Clinical and histopathologic characteristics of early lesions of subungual malignant melanoma.

Twenty-one Japanese cases of subungual malignant melanoma were investigated clinically and histologically. In the majority of the cases, the initial sign of the disease was confirmed to be melanonychia striata. Five cases of Clark's Level I melanoma were found in the series. Melanonychia striata had appeared as the initial sign in these five cases. Melanonychia striata is frequently observed in persons who are not white and is attributed to various local and systemic causes. Detailed clinical analysis of the five cases of early subungual melanoma showed that melanonychia striata with the following characteristics may increase the risk of early subungual melanoma developing: it is noticed during adulthood, it is broader than 6 mm, it is brownish with variegated shades or homogenously black, and it is accompanied by periungual pigmentation (Hutchinson's sign). Detection of early lesions of subungual melanoma is beneficial not only for the improvement of prognosis, but also for the preservation of the affected phalanx.