Identification of EBV, HPV and MMTV viruses, either as an individual or a multiple virus, by standard PCR in 50 fresh frozen breast cancer specimens (45 invasive ductal carcinomas and 5 invasive lobular carcinomas) and epithelial cells from 40 fresh normal breast milk specimens.

The prevalence of EBV, HPV and MMTV sequences is significantly higher in breast cancer as compared to normal specimens. The proportion of specimens in which no viruses were identified is significantly higher in normal breast specimens than in breast cancer specimens.