ABC of clinical genetics. Genetics of cancer.

Pigmentation of lips in Peutz-Jeghers syndrome. Development of cancer is related to both environmental carcinogens and genetic predisposition. Though the risk of a common cancer occurring in relatives ofan affected person is generally low, familial aggregations that cannot be explained by environmental factors alone exist in some O neoplasms, such as breast and ovarian cancers and melanomas. In occasional families a predisposition to a combination ofcommon cancers is