Genetic evaluation of cancer: the importance of family history.

Although the etiology of most cancers is thought to be sporadic and multifactorial, 5% to 10% of breast, ovarian, and colon cancers result from defects or mutations in specific genes inherited by a person through the germline. Distinctions may be made between hereditary and sporadic cancers. Because the risk of developing cancer is greater for persons from a hereditary cancer family than for the general public, these people should be considered for early detection and prevention options. Testing for selected cancer genes is available commercially, and physicians must determine which patients are appropriate candidates for these tests. Risk-reduction strategies and options for high-risk patients as well as legal and ethical issues pertaining to genetic counseling and testing will be considered.