How often are breast and ovarian cancers hereditary?
About 5 to 10 percent of breast cancers are hereditary. In these cases, breast cancer runs in the family. Similarly, 5 to 10 percent of ovarian cancer is hereditary. Hereditary cancer occurs because of a change in genes that is passed down to children. Some genetic changes cause an increased risk of cancer. In families passing an inherited change in a gene, multiple family members get the same type of cancer.
