DOI: 10.1097/01.scs.0000180487.65784.a1
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PMID: 16192874
Issn Print: 1049-2275
Publication Date: 2005/09/01
Potential for Development of Malignant Melanoma with Congenital Melanocytic Nevi
Justin Yovino; Seth Thaller
Excerpt
Congenital melanocytic nevi (CMN) that are present at birth have an incidence of approximately 1%. Fortunately, most are smaller than 1.5 cm in diameter and are classified as small (Fig 1).1 Remaining nevi range between 1.5 cm and 19.9 cm in diameter to be classified as medium and larger than 20 cm to be classified as giant (Fig 2).2 As diameter increases, the potential for malignant transformation follows. Small to medium congenital nevi rarely develop into melanoma before puberty. However, small to medium CMN-associated melanoma have a bimodal age distribution. Malignant transformation usually can be found originating around the periphery of a relatively flat CMN.3 Giant congenital nevi occur in less than 0.005% of live births, and the estimated incidence of malignant melanoma transformation has been reported to be as high as 10%. Additional concern is that 50% of congenital nevi-associated melanomas are detected by the age of 5 years, and the mortality has been reported as high as 40%.1
Although CMN can develop anywhere on the body, the most common locations remain axial (posterior trunk, head, neck, buttocks) followed by the extremities.1,3 The larger lesions are associated with irregular borders, color variations, surface irregularities, and boarder indistinctness.2 Risk factors for melanoma transformation include posterior midline location, greater than 20 cm in diameter, neural involvement, and to a lesser degree pigment regression of the nevi.
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