00         Positive 1.56 0.72 3.37 0.26 Lymph node Negative 1.00         Positive 2.47 1.48 4.11 0.01 Stage I or II 1.00         III or IV 1.49 1.01 2.20 0.04 Discussion Gastric carcinoma is one of the most Cell Cycle inhibitor common cancers worldwide and the second most common cause of cancer-related death, with 876,000 new cases diagnosed annually [17]. In addition, EBV-positive gastric cancer cases make up the largest group of EBV-associated malignancies. Thus, defining the role of EBV in the carcinogenesis of this widespread malignancy is essential. Using in situ hybridization technique,

we examined 235 cases of primary gastric cancers, which to our knowledge was the largest study group of this type in the United States. Specific nuclear EBER1 transcripts were found only in gastric carcinoma cells. In contrast, EBV was detected in none of the normal or dysplastic epithelia in the EBVaGC or EBV-negative cases. Specifically, in 10 of check details the 12 cases of EBVaGCs, EBER1 was expressed in almost all carcinoma cells, suggesting that EBV infection occurs early in oncogenesis with a subsequent clonal expansion of EBV-containing tumor cells, significant findings which have also been reported by investigators using molecular genetic techniques [13, 25]. In

two cases of EBVaGC, EBER1 was expressed in a small number of gastric carcinoma cells, visualized with focal EBER1 staining, indicating that EBV infection occurs after neoplastic transformation has taken place. The EBV nuclear expression was restricted to gastric carcinoma cells. No expression was found in the presumed precursor lesions of gastric carcinoma. Our results stiripentol agree with those of other studies in which EBER transcripts were not detected in adjacent precursor lesions, such as intestinal metaplasia

[4, 26–28]. However, some studies have described the presence of EBV in dysplasia [3, 13], and others have detected the presence of EBV in intestinal metaplasia [14, 15]. There are several reasons for these discrepancies. First, dysplasia adjacent to carcinomas is difficult to distinguish from local carcinoma spread [17]. Secondly, variation in the techniques used and methods of interpretation can lead to inconsistent results. For example, one study that used both polymerase chain reaction and in situ hybridization indicated that the EBV genome was detected by polymerase chain reaction in one case of normal gastric mucosa, but not by in situ hybridization [19]. Recently, one study examining EBV in gastric carcinomas and gastric stump carcinomas and found that EBER1/2 transcripts were restricted to the carcinoma cells in both types of cases [12, 29]. The absence of EBER1 transcripts in preneoplastic gastric lesions (intestinal metaplasia and dysplasia) but their presence in two distinct types of gastric carcinoma further supports the theory that EBV can infect only neoplastic gastric cells.