[Genetic counseling in oncology].

Some aspects of genetic counselling in cases with familial cancers is illustrated by use of 4 typical observations. By exact diagnosis and extended genealogic analysis the risk of consanguineous relatives may be estimated, if inheritance and genetic peculiarities of the particular disease are known. Predictive and presymptomatic testing should only be undertaken after thorough counselling. It should anyway be restricted to cases where preventive or curative measures are available.