Frequent presence of latent Epstein-Barr virus infection in peripheral T cell lymphomas. A review.

Two-hundred and four cases of peripheral T cell lymphoma (PTCL) occurring in Europeans without any sign of HIV-infection were investigated for their association with an Epstein-Barr virus (EBV) infection. Polymerase chain reaction (PCR) was applied for EBV-DNA detection, in situ hybridisation (ISH) for the cellular localization of EBV-encoded small nuclear RNA (EBER) and immediate early gene expression (BHLF) and immunohistology (IH) for the detection of EBV-encoded latent membrane protein 1 (LMP1) and EBV nuclear antigen 2 (EBNA2) expression. PCR and EBER-ISH produced congruent results in almost all cases with amplifiable DNA, leading to the finding of an overall frequency of EBV presence in 87/204 (42.6%) of the PTCL cases. Through EBER-ISH, the virus was identified to be exclusively present in small and blastic bystander lymphocytes in 29 cases, whilst an additional infection of neoplastic T cells was observed in the remaining 58 EBV-positive cases. The entity presenting with the most frequent EBV infection of tumour cells was that of angioimmunoblastic type PTCL, whilst the primary cutaneous PTCLs only seldom harbored the virus. Forty-eight of the EBV-positive TCLs showed an infection of a small proportion (1-20%) of the tumour cell population, whilst another ten cases, belonging to the pleomorphic TCL (PMTCL) group, displayed an infection of several to almost all neoplastic T cells (20-100%). Additional lytic EBV-infected cells could be detected in four cases by BHLF-ISH. LMP1 expression was present in a small proportion of the neoplastic T cells in 24 of the 58 cases with tumour cell infection, whilst an EBNA2 expression was detectable only in one case. Some non-malignant EBV-infected B-immunoblasts and Hodgkin/Reed Sternberg-like cells also expressed LMP1 in several cases. Our data imply a role of EBV in the pathogenesis of only a few PMTCL cases with predominant tumour cell infection, whilst the pathogenic significance of an EBV infection in the other PTCLs remains unclear due to the usually partial infection of the neoplastic cell component.