[Clinical and histopathological observations of pigmented spots on the feet]

Malignant melanomas, originating in the foot are said to have a higher frequency in Japan compared to Western countries, accounting for almost one third of all cutaneous malignant melanomas. In this context, pigmented spots on the feet which can be thought of as precursor lesions of malignant melanomas attract a great deal of attention from clinical dermatologists. In this study, 159 pigmented spots, consisting of 110 on the soles as well as 49 on the dorsal lesion have been studied clinically and histopathologically to clarify their relationship with the development of malignant melanomas. The results were as follows: 1) Junction nevi were most commonly observed at both sites. 2) Lesions tended to be darker in color and bigger in size as they proceeded from the simple lentigo to the junctional and compound nevi. 3) Most of the lesions were flat, but the elevated lesions were seen more frequently in the compound nevi and intradermal nevi which contained more dermal components. Also, lesions on the soles appeared to be more elevated. 4) Among the 21 cases which showed some cutaneous change, one case showed histopathological evidence of a premalignant lesion. 5) In the pigmented spots on the feet, the initial signs of premalignant transformation were skin elevation, more pronounced spot growth, measuring up to 5 mm in diameter, and dark black coloring (pigmentation). Therefore preventive excision of the lesion is recommended in cases where any of the three above features are in evidence.