About 35% of nodular and superficial spreading melanomas arise in a background of melanocytic nevi (congenital, acquired, or dysplastic). Small congenital or acquired nevi rarely develop into melanomas. However, giant congenital nevi have a 3-18% risk of malignant transformation. Lentigo maligna melanoma is not associated with pre-existing benign or dysplastic nevi. The image shows a benign nevus in the dermis and superficial spreading melanoma. Image copyright: pathorama.ch.