2 slightly odd looking moles on the back
This late middle aged white person was concerned about 2 moles on the back. They had been present for at least 10 years and there was no clear history of recent change or other worrying features.
There are several pigmented lesions here, of which the ones at 4, 6, 7 and 12 o’clock are obvious seborrhoiec keratoses. The 2 largest and darkest are apparently melanocytic naevi. Applying the ABCD rule, they are mildly ‘wrong’ being somewhat asymmetrical, of varied colour, over 6mm diameter, and the one at 9 o’clock has an irregular shape and edge. Dermoscope time. NB please remember to click on the image to magnify it.
These are in my opinion topographically very similar, so I will describe both together to start. Both are around 10 by 6 mm, main colour medium brown, reticular network and paler in the middle. We also see dots. As I always say about dots (and globules) when we see them we want to ask 3 questions.
1) are they similar in size?
2) are they similar in colour?
3) are they distributed in a homogenous manner?
These dots are small, even in size and colour, and distributed fairly evenly. This isn’t anything to worry about. We do worry if dots or globules are very irregular in size, colour and distribution.
Regarding the reticular network (lines and holes), the referring doctor was concerned that this network was irregular. I wasn’t. Of course it’s not perfectly regular, but then it never is. I have posted some examples of irregular network and will post some more, but in the end you have to make a judgment. I recommend using the dermoscope to look at thousands of moles about which there is no clinical suspicion to ‘get a feel’ for normal. Ask a colleague, photograph everything you excise and check back the histology, study as many on line images as you can, it all comes.
The fact that these 2 naevi are quite similar is reassuring. 2 primary melanomas in one patient is possible, but uncommon. If a patient has several naevi that are slightly odd but similar to each other, its most likely genetic and of no importance. Beware the ONE mole that stands out dramatically from the rest, the ‘ugly duckling’.
NB the first mole is quite irregular in shape and outline. OK, that gets our attention. But the dermoscopy shows that he colour and architecture are very homogenous. That is far more important than shape.
There are no globules, no streaks, no blue grey veil, no colours other than brown (i.e. no blue, grey, black or red) and taken with the clear history of both moles being present for 10 years plus and no recent change a 99% plus likelihood of benignity was justifiable.
However, it should be noted that some doctors would want to excise one or other of these moles to put the issue beyond doubt. All I can say is that I was clinically convinced they were both harmless, mildly atypical at worst. You can’t IMO justify the NHS cost, patient discomfort and scarring of very mildly atypical skin lesion excisions just to prove your point, nice as it would be to have histology for absolutely everything.
Diagnosis: benign compound naevi. No histology available as it was not considered necessary to excise. Photograph and review was advised, mainly for reassurance. As always, the patient was advised what changes to look out for and report.