[Dysplastic nevi and the risk of melanoma: a guideline for patient care. Nederlandse Melanoom Werkgroep van de Vereniging voor Integrale Kankercentra].

Consensus was recently reached in the Netherlands regarding the clinical management of dysplastic naevi and the definitions in clinical and pathological diagnostics. The term 'dysplastic' is reserved for histological diagnostics; the term preferred for clinical use is 'clinically atypical naevus'. A naevus is defined as clinically atypical if it meets three of the following five criteria: > or = 5 mm in diameter, vaguely bordered, asymmetrically shaped, irregularly pigmented and a red hue (erythema). Presence of clinically atypical naevi is a main risk factor for melanoma. Dysplastic naevus syndrome (DNS) is present if a patient has a melanoma and one or several clinically atypical naevi. The diagnosis of 'familial DNS' (familial atypical multiple mole-melanoma syndrome, abbreviation FAMMM syndrome) is made if at least two close relatives (including the patient) are known with a melanoma with or without atypical naevi, while one or several (other) relatives have atypical naevi. The risk of melanoma in a gene carrier of familial DNS is close to 100%, while multiple melanomas develop in 30% of the gene carriers. No DNA diagnostics is yet possible in most DNS/FAMMM families, because of the involvement of genes yet unknown. Accordingly, at present it is still too early for DNA diagnostics. Currently, therefore, the diagnosis is based only on anamnestic, clinical and histological grounds.