Inheritance of cancer.

Extract: A single inherited mutant gene may be enough to cause a very high cancer risk. Single-mutation cases have provided much insight into the genetic basis of carcinogenesis, but they are relatively rare and account for only a small fraction of all cancers. Examples include mutation to the APC gene, causing early onset colon cancer in the syndrome familial adenomatous polyposis (tumorous polyp-tissue in the colon); mutation to either the BRCA1 or BRCA2 genes, causing an increased risk of breast cancer; and mutation to the TP53 gene, causing Li-Fraumeni syndrome with various early onset cancers such as bone or soft tissue sarcoma. Cancers sometimes cluster in families, but do not follow the rigid inheritance pattern characteristic of a mutation to a single gene. Males with a brother or father who has suffered prostate cancer are more likely to develop the disease. Similarly, females with a sister or mother who has suffered breast cancer are more likely to get a breast tumor. Some of the clustering may arise from the common diet and environment shared by families. Recently, however, researchers have begun to assign a significant fraction of cancer risk to the particular genetic variants that individuals inherit.