Mouse mammary tumor like virus sequences in breast milk from healthy lactating women.

Mouse mammary tumor virus (MMTV) has been a long standing candidate as a potential cause of some human breast cancers. Forty years ago, electron microscopic images of MMTV-like particles were identified in milk from 5% of healthy lactating women. These observations, however, have not been confirmed by modern methods.

Breastfeeding, breast milk and viruses.

Background: There is seemingly consistent and compelling evidence that there is no association between breastfeeding and breast cancer. An assumption follows that milk borne viruses cannot be associated with human breast cancer. We challenge this evidence because past breastfeeding studies did not determine "exposure" of newborn infants to colostrum and breast milk.