Epstein-Barr virus (EBV) is associated with human B cell lymphomas, but is also commonly found in the epithelial cells of undifferentiated nasopharyngeal carcinoma. As recent reports have also suggested a wider distribution particularly in lymphoepithelioma-like carcinomas, we investigated its presence in breast carcinomas of varying histology. Using PCR amplification of DNA extracted from paraffin sections, we found that EBV was present in 15/28 breast cancers. It seemed to be more prevalent in Paget's disease and in medullary carcinomas and less frequent in the invasive ductal cancers that constitute about 75% of breast carcinomas. This was confirmed by analysis of purified DNA extracted from a further 48 invasive ductal carcinomas: 19 were EBV positive. Latent membrane viral protein was detected by immunohistology in scattered epithelial tumour cells. The vast majority of lymphoid cells were unstained. A rough approximation indicates that there could be up to several hundred copies of the EBV genome per mu g of extracted tissue DNA. We were unable to demonstrate the presence of RNA by in situ hybridisation using fluorescein labeled EBER oligonucleotides but this may be due to technical reasons. No EBV DNA was found using PCR in the 12 normal breast specimens examined. These initial results suggest that the EBV genome is present in certain breast epithelial malignancies.

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