Is subungual melanoma related to trauma?

Subungual melanomas represent approximately 20% in dark-skinned and oriental populations compared to about 2% of cutaneous melanomas in white populations. UV exposure seems to be an important risk factor for cutaneous melanoma. However, UV radiation is unlikely to penetrate the nail plate. Another pathogenetic factor of subungual melanoma will be discussed. 406 subungual melanomas of the hands (n = 240) and feet (n = 166) of 74 patients from the melanoma registry of the Department of Dermatology, University of Tübingen, and of 332 patients from the literature were evaluated. The hypothesis of a uniform distribution of the occurrence of subungual melanoma on the fingers and toes had to be rejected (p < 0.001 using the chi(2)(4,0.95) test). There was a considerable predominance of subungual melanoma localized on the thumb (58% of all fingers) and the hallux (86% of all toes). Many patients report direct trauma related to the onset of subungual melanoma. This might be explained by coincidence, increased attention to a dark area under the nail, traumatic bleeding of a subclinical subungual melanoma or mutation of melanocytes during trauma-induced proliferation. Squamous cell carcinoma is known to occur in sites of chronic trauma. Trauma could be an etiologic factor in subungual melanoma as well.