The malignant potential of small congenital nevocellular nevi. An estimate of association based on a histologic study of 234 primary cutaneous melanomas.

In order to assess a relationship between small congenital nevocellular nevi and cutaneous melanoma, histologic features commonly associated with congenital nevi were sought in 234 melanomas. The detection of one or more histologic features of congenital nevi in 8.1% (19/234) of melanoma specimens was directly related to the number of slides and tissue sections with melanoma available for review, the predominance of superficial spreading melanoma (SSM) and the historic relationship to a preexisting pigmented nevus at the tumor site. The histologic association was inversely related to melanoma thickness and tumor location on the lower extremities. The observed frequency of histologic association was estimated to be approximately 4,000 to 13,000 times greater than expected on the basis of surface area by chance alone. These findings suggest that small congenital nevi may be precursors for at least some cases of cutaneous melanoma. The strength of histologic association is highly dependent on the specificity of methods used for detecting congenital nevi in melanoma specimens.