Solitary small active junctional nevi in juvenile patients.

Solitary small very dark and papular pigmented nevi, less than 4 mm, are seen commonly in the second decade of life and have a distinctive histologic pattern. Microscopically these lesions show abundant intraepidermal melanin, included within the keratin layer, and proliferating single melanocytes or nevus cell nests. Prominent nucleoli in the melanocytic cells, occasional mitoses, and the invariable presence of moderate numbers of dermal melanophages and lymphocytes indicated the activity of the pathologic process. The benignity of the lesions in nine patients is supported by a benign course over a one- to three-year evaluation period after limited excisional biopsy procedures. The clinical and pathologic evidence of activity in these nevi suggests yet another possible precursor of malignant melanoma. The B-K mole syndrome and the dysplastic nevi syndrome differ from these cases both clinically and histologically.