Managing subungual melanoma in situ in general practice

This month, we look at subungual melanoma in situ. The issue of whether a pigmented finger or toe nail needs further evaluation, or biopsy, is a real challenge for most GPs. We simply don't see enough cases to develop any expertise in this type of case. Honestly, most skin cancer doctors also don't see enough cases to become confident, either.

In this paper, Ohn et al develop a predictive scoring model for dermoscopy of subungual melanoma in situ. Of course, the key challenge is to decide whether the lesion is benign or suspicious. Their model uses five characteristics: asymmetry, border fading, multicolour, width >3mm, and Hutchinson sign (extension of pigment to adjacent skin). Their model ranges from 0 to 8 points, and with a cut off value of 3 sensitivity is 89 per cent and specificity is 62 per cent.

How do we apply this in general practice? I think we need to go to an even more simple space here. My advice is, if the pigmentation is not obviously benign (one colour, narrow, not growing, no skin involvement) on a single digit, and is not new, then follow up is enough. Anything else needs expert review.

Professor David Wilkinson

Learn more about skin cancer in primary care in the Skin Cancer Certificate Courses: