All breast cancer results from multiple gene mutations. The initial mutation can be inherited from one's parents (familial breast cancer) or occur after conception (sporadic breast cancer). Inherited gene mutations play a role in about twenty-seven percent of all cases of breast cancer. Mutations in the genes BRCA1 and BRCA2 have been associated with early breast cancer in some families. But these families are rare and are thought to account for only about four percent of all breast cancer cases. Most inherited breast cancer risk results from the interaction of several mutated genes. Families with this pattern of inheritance will contain only a few members with breast cancer. These mutated genes by themselves are associated with only a small increase in breast cancer risk, but when several of these genes are inherited together they can lead to a significant increase in breast cancer risk. Diet and lifestyle may modify inherited breast cancer risk but more study is needed to identify and understand how this happens.