Women who have a first-degree relative (mother, sister, or daughter) with breast cancer have double the risk of developing breast cancer. And having two first-degree relatives gives her five times the risk of someone with no family history of the disease.

Statistics can be confusing, though; while 20 to 30 percent of women with breast cancer have a family member with the disease, 70 to 80 percent of those with breast cancer had no family history to alert them.

A genetic history of the disease is also important. Studies show that between 5 and 10 percent of breast cancer cases are hereditary. Those women with BRCA1 and BRCA2 gene mutations, which seem to run in families, have an 80 percent chance of getting breast cancer during their lifetime.

Jews of Eastern European descent are most likely to carry the BRCA mutations, but they also occur in women from Hispanic, African American, and European origins. A number of less well-known genes, including the ATM, CHEK2, and p53 genes, also increase the risk of breast cancer.