Dysplastic nevi and the dysplastic nevus syndrome.

Patients with all the clinical features of FDNS but no family history of multiple abnormal nevi or melanoma can be compared with patients with neurofibromatosis due to a spontaneous mutation of the gene in utero. Whether or not such patients are in fact genetically identical to patients with FDNS and share their high risk of malignant melanoma remains to be determined. An isolated dysplastic nevus alone is not an adequate definition of SDNS, because current data are insufficient to show that its presence correlates with a uniquely high risk of melanoma when compared with other known risk factors. Until more specific tests for the FDNS gene become available, the diagnosis of SDNS must be made on the basis of close clinical and histopathologic resemblance to FDNS. Patients who present as adults with one or a few dysplastic nevi are best not labeled as having SDNS, because that label implies a genetic identity with FDNS that is probably not true and that deflects attention from other risk factors that are at least as important in estimating individual risks of developing melanoma.