Most tumors appear to be sporadic. Once the human genome has been catalogued, it comes as a surprise that (as far as we know) the number of genes involved in cancer is small. Malignant growth is a relatively frequent occurrence and cancer incidence, especially in large families, is high, yet less than 10% of tumors are considered truly hereditary. Epidemiological studies have traditionally relied on the evaluation of family trees that are notoriously incomplete and the recorded causes of death dubious. Only recently, genetic epidemiology has helped to identify marked familial aggregation of cancer susceptibility genes and with segregation analysis, the presence of high-risk, low frequency alleles. The latter is being pursued in systematic studies of cancer risks in siblings and offspring from affected parents.
Go to Previous Page
Go to Next Page