Most genes in cancer family syndromes such as BRCA1 and BRCA2 are tumor suppressor genes. We can conclude that patients inheriting a cancer family syndrome will have a disproportionate loss of life because of early onset of cancer. They are associated with an autosomal dominant inheritance and are highly penetrant. Large genes with over 200 known mutations are already described. Different mutations will confer different risks of breast cancer, ovarian cancer, and other cancers.
Different mutations confer different likelihoods of tumor types and age of onset.
Even the same mutations in the BRCA genes confer different risks on different patient populations. Potential drawbacks to genetic testing include job discrimination, loss of insurance, and misinterpretation of results leading to unnecessary anxiety or false sense of security. In preparing a patient for testing, the usefulness of the genetic information must be determined before obtaining it. If there is no clear benefit to the patient, she may elect to defer testing or to cryopreserve DNA for potential future use of family members. All patients are screened beginning at 25 years of age or at 10 years earlier than the age of an affected relative.