Epstein-Barr virus in T and natural killer (NK) cell non-Hodgkin's lymphomas.

Several studies using sensitive in situ hybridization techniques show that, in non-immunocompromised patients, Epstein-Barr virus (EBV) is more frequently detected in lymphomas expressing T cell markers than in B cell lymphomas. Among lymphomas expressing T cell markers, the presence of EBV is highly related to the site of origin of the tumor, being found in nearly all sinonasal lymphomas, in only a proportion of Waldeyer's ring, lung, gastrointestinal and nodal lymphomas, and undetectable in most primary cutaneous lymphomas. The role of EBV in their pathogenesis can be suggested in at least a proportion of extranodal lymphomas (nasal, lung, Waldeyer's ring, gastrointestinal) with T cell markers in which EBV genome is found in most if not all tumor cells (EBV-associated lymphomas) and the transforming LMP-1 protein is frequently expressed. Among these, sinonasal lymphomas constitute a distinct clinicopathologic entity which may present as lethal midline granuloma, are strongly associated with EBV and can be regarded in most cases as true NK cell lymphomas.