A number of genes linked to cancer predisposition have been discovered in recent decades. Some of them create autosomal dominant monogenic cancer predisposition syndromes, which are extremely rare. The higher cancer incidence is attributable to a complex aetiology in the majority of families, with a number of lower penetrance cancer predisposition genes interacting with environmental variables. Genetic testing, enhanced surveillance, preventive surgery, and chemoprophylaxis may be recommended for persons at elevated risk of cancer due to a family history of cancer. . The difficulties underlying cancer genetic predisposition are examined in this article by looking at two common cancers: colorectal and breast cancer. Although the genetic nature of cancer has been known for over a century, the inherited features of cancer susceptibility have just recently become more fully defined. Compared to only a small minority twenty years ago, nearly half of all referrals to genetics centres are now for cancer susceptibility testing. Families with numerous individuals affected by a rare disease, sometimes accompanied by other phenotypic anomalies, have been the focus of studies on familial aspects of cancer.
