosuppressants, EBV-SMTs in the liver and lungs shrank slightly. To the best of our knowledge, this is the first report on the genomic profile of this rare tumor. The clinical course of our patient indicates that EBV can induce SMTs, and immunological suppression of EBV may inhibit the activity of these tumors.

CARMIL2 Immunodeficiency with Epstein Barr Virus Associated Smooth Muscle Tumor (EBV-SMT). Report of a Case with Comprehensive Review of Literature

Background: Primary immunodeficiency (PID) having defects related to lymphocyte cytotoxic pathway or T-cell dysfunction are well known for developing opportunistic infections and Epstein-Barr virus (EBV)-associated diseases. CARMIL2 deficiency is a recently described combined immunodeficiency (CID) disorder characterized by defective CD28-mediated T cell co-stimulation, altered cytoskeletal dynamics, susceptibility to various infections and Epstein Barr Virus smooth muscle tumor (EBV-SMT). Case report: We report a homozygous CARMIL2 pathogenic variant presenting with recurrent infections and EBV associated smooth muscle tumor (SMT) in a child. Conclusion: The present study reports that EBV SMT may occur in a child with CARMIL2 deficiency.

Epstein-Barr Virus-Positive Langerhans Cell Sarcoma: Is There a Link? A Case Report

Langerhans cell sarcoma (LCS) is an extremely rare, malignant neoplasm that originates from Langerhans cells (LCs). Fewer than 70 cases have been reported in the English-language literature. LCS typically involves multiple organs, including the skin, lymph nodes, lungs, bone, bone marrow, liver, spleen, and soft tissues. Several etiological factors for LCS have been proposed, including immunosuppression, virus infection, and prior hematological disease. We report a rare case of LCS with Epstein-Barr virus (EBV) infection; bilateral cervical giant cysts were the initial manifestation. To our knowledge, this is the first report of LCS with EBV infection. The case information was complete, and the relevant literature was reviewed to gain insight into LCS. The case raises new questions on the oncogenic character of EBV.

Adoptive Cell Transfer of Allogeneic Epstein–Barr Virus-Specific T Lymphocytes for Treatment of Refractory EBV-Associated Posttransplant Smooth Muscle Tumors: A Case Report

Posttransplant smooth muscle tumors (PTSMTs) are rare Epstein–Barr virus (EBV)-associated neoplasms, mostly occurring after solid organ transplantation. Current therapeutic strategies include surgery and reduction of immunosuppressive medication. We describe for the first time a novel treatment approach for PTSMT by adoptive cell transfer (ACT) of EBV-specific T cells to a 20-year-old patient with a medical history of cardiac transplantation, posttransplant lymphoproliferative disease, and multilocular PTSMT. During ACT, mild cytokine release syndrome occurred, while no unexpected safety signals were recorded. We observed in vivo expansion of EBV-specific T cells and reduction of EBV viremia. Best response was stable disease after 4 months with reduction of EBV viremia and normalization of lactate dehydrogenase levels. ACT with EBV-specific T cells may be a safe and efficacious therapeutic option for PTSMT that warrants further exploration.

Primary intracranial smooth muscle tumor associated with Epstein-Barr virus in immunosuppressed children: two cases report and review of literature

Primary intracranial smooth muscle tumors are rare. Most cases are related to Epstein-Barr virus proliferation in immunocompromised patients such as organ solid recipients. Only a few cases have been reported in pediatric patients. The clinical features are very variable depending mainly on the location and size of the smooth muscle tumor (SMT) and the pathogenesis is poorly understood. We describe two cases of intracranial SMT localized in the temporal lobe and associated with EBV in immunosuppressed children. A review of the literature associated with intracranial leiomyomas was also done.

Case history on Epstein-Barr Virus-associated smooth muscle tumor (EBV-SMT) of cranio-cervical junction in an immunocompetent patient

Epstein-Barr virus-associated smooth muscle tumor (EBV-SMT) is a rare mesenchymal tumor that almost exclusively occurs in immunocompromised hosts. Here, we report a 75-year-old Taiwanese woman without definite immune-deficient history presenting with progressive occipital neuralgia, low cranial nerve deficits (CN9-12) and cervical (C1-C5) radiculopathy. Magnetic resonance imaging revealed a 4.5*4.0*6.7 cm infiltrating mass occupying posterior skull base and C1-C2 vertebra and C1-5 epidural extension with bone destruction and vertebral artery (VA) encasement. There was also a synchronous 2.7 cm tonsillar tumor. A two-stage operation for cranio-cervical tumor excision and stabilization was performed. Tumor was confirmed directly arising from VA intraoperatively. Pathology reported a spindle cell neoplasm and the diagnosis of EBV-SMT was confirmed by EBER (EBV-encoded small RNA) in situ hybridization. An immune survey and reconstruction should be conducted for patient with EBV-SMT. A near-total resection of tumor may be beneficial for local control, however, the role of surgical resection in treating CNS EBV-SMT remains to be determined.

Virus-Driven Carcinogenesis

Cancer arises from the accumulation of genetic and epigenetic alterations. Even in the era of precision oncology, carcinogens contributing to neoplastic process are still an important focus of research. Comprehensive genomic analyses have revealed various combinations of base substitutions, referred to as the mutational signatures, in cancer. Each mutational signature is believed to arise from specific DNA damage and repair processes, including carcinogens. However, as a type of carcinogen, tumor viruses increase the cancer risk by alternative mechanisms, including insertional mutagenesis, viral oncogenes, and immunosuppression. In this review, we summarize virus-driven carcinogenesis to provide a framework for the control of malignant cell proliferation. We first provide a brief overview of oncogenic viruses and describe their implication in virus-related tumors. Next, we describe tumor viruses (HPV, Human papilloma virus; HBV, Hepatitis B virus; HCV, Hepatitis C virus; EBV, Epstein-Barr virus; Kaposi sarcoma herpesvirus; MCV, Merkel cell polyoma virus; HTLV-1, Human T-cell lymphotropic virus, type-1) and tumor virus-related cancers. Lastly, we introduce emerging tumor virus candidates, human cytomegalovirus (CMV), human herpesvirus-6 (HHV-6) and adeno-associated virus-2 (AAV-2). We expect this review to be a hub in a complex network of data for virus-associated carcinogenesis.

Epstein-Barr Virus-Associated Smooth Muscle Tumors of Larynx: A Clinicopathologic Study and Comprehensive Literature Review of 12 Cases

Laryngeal mesenchymal neoplasms are rare, with smooth muscle tumors comprising a small subset. Specifically, Epstein-Barr virus (EBV)-associated smooth muscle tumors are exceptionally rare, lacking a comprehensive evaluation of their clinical and histologic features. Two patients (a 59 year old male and 51 year old female) had received renal transplants 156 and 240 months, respectively prior to onset of laryngeal symptoms. Supraglottic polypoid masses were identified and removed conservatively. Histologically, the tumors were hypercellular, showing alternating light and dark areas, the latter composed of primitive appearing round cells, while a more characteristic spindled tumor cell population was noted in the remaining areas. Cytoplasmic vacuoles were noted adjacent to the nucleus. There was no tumor necrosis or pleomorphism, but increased mitotic figures (11-12/2 mm²) were seen, without atypical forms. The tumor cells were strongly immunoreactive with smooth muscle actin and smooth muscle myosin heavy chain and with Epstein-Barr virus encoded RNA (EBER) by in situ hybridization. These patients were reviewed in the context of a thorough English literature review, which demonstrates a wide age range at presentation without a sex predilection, but with most patients from specific ethnic groups (Chinese, Thai, Pilipino). Three-quarters of patients are part of multifocal disease and the majority are post-renal transplantation patients. Conservative management seems to yield the best overall outcome for these indolent tumors. In conclusion, EBV-associated smooth muscle tumors should be considered in any immunocompromised patient with a head and neck smooth muscle tumor, especially when EBER is documented by in situ hybridization. Conservative management may be employed, even when multifocal tumors are documented.

Role of surgery in treating epstein-barr virus-associated smooth muscle tumor (EBV-SMT) with central nervous system invasion: A systemic review from 1997 to 2019

Epstein-Barr virus-associated smooth muscle tumor (EBV-SMT) is a rare mesenchymal tumor occurred almost exclusively in immunocompromised hosts. This article provides a systematic review of literature under PRISMA guideline on clinical features, treatment modalities, roles of surgical intervention, and outcomes of all 65 reported EBV-SMTs with central nervous system (CNS) invasion. Over 95% of reported cases were immunocompromised, while human immunodeficiency virus infection and post-organ transplantation were the most commonly associated underlying causes (near 90%). Despite a heterogeneous follow-up period, a 1-year survival rate of 76.0% and 5-year survival rate of 59.6% may support the indolent and non-deadly nature of EBV-SMT even with CNS invasion. Immune survey and reconstruction should be conducted for every patient with CNS EBV-SMT. Surgical resection is mostly adopted as primary treatment to obtain diagnosis and relieve compressive effect. A total resection of tumor may be beneficial if tumor was symptomatic and had intracranial invasion.

Epstein-Barr virus-associated smooth muscle tumor in a kidney transplant recipient: A case-report and review of the literature

INTRODUCTION

Epstein-Barr virus (EBV) is a herpesvirus linked to pre-malignant lymphoproliferative diseases and up to nine distinct human tumors. The most frequent EBV-associated malignancies are lymphomas and nasopharyngeal carcinoma. By promoting smooth muscle proliferation, EBV can induce EBV-associated smooth muscle tumors (SMT) which remain a very rare oncological entity. This study reports one case report of SMT and aims to offer the largest review of literature on post-transplantation-SMT (PT-SMT) in kidney transplant recipients, with a focus on therapeutic management and evolution of graft function.

METHODS

Case reports and case series of PT-SMT in kidney transplant recipients were collected from 1996 to 2019.

RESULTS

A total of 59 PT-SMT were evaluated. The median time at diagnosis was 74.6 months after kidney transplantation. The most frequent localizations were liver and lung. EBV seroconversion was notified in all six patients with previously negative status. Preferred therapeutic option was surgery (65.9%), associated with a reduction in immunosuppression (77.2%), which includes switch to mTOR inhibitors (29.5%), and discontinuation of MMF (32%). In our review, 13% of patients experienced rejection, 8.7% lost their graft and went back on hemodialysis; 8.8% of patients died of PT-SMT.

CONCLUSION

PT-SMT is a rare but serious condition in kidney transplant recipients. EBV seroconversion following transplantation appears as a risk factor in developing PT-SMT in solid-organ recipients. In the absence of guidelines, therapeutic management for PT-SMT is challenging and exposes the patient to high risk of graft loss.

Tumor Microenvironment Conditioning by Abortive Lytic Replication of Oncogenic γ-Herpesviruses

Epstein Barr virus (EBV) and Kaposi sarcoma-associated herpesvirus (KSHV) constitute the human γ-herpesviruses and two of the seven human tumor viruses. In addition to their viral oncogenes that primarily belong to the latent infection programs of these viruses, they encode proteins that condition the microenvironment. Many of these are early lytic gene products and are only expressed in a subset of infected cells of the tumor mass. In this chapter I will describe their function and the evidence that targeting them in addition to the latent oncogenes could be beneficial for the treatment of EBV- and KSHV-associated malignancies.

Epstein-Barr Virus-Associated Smooth Muscle Tumour: A Case Series with a Significant Proportion of Tumours Showing Proclivity for Cutaneous Soft Tissues

Background

Epstein-Barr virus-associated smooth muscle tumours (EBV-SMTs) are rare neoplasms of uncertain biological potential. They are seen in the setting of immune suppression from a variety of causes, including HIV infection and post-transplant immunosuppression. Most of the literature pertaining to these neoplasms comprises case reports and small case series, with a dearth of documented cases from South Africa.

Objective

To expand on the literature of these rare neoplasms in the South African context, with an emphasis on a subset showing a predilection for the cutaneous soft tissues.

Method

Twenty-one EBV-SMTs from 19 consecutive patients were retrieved from the archives of the Division of Anatomical Pathology in the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, and the National Health Laboratory Service. Clinical and pathological characteristics of each case were recorded, including patient age, tumour site, H&E morphology, immunophenotypic features and the tumoural EBV status.

Results

The patients' ages ranged from 12 to 63 years, with a mean of 36 years. Thirteen (68%) of the patients in whom the HIV status was known were HIV-positive. Two of the 19 patients each had 2 tumours, thus accounting for the total of 21 neoplasms studied. Although 12 of the 21 tumours (57.1%) were from a variety of visceral organs, 9 (42.9%) originated in the dermis and superficial subcutaneous tissues, making the cutaneous soft tissues the most commonly affected site. Morphologically, all of the neoplasms were characterised by fascicles of myoid cells, admixed rounder tumour cells, scattered intratumoural lymphocytes and variable immunohistochemical staining with markers of smooth muscle differentiation. All 21 neoplasms were proven to harbour EBV DNA.

Conclusion

A significant proportion of EBV-SMTs may present in the cutaneous soft tissues. This neoplasm should, therefore, be included in the histopathological differential diagnosis of any cutaneous or superficial subcutaneous spindle cell tumour, especially in patients with a history of underlying immune suppression. Accurate diagnosis thereof and its distinction from other spindle cell neoplasms is important in view of management implications and the potential for multicentricity in some patients.

Treatment response with sirolimus for a pediatric patient with an EBV-associated smooth-muscle tumor after bone marrow transplantation

Epstein-Barr virus-associated smooth-muscle tumors (EBV-SMTs) are unique and rare neoplasms described in immunocompromised patients. The case describes a nine-year-old female with a history of acute lymphoblastic leukemia with relapse and subsequent allogeneic bone marrow transplantation who presented with multiple EBV-SMTs of the liver. EBV utilizes the mammalian target of rapamycin (mTOR) pathway for tumor growth, and sirolimus, a mTOR inhibitor, has shown to result in a short-term response. We now report an extended treatment response with sirolimus in a pediatric patient with an EBV-SMT.

Multiple Epstein-Barr Virus-associated Smooth Muscle Sarcomas of the Gut in a Child Treated for Acute Lymphoblastic Leukemia

A 7-year-old boy with a history of low-risk acute lymphoblastic leukemia developed multiple intussusceptions shortly after the end of maintenance therapy. Explorative laparotomy showed >10 polyps in the small intestine. Histologic examination revealed intestinal smooth muscle sarcomas associated with Epstein-Barr virus. The patient recovered well after partial cuneiform resection of the largest polyps and treatment with sirolimus. This case report indicates that these tumors may arise even after moderate transient immunosuppression and that association with acute lymphoblastic leukemia is possible although rarely described. We discuss the potential benefit of the mTor/Akt signal inhibitors as treatment for these tumors.

Favourable outcome of AIDS-related multi-centric central nervous system Epstein-Barr virus-associated smooth muscle tumour with surgery and adjuvant radiation therapy: a case study and literature review

Epstein-Barr virus-associated smooth muscle tumour (EBV-SMT) is a unique condition which affects immunocompromised patients. We describe the favourable outcome of a patient with acquired immune deficiency syndrome (AIDS)-related multi-centric EBV-SMT involving the posterior fossa and spine treated with surgery and adjuvant volumetric modulated arc therapy comprising 50 Gy in 25 fractions to four sites initially to the brain and lumbar spine followed by sixth to ninth thoracic vertebrae (T6-T9) and sacrum a year later. Reported literature suggests that AIDS-related EBV-SMTs are more sensitive to radiotherapy. However, compliance to the highly active anti-retroviral therapy is paramount in preventing future recurrence. This case also emphasises the importance of multidisciplinary management in ensuring the best possible outcome.

Spleen Tyrosine Kinase Inhibitor TAK-659 Prevents Splenomegaly and Tumor Development in a Murine Model of Epstein-Barr Virus-Associated Lymphoma

The novel SYK and FLT3 inhibitor TAK-659 prevents the enlargement of spleen and tumor development in a mouse model of EBV-associated lymphoma by counteracting the activation of cellular kinase SYK through the viral LMP2A gene by inducing cell death in tumor cells but not in nontumor cells. These findings indicate that TAK-659 may be a very effective nontoxic therapeutic molecule especially for EBV-positive hematologic malignancies.

Epstein-Barr virus (EBV) is associated with several B and epithelial cell cancers. EBV-encoded latent membrane protein 2A (LMP2A) contributes to cellular transformation by mimicking B cell receptor signaling. LMP2A/MYC double transgenic mice develop splenomegaly and B cell lymphoma much faster than MYC transgenic mice do. In this study, we explored the potential therapeutic efficacy of a novel spleen tyrosine kinase (SYK) and FLT3 inhibitor TAK-659 for development of a treatment option for EBV-associated malignancies. In our transgenic model, TAK-659 treatment totally abrogated splenomegaly and tumor development in LMP2A/MYC mice in both pretumor and tumor cell transfer experiments. TAK-659 treatment killed tumor cells, but not host cells within the spleen and tumors. Furthermore, TAK-659 treatment abrogated metastasis of tumor cells into bone marrow. Our data also show that TAK-659 inhibits SYK phosphorylation and induces apoptosis in LMP2A/MYC tumor cells at low nanomolar concentrations. Therefore, TAK-659 may provide an effective therapeutic option for treatment of LMP2A-positive EBV-associated malignancies and should be explored further in clinical trials.

IMPORTANCE The novel SYK and FLT3 inhibitor TAK-659 prevents the enlargement of spleen and tumor development in a mouse model of EBV-associated lymphoma by counteracting the activation of cellular kinase SYK through the viral LMP2A gene by inducing cell death in tumor cells but not in nontumor cells. These findings indicate that TAK-659 may be a very effective nontoxic therapeutic molecule especially for EBV-positive hematologic malignancies.

Non-canonical WNT6/WNT10A signal factor expression in EBV+ post-transplant smooth muscle tumors

Post-transplant smooth muscle tumors (PTSMTs) are rare mesenchymal neoplasms which occur after solid organ or haematopoietic stem cell transplantation. PTSMT typically consist of Epstein–Barr-virus (EBV)+ smooth muscle-like cells and show an intermediate malignancy. Their main occurrences are visceral organs, especially the liver, but intracranial appearances are described and associated with a poor prognosis. EBV drives the growth of PTSMT; however, the underlying molecular mechanisms still remain unclear. Gene expression analysis of a set of morphologically similar tumors (leiomyomas, leiomyosarcomas, angioleiomyomas and endothelial haemangiomas) from patients without immunosuppression or EBV-association was performed. Our findings indicate that PTSMT’s growth is driven by two factors of the wingless-type protein family: WNT6 and WNT10A. We are first to report that in PTSMTs, a non-canonical activation of WNT, independent of beta-catenin, drives tumor cell proliferation via MTOR/AKT1, MYC and Cyclin D2.

Epstein-Barr virus-associated smooth muscle tumor involving the spine of an HIV-infected patient: Case report and review of the literature

Within the last two decades, there have been multiple reports of Epstein-Barr virus (EBV)-associated smooth muscle tumors in immunocompromised patients. This includes HIV-infected patients, post-transplant patients, and patients with congenital defects of their immune systems. Here we report the case of a 24-year-old African American female with congenital HIV presenting with progressive lower extremity weakness, constipation, aching pain in her shoulders, and subcostal anesthesia. Magnetic resonance imaging (MRI) revealed a large circumferential lesion extending from T1-T3 and a smaller left paraspinal lesion at C6-C7. The T1-T3 mass was excised via a right-sided costotransversectomy with laminectomy and fusion from T1-T3. Highly active antiretroviral therapy (HAART) was started postoperatively, and adjuvant radiotherapy was initiated but patient was lost to follow-up. Surgical pathology demonstrated a smooth muscle tumor diffuse nuclear positivity for EBV-encoded small RNA 1 by in situ hybridization. Although eight studies have reported HIV patients with EBV-associated smooth muscle tumors of the spine, to the author's knowledge, this is the first review comprised solely of patients with spinal involvement with the addition of our patient case.

Epstein-Barr Virus+ Smooth Muscle Tumors as Manifestation of Primary Immunodeficiency Disorders

Epstein–Barr virus positive (EBV⁺) smooth muscle tumors (SMTs) constitute a very rare oncological entity. They usually develop in the context of secondary immunodeficiency caused by human immunodeficiency virus infection or immunosuppressive treatment after solid organ transplantation. However, in a small fraction of predominantly pediatric patients, EBV⁺ SMTs may occur in patients with primary immunodeficiency disorders (PIDs), such as GATA2 and CARMIL2 deficiency. In secondary immunodeficiencies and when the underlying condition can not be cured, the treatment of EBV⁺ SMTs is based on surgery in combination with antiretroviral and reduced or altered immunosuppressive pharmacotherapy, respectively. Importantly, without definitive reconstitution of cellular immunity, long-term survival is poor. This is particularly relevant for patients with EBV⁺ SMTs on the basis of PIDs. Recently, allogeneic hematopoietic stem cell transplantation resulted in cure of immunodeficiency and EBV⁺ SMTs in a GATA2-deficient patient. We propose that in the absence of secondary immunodeficiency disorders patients presenting with EBV⁺ SMTs should be thoroughly evaluated for PIDs. Allogeneic hematopoietic stem cell transplantation should be taken into consideration, ideally in the setting of a prospective clinical trial.

A rare case of Epstein-Barr virus-associated hepatosplenic smooth muscle tumors after kidney transplantation

A 27-year old caucasian male was diagnosed 2.7 years after kidney transplantation with Epstein-Barr virus (EBV)-associated smooth muscle tumors in liver and spleen. The reduction in immunosuppression and conversion from tacrolimus to sirolimus did not lead to a regression of the tumors. Additionally, the patient developed a cellular rejection of his renal allograft, which was successfully treated. A combined approach with stereotactic radiofrequency ablation (SRFA) and surgical resection was effective in the treatment of the tumors.

Concomitant Epstein-Barr Virus-associated smooth muscle tumor and granulomatous inflammation of the liver

Epstein-Barr Virus-associated smooth muscle tumor (EBV-SMT) is a rare mesenchymal tumor typically seen in immunocompromised patients. Here, we report a case of EBV-SMT and associated granulomatous inflammation in the liver of a 32-year-old man with history of human immunodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS). To our knowledge, an association of these two lesions has not been previously reported. We review the literature and discuss pathogenesis, differential diagnosis and immunohistochemical (IHC) stains helpful for the diagnosis of this rare entity. Finally, we consider possible explanations for the concomitant presence of these lesions.

Epstein-Barr virus–associated smooth muscle tumor of the cavernous sinus: a delayed complication of allogenic peripheral blood stem cell transplantation: case report

Epstein-Barr virus (EBV)–associated smooth muscle tumors (SMTs) have recently been associated with primary and secondary immunodeficiencies. They are broadly divided into 3 subgroups: HIV-related, posttransplant, and congenital immunodeficiency. Subsequent to organ transplantation and acquired immunosuppression, a few cases of EBV-associated SMTs have been described in the liver, respiratory tract, and gastrointestinal system. To the authors' knowledge, intracranial involvement after peripheral blood stem cell transplantation has never been reported previously. The authors describe the case of a 65-year-old woman who presented with recent-onset painful ophthalmoplegia. She had a prior history of acute myelogenous leukemia requiring allogenic peripheral blood stem cell transplantation 2 years earlier, but she was in a remission phase. Imaging revealed a T1/T2 isointense, homogeneously enhancing lesion of the left cavernous sinus. A presumptive diagnosis of Tolosa-Hunt syndrome was made, and she was treated with steroids; however, her symptoms progressed quickly and repeat imaging revealed that the lesion was growing. To rule out leukemic deposits, a minimally invasive lateral orbitotomy extradural transcavernous approach was performed for biopsy sampling and debulking of the lesion. The biopsied tumor tissue was found to be infiltrative, grayish, firm, and moderately vascular. The final pathology results indicated an EBV-associated SMT of the cavernous sinus. Subsequently, the patient's steroid treatment was stopped and she had obtained partial symptomatic relief at her last follow-up visit, 3 months after surgery. EBV-associated SMT should be included in the differential diagnosis for intracranial and dural-based central nervous system lesions, especially in immunocompromised patients. Paradoxical response to steroids with worsening of symptoms is a hallmark of EBV-associated SMTs.

Epstein-Barr Virus-Associated Smooth Muscle Tumor

Immunodeficient individuals are prone to develop a number of opportunistic infections and unique neoplasms. Epstein-Barr virus-associated smooth muscle tumor is an uncommon neoplasm associated with immunodeficiency. It has been described in patients infected with human immunodeficiency virus, in the posttransplant setting, and in those with congenital immunodeficiency. Different anatomic sites can be involved by Epstein-Barr virus-associated smooth muscle tumor, and even multiple locations can contain these unique lesions within the same patient. The presence of variable numbers of intratumoral lymphocytes and primitive round cell areas are the unique defining features for this tumor. Histopathologic features may vary considerably in terms of cellular atypia, mitotic activity, and necrosis, with no correlation to the clinical behavior. Demonstration of Epstein-Barr virus infection by in situ hybridization within tumor cell remains critical for the diagnosis. The mechanism for Epstein-Barr virus infection of progenitor cells and neoplastic transformation has been an area of interest and conjecture. Different treatment strategies are proposed according to underlying disease status. This paper reviews the clinicopathologic features of this uncommon neoplasm with detailed discussion of the role of Epstein-Barr virus in the pathogenesis.

EBV-associated hepatic smooth muscle tumor of uncertain biologic behavior after heart transplantation in a pediatric patient: case report

Epstein-Barr virus-associated smooth muscle tumor (EBV-SMT) is a rare neoplasm recognized in immunocompromised patients. There are less than 30 cases of EBV-SMT reported in pediatric population following solid organ transplantation. Herein, we report a case of an 8-year-old female who was incidentally noted to have multiple lesions in the liver 8 years after heart transplantation. The tumor was composed of a cellular proliferation of spindle-shaped cells with low mitotic activity. The diagnosis of EBV-SMT was confirmed by in situ hybridization for EBV-encoded small RNA (EBER) transcripts. Multiple additional lesions were detected by whole body positron emission tomography-computed tomography (PET-CT) scan 4 months after the initial finding of the hepatic lesions. Immunosuppression was switched to a mechanistic target of rapamycin (mTOR) inhibitor. We conclude that EBV-SMT should be included in the differential diagnoses in post-transplantation patients and further investigations should be performed to evaluate additional lesions.

Epstein-Barr virus-associated smooth muscle tumors in children following solid organ transplantation: a review

EBV-SMT are a rare entity following organ transplantation. Given the rarity of the tumor, there is no standard approach to diagnosis and treatment. A literature search identified 28 reported cases of EBV-SMT in addition to our own experience with one case. The aim of this review is to summarize the existing data regarding pathogenesis, diagnosis, and treatment.

The immunology of Epstein-Barr virus-induced disease

Epstein-Barr virus (EBV) is usually acquired silently early in life and carried thereafter as an asymptomatic infection of the B lymphoid system. However, many circumstances disturb the delicate EBV-host balance and cause the virus to display its pathogenic potential. Thus, primary infection in adolescence can manifest as infectious mononucleosis (IM), as a fatal illness that magnifies the immunopathology of IM in boys with the X-linked lymphoproliferative disease trait, and as a chronic active disease leading to life-threatening hemophagocytosis in rare cases of T or natural killer (NK) cell infection. Patients with primary immunodeficiencies affecting the NK and/or T cell systems, as well as immunosuppressed transplant recipients, handle EBV infections poorly, and many are at increased risk of virus-driven B-lymphoproliferative disease. By contrast, a range of other EBV-positive malignancies of lymphoid or epithelial origin arise in individuals with seemingly intact immune systems through mechanisms that remain to be understood.

[Aberrant reparative tissue remodeling: histopathology and molecular pathology]

Not only tumorous infiltrations can lead to destruction of parenchymal organs but also the aberrant proliferation and matrix production of mesenchymal cells and vessels during a dysregulated repair attempt. This fibrogenesis is the result of a complex pathogenesis, which can be investigated in animal models but also in situ to harvest new biomarkers. This article deals particularly with the second method and summarizes molecular pathological findings in various model diseases for aberrant reparative tissue reconstruction. These model diseases include plexiform vasculopathy in pulmonary arterial hypertension (PAH), Quilty lesions in heart transplantation, bronchiolitis obliterans (BO), inflammatory airway remodeling and Epstein-Barr virus (EBV) induced smooth muscle proliferation (posttransplantation smooth muscle tumor, PTSMT).Using in situ molecular pathology, we were able to dismiss an assumed involvement of myofibroblastic cells in vessel reconstruction of the lung in PAH. We could also for the first time perform a comprehensive molecular characterization of the vascular remodeling and prove that plexiform vasculopathy represents a complex-regulated epiphenomenon of excessive pulmonary hypertension. This method also allowed us to describe for the first time the miRNA expression in PAH in a compartment-specific manner and to draw conclusions regarding the damaged overriding regulatory mechanisms. In the same way, we were also able to describe the chimeric character of the complex neoangiogenesis in the donor organ after heart transplantation.After lung transplantation, we identified for the first time a group of tissue-based molecular markers, which can predict later occurrence of BO even in morphologically normal transbronchial biopsies. In addition, we have documented for the first time the molecular characteristics of the morphologically analogous airway reconstruction in lung-transplanted and non-transplanted patients. We could further elucidate the role of matrix metalloproteinases (MMP) and their antagonists in inflammatory airway reconstruction and deduce from this the resulting therapeutic implications. Accordingly, we were able to further clarify the origin, pathogenesis and the malignant potential of EBV-induced PTSMT and for the first time provide an evidence-based therapy recommendation and risk assessment.In summary, this article documents that in situ diagnostics can meet the requirements of the challenging parameters and issues of life sciences. It is to be expected that the technical possibilities will develop analogously to the increasing demands and the in situ method will move further into the focus of molecular pathology.

Tumour angiogenesis in Epstein-Barr virus-associated post-transplant smooth muscle tumours

Epstein-Barr virus (EBV)-associated post-transplant smooth muscle tumours (PTSMT), are rare complications following organ/stem cell transplantation. Despite the mainly benign behaviour of PTSMT, alternative therapies are needed for those patients with progressive tumours. In tumours not approachable by surgery or reduction of immunosuppression, the angiogenic microenvironment might be a potential target of therapy, an approach that is well utilised in other soft tissue neoplasms. In a previous study, we evaluated the expression of EBV-related genes and the microRNA profile in PTSMT, but so far the characteristics of angiogenesis in PTSMT are not known. Therefore, the aim of this study was to evaluate the expression pattern of angiogenesis-related genes in PTSMT, in order to identify potential target molecules for anti-angiogenic therapy.PTSMT (n = 5 tumours) were compared with uterine leiomyomas (n = 7). Analyses included real-time PCR of 45 angiogenesis-associated genes, immunohistochemistry (CD31, prostaglandin endoperoxide synthase 1/PTGS1) and assessment of tumour vascularisation by conventional histopathology.PTSMT showed similar or fewer vessels than leiomyomas. Of the genes under investigation, 23 were down-deregulated (pro-angiogenic and some anti-angiogenic factors) and five were up-regulated (e.g. PTGS1 which is expressed at very low levels in leiomyomas but moderately higher levels in PTSMT).In summary, no particular target molecule could be identified, because tumour angiogenesis in PTSMT is characterised by low levels of major pro-angiogenic factors and there is no prominent increase in tumour vascularisation. EBV can induce angiogenesis via its viral late membrane protein 1 (LMP1) but PTSMT frequently do not express LMP1, which could be an explanation why, despite EBV infection, PTSMT show no exaggerated tumour angiogenesis.

Epstein-Barr virus-associated smooth muscle tumors in a composite tissue allograft and a pediatric liver transplant recipient

Epstein-Barr virus (EBV) is known to establish latent infections in B-lymphocytes that can cause lymphoproliferative disorders particularly in immunocompromised patients. More recently, the development of rare EBV-associated smooth muscle tumors has been reported in transplant recipients. We herein describe 2 new cases of EBV-associated post-transplant smooth muscle tumors (EBV-PTSMT), including the first in a facial composite tissue graft recipient. Among the striking features shared by these 2 patients were their young ages, the fact that they were naïve for EBV before the transplantation, that they developed a post-transplant lymphoproliferative disorder before the diagnosis of EBV-PTSMT, and that they responded favorably to reduction of immunosuppression. Radiological and histologic features of EBV-PTSMT are shown. Finally, pathophysiology and therapeutic management of EBV-PTSMT are discussed based on a comprehensive review of the literature.

MicroRNA expression in Epstein-Barr virus-associated post-transplant smooth muscle tumours is related to leiomyomatous phenotype

Epstein-Barr virus (EBV)-associated post-transplant smooth muscle tumours (PTSMT) are rare complications. In our previous molecular analysis, we have evaluated the expression of regulatory microRNA which are known to be EBV-related (miR-146a and miR-155) but found no deregulation in PTSMT. In this current analysis, we aimed to characterize the expression profiles of several hundred microRNA. Tissue samples from PTSMT and uterine leiomyomas were analysed by quantitative real-time PCR for the expression of 365 mature microRNA. PTSMT and leiomyomas share a highly similar microRNA profile, e.g. strong expression of miR-143/miR-145 cluster and low expression of miR-200c. Among EBV-related microRNA (miR-10b, miR-21, miR-29b, miR-34a, miR-127, miR-146a, miR-155, miR-200b, miR-203 and miR-429) only miR-10b and miR-203 were significantly deregulated. The expression pattern of microRNA in PTSMT is not associated with EBV infection but reflects the leiomyomatous differentiation of the tumour cells.

Epstein-Barr virus associated smooth muscle tumors in post transplant pediatric patients two cases of rare locations, and review of the literature

Epstein-Barr virus (EBV) may present few or no symptoms in immunocompetent individuals; however, in immunocompromised patients as in the case of AIDS and post-transplant patients, the virus occasionally stimulates neoplastic transformations. Epstein-Barr virus may play a role in the development of smooth muscle tumors (SMT). In the case of Epstein-Barr associated smooth muscle tumors (EBV+SMT), the virus is thought to be the leading factor to the tumorigenic pathway. We report two pediatric patients (6 and 13 years old) who underwent liver transplantation and developed EBV+SMT in the colon and orbit. These two cases represent rare locations for this kind of lesion.

Epstein-Barr virus-associated smooth muscle tumors after kidney transplantation: treatment and outcomes in a single center

BACKGROUND

Epstein-Barr virus-associated smooth muscle tumors (EBV SMT) in adult kidney transplant recipients (KTR) are rare. The aims of this study are to document the clinical features, types of treatment given, and outcomes of KTR with EBV SMT in our institution.

METHODS

Sixteen patients were identified from our institution's databases. Patients' survival, tumor outcome, and graft survival were compared between patients who remained on cyclosporine-based immunosuppressant and those who converted to sirolimus-based therapy.

RESULTS

The median time of diagnosis was 9.4 yr after kidney transplantation, and majority of the patients had multifocal disease at the time of diagnosis. Overall, the patient survival rate was 75% over a mean follow-up period of five yr. Two patients with non-functioning allograft at the time of diagnosis of EBV SMT were excluded from the treatment outcome analysis. Comparing the sirolimus (n = 7) vs. cyclosporine groups (n = 7), patient survival rate was 100% vs. 42.9% (p = 0.08), graft survival 71.4% vs. 28.7% (p = 0.53), and disease-free status 42.9% vs. 14.3% (p = 0.73), respectively.

CONCLUSION

Surgical resection in combination with decreasing immunosuppression or conversion to sirolimus appears to be effective in the treatment of EBV SMT in KTR.

Molecular and clinicopathological analysis of Epstein-Barr virus-associated posttransplant smooth muscle tumors

Epstein-Barr virus (EBV)-associated posttransplant smooth muscle tumors (PTSMT) are very rare complications. We aimed to provide a clinicopathological characterization which is based on our own case series (n = 5) as well as previously reported PTSMT cases (n = 63). Meta-analysis of PTSMT and molecular analysis of tumor cells from our cohort was performed. Most PTSMT developed in kidney-transplanted patients (n = 41/68, 60%). Liver/transplant liver was the main site of manifestation (n = 38/68, 56%). Tumors occurred after a median interval of 48 months (range 5-348) and developed earlier in children than in adults. Most tumors showed no marked cellular atypia, low mitosis rate and no tumor necrosis. Gene expression analysis of 20 EBV-related genes, including two microRNAs, revealed overexpression of MYC (p = 0.0357). Therapy was mainly based on surgical resection or reduced immunosuppression but no significant differences in overall survival were evident. Lower overall survival was associated with multiorgan involvement (n = 33/68, 48.5%) and particularly with intracranial PTSMT manifestation (n = 7/68, 10%; p < 0.02), but not transplant involvement (n = 11/68, 16%). In summary, PTSMT differ from conventional leiomyosarcomas by their lack of marked atypia, unusual sites of involvement and defining EBV association. Surgery and reduced immunosuppression show comparable clinical results and prognosis is associated with intracranial manifestation.

Dasatinib therapy results in decreased B cell proliferation, splenomegaly, and tumor growth in a murine model of lymphoma expressing Myc and Epstein-Barr virus LMP2A

Epstein-Barr virus (EBV) infection and latency has been associated with malignant diseases including nasopharyngeal carcinoma, Hodgkin lymphoma, Burkitt lymphoma, and immune deficiency associated lymphoproliferative diseases. EBV-encoded latent membrane protein 2A (LMP2A) recruits Lyn and Syk kinases via its SH2-domain binding motifs, and modifies their signaling pathways. LMP2A transgenic mice develop hyperproliferative bone marrow B cells and immature peripheral B cells through modulation of Lyn kinase signaling. LMP2A/λ-MYC double transgenic mice develop splenomegaly and cervical lymphomas starting at 8 weeks of age. We reasoned that targeting Lyn in LMP2A-expressing B cells with dasatinib would provide a therapeutic option for EBV-associated malignancies. Here, we show that dasatinib inhibits B cell colony formation by LMP2A transgenic bone marrow cells, and reverses splenomegaly and tumor growth in both a pre-tumor and a syngeneic tumor transfer model of EBV-associated Burkitt lymphoma. Our data support the idea that dasatinib may prove to be an effective therapeutic molecule for the treatment of EBV-associated malignancies.

Pediatric multifocal myofibroblastic tumors with involvement of the gallbladder: HIV- and Epstein-Barr virus-associated smooth muscle cell tumors

Epstein-Barr virus associated smooth muscle cell tumors are commonly found in immunocompromised patients. These tumors occur most commonly in patients with AIDS and with greater incidence in children. The incidence of gallbladder tumors in these patients is rare, however. We report the case of a 10-year-old female patient who presented to our unit. She is HIV positive and on antiretroviral treatment. She required an emergency cholecystectomy to relieve external compression of the common bile duct where an empyematous gallbladder was found. Histopathology confirmed the presence of an Epstein-Barr virus-associated smooth muscle tumor. She is noted to have other asymptomatic lesions. Surgical intervention is reserved for symptomatic lesions and improves the immunocompromised state, although there is a propensity for local recurrence of the tumor.

Epstein-Barr virus-associated adrenal smooth muscle tumors and disseminated diffuse large B-cell lymphoma in a child with common variable immunodeficiency: a case report and review of the literature

This article reports the clinical and the histological features in a 7-year-old girl affected by common variable immunodeficiency (CVID) who developed multiple Epstein-Barr virus-associated tumors, represented by bilateral adrenal smooth muscle tumors (EBV-SMT) and multifocal diffuse large B-cell lymphoma. The EBV-SMTs showed features compatible with a benign or at least a low-malignant potential neoplasm. A peculiar feature observed in both EBV-SMTs was the occurrence of numerous lymphocytes intermingled with the spindle cells, which consisted of CD3+ CD5+ T-cells, with a predominant cytotoxic CD8+ component. Interestingly, EBV status differed in the neoplasms, since the EBV-SMTs were negative for LMP1 and positive for EBER, whereas the B-cell lymphoma expressed both EBV markers. Furthermore, EBV-LMP1 deletion was positive only in the EBV-SMTs, thus indicating that these tumors were the consequence of 2 distinct, EBV-dependent transformations. Similarly, lymphocyte clonality assay also showed different clonal bands in different sites (skin and nasal cavity), suggesting the development of intratumoral mutations. Finally, the authors review all 127 previously reported EBV-SMT, with discussion of their clinical and pathological features.

AIDS-Related EBV-Associated Smooth Muscle Tumors: A Review of 64 Published Cases

The number of reported cases of smooth muscle tumor (SMT) arising in patients with AIDS has been increasing since the mid-1990s. The aim of this study is to characterize the epidemiology, clinical manifestations, pathologic features, prognosis and, management of Epstein-Barr virus-related SMT (EBV-SMT) in patients with AIDS. An English language literature search identified 53 articles including 64 reported cases of EBV-SMT. The majority of these reports involved patients who were young, severely immunosuppressed, and had multifocal tumors. The central nervous system was the most common site to be involved. Histologically, tumors had smooth muscle features and were immunoreactive for muscle markers and all but two tumors demonstrated the presence of EBV by either immunohistochemistry, in situ hybridization, and/or PCR. While mitoses and/or necrosis were used to separate leiomyoma from leiomyosarcoma, these features did not correlate with clinical outcome. Treatment included primarily resection, and less often radiotherapy, chemotherapy and highly active antiretroviral therapy (HAART). Overall, EBV-SMTs appear to have variable aggressiveness and clinical outcome and may exhibit a more favorable prognosis compared to conventional leiomyosarcoma. Tumor-related death from EBV-SMT occurred in only 4 of 51 patients.

Rapamycin reverses splenomegaly and inhibits tumor development in a transgenic model of Epstein-Barr virus-related Burkitt's lymphoma

Epstein-Barr virus (EBV) infection and latency has been associated with malignancies, including nasopharyngeal carcinoma and Burkitt's lymphoma. EBV encoded latent membrane protein 2A (LMP2A) is expressed in most EBV-associated malignancies and as such provides a therapeutic target. Burkitt's lymphoma is a hematopoietic cancer associated with the translocation of c-MYC to one of the immunoglobulin gene promoters leading to abnormally high expression of MYC and development of lymphoma. Our laboratory has developed a murine model of EBV-associated Burkitt's lymphoma by crossing LMP2A transgenic mice with MYC transgenic mice. Since LMP2A has been shown to activate the PI3K/Akt/mTOR pathway, we tested the therapeutic efficacy of mTOR inhibitor rapamycin on the tumors and splenomegaly in these double transgenic mice (Tg6/λ-MYC). We found that rapamycin reversed splenomegaly in Tg6/λ-MYC mice prior to tumor formation by targeting B cells. In a tumor transfer model, we also found that rapamycin significantly decreased tumor growth, splenomegaly, and metastasis of tumor cells in the bone marrow of tumor recipients. Our data show that rapamycin may be a valuable candidate for the development of a treatment modality for EBV-positive lymphomas, such as Burkitt's lymphoma, and more importantly, provides a basis to develop inhibitors that specifically target viral gene function in tumor cells that depend on LMP2A signaling for survival and/or growth.