Ugly duckling on the arm
This suspicious pigmented lesion was presented due to its outstanding nature. It was a genuine ‘ugly duckling’ and there was no other lesion on the skin anything like it, also a history of recent change in size and/or colour (people can’t always remember) so therefore fully deserving of evaluation.
Dermoscope time again. What would I do without it?
The sub-macroscopic view through the dermoscope shows multiple comedo like openings and milia like cysts. the very clean edge visible on naked eye view is confirmed. This can only be a seborrhoiec keratosis (aka basal cell papilloma, seborrhoiec wart) and therefore the patient can be confidently reassured. No treatment is necessary, but it is always wise to examine the rest of the skin in case there is something else to see. There was not.
The sharp angle at the top end of the lesion (second image) had been noted by the patient and was worth pointing out, but in this case it is completely random. Also of note, the amorphous hazy area in the centre of the lesion is NOT the dreaded blue/grey veil of melanoma. If you doubt me, I will post a few of those in the near future and indeed suggest a Google Image search on (blue grey veil + dermoscopy). Yes, many beginners worry about this appearance and it does have a few purely colour based similarities to a blue/grey veil, but it can’t be since we have established on positive grounds that this lesion is a seborrhoiec keratosis, without any positive features to identify a melanocytic lesion. Lots of seb ks have this hazy bluish amorphous appearance, but given the crisp edge and multiple comedo like openings and milia like cysts it can’t be anything else, so we discount the colour scheme. Interpret everything in context.
Incidentally, there are no features pointing to any other kind of lesion e.g. haemangioma, melanoma, BCC. So on positive grounds (features we see) and negative grounds (features which are absent) this is benign, although initially it looked worrying. This is what we sometimes call a sheep in wolf’s clothing!
The next case (sheep in wolf’s clothing) is the same thing on a different patient.