Molecular diagnosis of Epstein-Barr virus in paraffin-embedded tissues of tumors with abundant lymphoid infiltration.

To evaluate the significance of Epstein-Barr virus (EBV) infection in tumorogenesis, we examined ten archival samples of acinic cell carcinomas of salivary glands with lymphoid-rich stroma, four archival samples of lymphoepithelioma-like carcinomas (LELC) of the urinary bladder, ten samples of oncocytic papillary carcinoma of the thyroid (Warthin-like tumors) and one sample of lymphoepithelioma-like carcinoma of the cervix, together 25 paraffin-embedded tumor tissues. Polymerase chain reaction (PCR) and in situ hybridization (ISH) assays were used. The EBV genome was detected by PCR using primers targeting the IR region. ISH was performed using EBER oligonucleotide probes. Each examination was repeated two times. Positive PCR result was obtained in 12% of samples only. However, this result was not confirmed by the subsequent second PCR examination. ISH revealed negative signals in all samples. Our results demonstrate the importance of the diagnostic strategy based on combination at least two independent methods. PCR due to its sensitivity may produce false positive results depending on the degree of infiltration the tumor sample by EBV carrying lymphocytes.