IN-SITU DETECTION OF EPSTEIN-BARR-VIRUS IN GASTRIC AND COLORECTAL ADENOCARCINOMAS

The association of Epstein-Barr virus (EBV) with lymphoepithelioma-lik e carcinoma in the nasopharynx, which is common in Chinese from the so uthern region, is well established. Recently, EBV has also been found to be associated with lymphoepithelioma-like carcinomas (LELCs) and ca rcinomas with prominent lymphoid infiltrates in the stomach. We invest igated for the presence of EBV in 74 cases of gastric adenocarcinoma a nd 36 cases of colorectal adenocarcinoma from Chinese patients by in s itu hybridization (ISH) using an antisense EBER probe. In seven cases (9.5%) of gastric carcinoma, EBER was highly expressed in the adenocar cinoma cells and metastatic tumor cells in regional lymph nodes. In al l these cases, the normal gastric epithelium was EBV negative. None of the colorectal carcinomas showed a positive signal. Isolated positive lymphoid cells were frequently found in both tumors. Of the seven pos itive cases, only one was LELC, and the others were conventional adeno carcinomas of the intestinal type. Five showed expression of the viral RNA in all tumor cells as well as the surrounding dysplastic epitheli um. Interestingly, the sixth case showed distinct negative islands of dysplastic glands adjacent to strongly positive dysplastic glands and invasive carcinoma cells. This pattern of positivity, together with ne gative normal gastric epithelium and positive metastatic tumor, sugges ted that EBV infection occurred in the dysplastic phase and that an ap parent growth advantage was conferred by the EBV infection.