The American Cancer Society reports that as many as 10 percent of breast cancer cases are thought to be caused by gene changes passed down through families.
Those changes, also known as mutations, can affect a number of genes, including the BRCA1 and BRCA2 genes, which both play a role in tumor suppression.
A women with a mutation in the BRCA1 or BRCA2 gene has up to a 70 in 100 chance of being diagnosed with breast cancer in her lifetime. Men with a mutation in BRCA1 or BRCA2 also are at greater risk of breast cancer, even though instances of the disease among men are rare.
Mutations in other genes, including the TP53, STK11, PTEN, CDH1, and NF1 genes, among others, also are associated with a higher risk for breast cancer.
Women with a family history of breast cancer, and particularly a first-degree relative like a mother, sister, or daughter who has had the disease, also are at greater risk for breast cancer compared to women with no such family connection.