Epstein-Barr virus-associated gastric carcinoma in Brazil: comparison between in situ hybridization and polymerase chain reaction detection.

Epstein-Barr virus (EBV) has been associated with 10% of gastric carcinomas. The aim of this study was to determine the frequency of EBV in gastric carcinomas in Brazil assessed by in situ hybridization (ISH) and PCR, which would contribute to the characterization of the clinical and pathological aspects of EBV-associated gastric carcinomas. One hundred and ninety-two gastric carcinoma cases were collected at hospitals in two Brazilian states. Seventy-three out of 151 cases were PCR(+), while 11/160 cases were ISH(+). Nine out of eleven ISH(+) cases displayed a diffuse staining pattern and 2 out of 11 a focal pattern. Both techniques showed that the EBV(+) cases were characterized by their association with males, older patients, lower gastric region, intestinal type, advanced stage and poorly to moderately differentiated tumors. The concordance between the two techniques was 55.8% (Cohen's kappa index = 0.034). Four cases were ISH(+)/PCR(-), while 49 cases were PCR(+)/ISH(-). Only two cases showed stained lymphocytes by ISH and one of them was PCR(-). The observed discrepancy between the two techniques could not be explained just by the elevated accuracy of PCR. ISH(+)/PCR(-) carcinomas may be encountered if EBV is not present in the whole tumor tissue or if there are polymorphisms in the sequences of the viral genome amplified. On the other hand, the high frequency of PCR(+) results associated with the absence of ISH staining in lymphocytes and/or tumors cells suggests that the virus may be present in tumor cells or other cell types without expressing EBER1, the target of the ISH technique.