Acral lentiginous melanoma and its precursor--heterogeneity of palmo-plantar melanomas.

Malignant melanomas occur with high frequency in the volar skin and with heterogeneity consisting of acral lentiginous melanoma (ALM) and nodular melanoma in Japan. Analytical study has revealed the precursor of ALM which we designate plantar or palmar premalignant melanosis (PPM), and whose cellular characteristics appear to be similar to those of pagetoid premalignant melanosis or the radial phase of superficial spreading melanoma (SSM).