Epstein-Barr virus infection in nasopharyngeal carcinoma.

Nasopharyngeal carcinoma develops with extremely high incidence in discrete populations and geographic locations. It is consistently associated with the ubiquitous Epstein-Barr herpesvirus (EBV). The structure of EBV DNA indicates that the tumor is a clonal proliferation that developed subsequent to EBV infection. Specific viral genes are consistently expressed within all cells of the tumor. This consistent expression may indicate that the viral gene products are required for tumor growth. Genetic or environmental factors may affect the expression of these critical viral genes or cellular genes and contribute to tumor progression.