ATYPICAL MELANOSIS OF THE FOOT - A REPORT OF 3 CASES IN JAPANESE POPULATIONS

Background: Acral lentiginous melanoma is the most common type of mali gnant melanoma in the Japanese population. In most instances, classic acral lentiginous melanoma or acral lentiginous melanoma in situ can b e readily distinguished from other benign pigmented lesions by virtue of its atypical clinical appearance. Observation: We present three cas es of seemingly malignant pigmented lesions on the foot, all arising i n Japanese females. Clinically, the lesions are characterized by irreg ular borders and variegated pigmentation closely mimicking those of ac ral lentiginous melanoma in situ. However, the histologic findings rev ealed only focal slight melanocytic hyperplasia with minimal cytologic atypia along the basal layer. Despite the malignant clinical features , thorough histologic examination failed to disclose any area with sig nificant melanocytic atypia or evidence of malignancy. Conclusions: To the best of our knowledge, similar lesions with the clinical appearan ce of melanoma in situ and completely lacking histologic evidence of m alignancy have not been reported. We, therefore, prefer to designate t hese lesions as atypical melanosis of the foot to highlight the clinic ally apparent atypical findings and to distinguish them from malignant melanoma in situ of the foot.