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March 23, 2011 / molehunter

Another harmless mole

The presence of hairs growing through a lesion is no guarantee of benignity, but is mildly supportive. The primary dermoscopic feature of this benign melanocytic naevus is uniformity. The edges are smooth and clean with no abrupt features, and scattered through the lesion if you look methodically are short curvilinear (comma) vessels, for example at 1, 7 and 9 o’clock just in from the edge. When you get used to seeing them, these vessels are very supportive of the diagnosis of a benign intradermal naevus as opposed to a BCC, which can look a bit similar macroscopically especially on the face.

There are several tiny milia like cysts on the left, the most noticeable one is near the periphery at 11 ‘ clock. Its worth noting that although these features are very typical of seborrhoeic warts, especially when multiple, they are also seen in other lesions. Dermoscopic evaluation of a lesion is usually a balancing act and deals in probabilities rather than certainties. Usually. That’s why patients should always be advised about the signs of change to look out for and report if they occur.

The beginner in dermoscopy is encouraged to examine very large numbers of bland, unchanging naevi about which there are no concerns in order to build up a mental picture of the range of normality. Of course, in most such naevi there can be no histological proof of benignity since it is unethical to excise naevi where there is no suspicion of danger. Guiseppe Argenziano, arguably world number one in dermoscopy, says this is OK and I agree. This lesion is benign despite the lack of histological confirmation! It is benign because I say it is, I know it is, and because it is! Seriously, whenever you reassure a patient, advise them what changes to look out for and come back about. You can only ever say ‘it looks harmless TODAY’.

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