Epstein-Barr virus infection in the pathogenesis of nasopharyngeal carcinoma

Nasopharyngeal carcinomas (NPC) belong to the most frequent malignant tumours in certain parts of the world, e.g., south-east Asia, while they occur infrequently in western Europe. The association of NPCs with Epstein-Barr virus (EBV),a transforming human herpes virus, is well established. The current WHO classification recognises two major NPC histotypes, non-keratinising NPC and squamous cell NPC. EBV is invariably present in non-keratinising NPCs and the viral oncoprotein LMP-1 (latent membrane protein-1) is expressed in some cases. The tumour cells of: non-keratinising NPCs show phenotypic features which are inducible by LMP-1 in vitro. These may contribute to the development of the lymphoid stroma which is characteristic of this tumour type. Furthermore,the virus is detectable in nasopharyngeal carcinoma in situ. Thus,the virus is likely to be involved in the pathogenesis of non-keratinising NPCs. By contrast, the association of squamous cell NPCs with EBV displays a geographical variability. It appears, therefore, that squamous cell NPCs are a heterogenous group of tumours distinct from non-keratinising NPCs.