Gastric cancer is the fourth leading cause of cancer-related death in the world. The identification of gastric cancer subtypes related to recognizable microbial agents may play a pivotal role in targeted prevention and treatment of this cancer. In the current study, the aim was to study the frequency of EBV infection in gastric cancers in Iran.

Paraffin blocks of 682 cases of various types of gastric cancer from Tehran, South and North area of Iran were collected. Twelve tissue microarray (TMA) blocks were constructed from these blocks. Localization of EBV in tumors was assessed by in situ hybridization for EBV-encoded RNA (EBER). Chi-squared test was used to evaluate statistical significance between EBV-associated gastric cancer and clinicopathologic tumor characteristics.

Fourteen out of 682 cases (2.1%) of gastric adenocarcinoma were EBER-positive. EBER was positive in 8 out of 22 (36.4%) of medullary carcinomas and 6 out of 660 (0.9%) of non-medullary type, which was a statistically significant difference (p<0.001). The EBV associated gastric cancers were more frequent in younger age (p = 0.009) and also showed a trend toward lower stage of tumor (p = 0.075).

EBV-associated gastric adenocarcinoma has a low prevalence in Iran. This finding can be due to epidemiologic differences in risk factors and exposures, the low number of gastric medullary carcinomas in the population. It may also be related to gastric tumor heterogeneity not detected in the TMA technique.