Western thymomas lack Epstein-Barr virus by Southern blotting analysis and by polymerase chain reaction

The authors investigated 16 western thymomas, 9 from the United States and 7 from Europe, for the presence of Epstein-Barr virus (EBV) DNA sequences by both Southern blot hybridization analysis and polymerase chain reaction using EBV-specific DNA probes that detect the long internal repeat and terminal repeat regions and the EBNA-1 gene. None of the 16 thymomas contained evidence of the EBV genome, even though we could detect EBV by Southern blotting when EBV DNA represents less than or equal to 1% of the total DNA and by polymerase chain reaction when a single EBV-positive cell is present among 10(5) EBV-negative cells. These results fail to demonstrate EBV genome in western thymomas and stand in contrast to those of McGuire et al (Am J Pathol 1988, 131:385) who previously reported that the EBV genome is present in thymomas occurring in southern Chinese patients. Therefore EBV does not appear to be implicated in the pathogenesis of all thymomas. The presence of EBV in eastern thymomas, regions where EBV is endemic may be due to epidemiologic factors and/or genetic predispositions.