Possible related risks to breastfeeding.

Animal studies have identified a mouse mammary tumor agent transmitted through lactation that increases the incidence and reduces the age for tumor development in offspring. A similar viral particle has been detected with greater frequency in the milk of humans with a family history of breast carcinoma than in the milk of those with no history. Animal studies also indicate that a male offspring who has been breastfed, at low risk himself, could possibly transmit the agent through seminal fluid. The health team is encouraged to consider these factors when discussing infant feeding methods with women who have a positive family history of breast carcinoma.