Subungual melanoma. A clinicopathologic study of 16 Japanese cases.

Melanoma occurs much less frequently among Japanese than among white people. The occurrence of subungual melanoma is uncommon both among white and among Japanese people. However, the authors found 16 subungual melanomas among 86 cases of cutaneous melanoma (19%) at their clinic, quite a high incidence. Of these, 69% (11/16) occurred on the hands and 31% (5/16) on the feet. By far the most common site was the right thumb. Histologic examination revealed that 67% were characterized by acral lentiginous, 50% by superficial spreading, and that there were no nodular melanomas. Most were Clark's Level IV and V at the time of diagnosis. The 5-year survival rate for subungual melanoma was 40%. No statistically significant differences in rate were found between subungual melanoma and volar melanoma. The term "acral" melanoma is recommended to describe the melanomas in the acral regions, because it is descriptive of the regions directly affected.