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September 15, 2012 / molehunter

Contact and no-touch dermoscopy compared in benign raised naevus

This is a benign intradermal naevus (IDN) on the face. Diameter 7mm, very long standing, one of several lesions about which there was no concern. Papular and nodular basal cell cancers can sometimes mimic these harmless lesions, the most important clue is the duration. A BCC will usually have developed over 2 years or less, the IDN sometimes thirty years or more. Dermoscopy can help too. You are looking for different vessel patterns.

Now lets have a look at the same lesion with the cross polarising function of the Dermlite hybrid scope.

A benign intra dermal naevus viewed with the cross polarising no-touch scope. The view is different from what we see with the glass plate oil contact scope.

Note the meniscus of alcohol gel from the glass plate. The vessels are flattened. Some brown globules are visible.

DISCUSSION: the most important diagnostic feature is the long history and the presence of several other very similar lesions. A safe diagnosis of benign IDN could be made without the dermoscope. However sometimes there is uncertainty, for example there is nothing to prevent a 76 year old with 5 IDNs developing a BCC and it may be tricky to tell them apart. A BCC will have crisply focussed arborising vessels while an IDN as here has short, curved, less well focussed curvilinear or ‘comma’ vessels. Also the BCC vessels tend to taper along their length while the curvilinear vessels of the IDN are of more even, usually fatter,¬†calibre. Brown globules are a helpful finding also, tending to support a diagnosis of IDN-however you can see pigmented stuctures in BCCs, I have posted many on this blog.

Note the subtly different views with the different modes of dermoscopy. Sometimes one is better, sometimes the other. I like to have both, tending to use the faster less messy no-touch style for scanning many lesions and the glass plate gel contact for a closer look at ‘interesting’ lesions and for photography. I will return to this issue later with other examples.

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