Fig. 17

Histopathologic features of advanced primary acral melanoma. Florid random proliferation of atypical melanocytes is detected not only in the epidermis but also in the dermis. Sheetlike dermal invasion is seen in the center of the lesion (a). The melanocytes proliferate as solitary units as well as in nests with variable shapes and sizes (b). Focally, solitary arranged melanocytes are prominent within the epidermis. The melanocytes are different from pagetoid cells commonly seen in SSM/low-CSD melanoma (c)