[Hereditary predispositions to cancer: the genetic diagnosis in practice]

Genetic consultations allow to identify families in which an hereditary predisposition to cancer is transmitted. In most cases the gene involved can be studied leading to identification of families members carrying or not the mutation conferring the cancer risk. In this case, cancer risk is more accurately explained and measures, adjusted to the risk, were proposed for early screening of the disease. Capacities to characterize an inherited mutation of the susceptibility gene vary according to our knowledge of the gene, its structure, its function, the kind of mutation(s) and also, the available techniques. The purpose of this paper is to describe the most frequently used techniques for direct or indirect molecular diagnosis of cancer predisposition and to specify, for each of them, the situations where its use seem the fittest. The example of breast cancer hereditary predisposition, where multiple susceptibility genes were identified and other are still unknown, illustrates the various degree of diagnosis that can be proposed and the strategy techniques used according to the gene.