Absence of latent Epstein-Barr virus in thymic epithelial tumors as demonstrated by Epstein-Barr-encoded RNA (EBER) in situ hybridization
Background: Several studies have established that Epstein-Barr virus (EBV) is associated with lymphoproliferative disorders such as Burkitt's lymphoma and Hodgkin's disease. EBV is also present in undifferentiated nasopharyngeal carcinomas and in tumors of similar morphology (lymphoepithelioma-like carcinomas) arising in a variety of organs, predominantly in stomach, salivary gland and thymus. As reports of EBV-positive thymic epithelial tumors (TET) have been divergent and as different methods have been used to detect EBV, the aim of this study was to investigate the possible role of EBV in TET of Danish patients. Material and methods: Archival material of 157 cases of TET (105 thymomas and 52 thymic carcinomas, including 4 lymphoepithelioma-like thymic carcinomas (LELTC)) was analyzed for EBV by applying a sensitive and specific method for detecting latently EBV-infected cells (in situ hybridization for EBV-encoded RNA (EBER)). Results: All investigated cases were EBER negative. Conclusions: EBV does not seem to be implicated in the pathogenesis of TET. However, a review of the literature showed that 28% of LELTC were EBER ISH positive. As they occurred in young people (mean 18 years), at an age when the patients were susceptible to infection by EBV, it is suggested that EBV merely acts as an innocent bystander.