Mutation and cancer in man.

The risk of cancer can be increased by both genetic predisposition and environmental exposure. A common mechanism, mutation, may be involved in both. The rate of mutation in germ cells is the principal determinant of the incidence of genetically predisposed individuals, whereas the rate in somatic cells is the principal determinant in those not so predisposed. Many environmental carcinogens produce their effects via increased somatic mutation rates. The individuals of a population may be classified according to the operation of genetic predisposition, exposure to environmental carcinogens (mutagens), both, or neither. This last group reflects "background" somatic mutation rates.