Women with a certain type of noncancerous lesion in the breast, called a radial scar, are more likely to develop cancer where the scars are found. Because the breast is extremely vulnerable to the effects of radiation, previous exposure to radiation increases the odds of breast cancer, especially for women exposed before the age of 30. Exposure as a young girl is a particular cause for worry. All breast cancer results from changes in genes, but not all changes in the genes are inherited. In fact, only about 5 to 10 percent of breast cancers are thought to be caused by inheritance.
Scientists have identified some of the genetic alterations, or mutations, that are responsible.
Statistics indicate that about 50 to 60 percent of women with a mutation in either gene will develop breast cancer by the age of 70. These mutations also increase a woman's risk of ovarian cancer, and possibly of colon cancer. And they tend to promote development of breast cancer at a younger than average age. Likewise, abnormalities in the p53 tumor suppressor gene can increase a woman's risk. There's also some evidence that women of Ashkenazi Jewish descent may be at higher risk of carrying a genetic mutation associated with breast cancer.