Familial cancers

Although cancer is common in the general population, only a small proportion is thought to be due to highly penetrant cancer genes. Families with a highly penetrant cancer predisposing gene may be recognised by the presence of a high number of individuals within the family with a particular cancer type, or individuals with features associated with rare inherited cancers, such as retinal changes or multiple colonic polyps. It is likely that there are many other less penetrant genes, which, in combination with environmental influences, will confer a greater lifetime predisposition to cancers. These genes are currently being identified through epidemiological studies