[Genetic counseling and DNA testing in patients with increased risks for malignant melanoma].

There are numerous risk factors for the development of malignant melanoma. It has been documented that genetic predisposition exists but exogenous factors are also very important. In familial melanomas it has been well established that mutation in the CDKN2A gene which is located at chromosome 9 leads to a marked risk for malignant melanoma. This tumor-suppressor gene is important for the regulation of the cell cycle and mutation in this gene is associated also with an increased rate of pancreas cancer. The penetrance of this mutation is influenced by UV-energy. In addition it has been shown that a second cluster for the familial atypical nevus syndrome is located at chromosome 1p36. Patients with the rare disease xeroderma pigmentosum have a defect in the DNA-repair mechanism inherited in an autosomal recessive trait and therefore develop within the first 20 years of life numerous malignant skin tumours including malignant melanomas. But also in non-syndromic patients a decrease of DNA-repair ability may occur. It has been shown recently that reduced DNA-repair ability is an independent risk factor for malignant melanoma and may contribute to susceptibility to sunlight-induced melanoma among the general population. Other constitutional risk factors for the development of malignant melanoma are fair skin, red hair and blue eyes. The most important exogenous risk factor is UV-exposition. Extensive and repetitive sunburns before the age of 15 years are especially predisposing to malignant melanoma. The most important preventive measures are continuous sun-protection including avoidance of sun in noon time on tropical and subtropical places, wearing a hut and sunglasses and application of sun-screens with high sun-protection factor. Furthermore a regular check for changing moles is indicated in persons with multiple atypical nevi or a familial melanoma syndrome. Nowadays molecular genetic screenings are available within research projects for members of melanoma-prone families. The controversy of such possibilities is discussed.