Congenital melanocytic naevi and cutaneous melanoma.

Cutaneous melanoma is malignancy with a rapidly increasing incidence and its relationship to congenital melanocytic naevi is unclear. The purpose of this study was to investigate the incidence of congenital melanocytic naevi and the occurrence of cutaneous melanomas in these naevi. We performed epidemiological studies of the Swedish Medical Birth Register and the Swedish Cancer Register, together with a pathohistological review of the cases with congenital melanocytic naevi and cutaneous melanoma. Between the years 1973 and 1993, 3922 congenital melanocytic naevi were registered among 2 198 619 newborns, giving an incidence of 0.2%. Of all the congenital melanocytic naevi registered during the years 1973-1986, 7% were large (146 cases) and 93% were small; 1058 cases had a follow-up time of 15 years or more. Two cases may have been associated with cutaneous melanoma, but pathohistological review revealed no such association. The conclusions are that the incidence of congenital melanocytic naevi is low. We found no relation to cutaneous melanoma, but this could possibly be affected by the removal rate and the length of the follow-up period. Nevertheless, our study does not support the prophylactic removal of all congenital melanocytic naevi and there is no reason to believe that they play a part in the increasing incidence of cutaneous melanoma.