Incidence of latent infection of Epstein–Barr virus in lung cancers—an analysis of EBER1 expression in lung cancers by in situ hybridization

To evaluate the presence of Epstein–Barr virus (EBV) in lung cancers of Japanese patients, 81 lung cancers were examined using a highly sensitive in situ hybridization (ISH) method, employing an antisense oligonucleotide probe for EBV-encoded small nuclear RNA-1 (EBER). EBER1 expression was demonstrated in one poorly differentiated squamous cell carcinoma associated with marked lymphoid stroma (PDSCC-LS), two well differentiated adenocarcinomas, and two moderately differentiated squamous cell carcinomas, but was not detectable in other lung cancers, including small cell carcinomas. Unlike lymphoepithelioma-like undifferentiated carcinoma (LELC) of the lung, the PDSCC-LS consisted of poorly differentiated cells with distinct cell borders and nuclei with a coarse chromatin pattern and some prominent nucleoli. Most of the cancer cells expressed intense EBER1 signals. Although small to moderate numbers of cells positive for EBER1 were present in two adenocarcinomas and two squamous cell carcinomas, EBER1 signals varied in intensity and number in these four cases. Although polymerase chain reaction (PCR) and Southern blot hybridization with a ³²P-labelled probe internal to the primers were conducted to detect the EBV genome in 24 lung cancers, including five EBER1-positive cases, the genome was found to be positive in the five cases with EBER1-positive staining, including the PDSCC-LS, two adenocarcinomas and two squamous cell carcinomas, but not in the other cases. This study indicates that the morphological features of EBV-associated lung cancers are not restricted to the typical LELC type.