We present a case of malignant melanoma arising in a longstanding melanocytic nevus on the palm. Histological examination showed mature nevoid cell nests in the dermis underlying atypical melanocytic lesion. Along the dermoepidermal junction spindle-shaped atypical melanocytes with dermal invasion are observed as well as pagetoid spreading of cells with clear cytoplasm or of spindle cells upward the epidermis. Subtypes of this case is difficult to conclude, because this case shares both histopathologic characteristics of superficial spreading melanoma and those of acral lentiginous melanoma. (Korean J Dermatol 2001;39(10): 1169~1172)