Subungual malignant melanoma: clinicopathological features of 100 cases.

From the files of the Scottish Melanoma Group, we have identified 100 cases of subungual malignant melanoma (melanoma arising in the nailbed), and this represents 2.8% of the total melanomas registered during the period 1979-1989. Almost equal numbers arose on the foot as on the hand, with the thumb and big toe as the commonest digit affected. More than 80% were greater than 1.5 mm, with the mean Breslow depth 4.7 mm, and 70% were Clark level IV or V. Approximately half of the cases were of acral lentiginous type. At 5-year follow-up (54 cases), 26 have died of melanoma, six have died of an unrelated disease, four are alive with recurrence and 18 are alive and well. Features related to clinical outcome at 3 years were Breslow depth, mitotic count and the presence of vascular invasion.