Genetic epidemiology: a powerful approach for the comprehension of cancer etiology.

Cancer is due to a damage at DNA level, either in the germline cells (in which case it is hereditary) or in the somatic cells, caused by gene mutations, spontaneous or due to environmental exposures. While epidemiologists have traditionally focused their attention on environmental risk factors, and geneticists have been mainly interested in rare hereditary cancers, the aim of genetic epidemiology is to look simultaneously at biological inherited susceptibility and environmental risk factors, with particular attention to possible gene-environmental interactions in the pathogenesis of the disease. Epidemiological approaches, in which target groups are populations or families, are briefly discussed in relation to their use, in the design of the studies, of genetic traits, measured either at DNA level or by gene products (proteins, enzymes, antigens).