Using in situ hybridization assay, we examined Epstein-Barr virus (EBV) encoded RNA (EBER) expression in 66 cases of oral cancer, 40 esophageal cancer cases, 150 stomach cancer cases, and 46 colorectal cancer cases diagnosed in the Pathology Department of Port Moresby General Hospital, University of Papua New Guinea during the period between 1986-2002. There were no malignancies with positive EBER expression except for the following two male stomach cancer cases: a male case with a gastric carcinoma in pylorus whose age was unknown; and a male case aged 55 years without information on location of tumor. Both cases were histologically classified as non-solid poorly differentiated adenocarcinoma of the Japanese histological classification. The frequency of EBV-associated gastric carcinomas was 1.3% (2/150), and was the lowest ever reported in the world. We examined genotypes of two EBV strains detected from gastric carcinomas. Four different regions of EBV genome were examined by PCR-RFLP, coupled with Southern blot hybridization. The EBV genotype of the first case were type A, wild-type F at BamHI-F region, type D of BamHI-I region and the kept type of the XhoI cleavage site in LMP1. The second case had EBV whose genotypes were type A, wild-type F at BamHI-F region, and the kept type of the XhoI cleavage site in LMP1. The BamHI-I region of this case could not be analyzed.

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