Small congenital nevocellular nevi and the risk of cutaneous melanoma.

The relative risk of melanoma associated with small congenital nevi was estimated by comparing the published frequency of histologically documented nevocellular nevi in newborn infants with the frequency of: (1) congenital nevi at the tumor site, ascertained by history in 134 patients with melanoma; and (2) tumor-associated nevi with congenital features in 234 melanoma specimens. A 21-fold increase in melanoma risk was estimated for persons with small congenital nevi when nevi were ascertained by history, and a three- to tenfold increase in risk when nevi were ascertained by histology. Based on these approximations of relative risk from historic and histologic methods of detection, persons with small congenital nevi who live to age 60 are estimated to have cumulative risks for melanoma of 4.9/100 and 0.8 to 2.6/100, respectively. The increased risk is related presumably to the markedly increased probability of melanoma arising in association with small congenital nevi. In other words, small congenital nevi may represent precursors for at least some cases of cutaneous melanoma. The estimated risk are highly dependent on the specificity of methods used for ascertainment of congenital nevi.