Kittler algporithm vs pigmented lesion on leg
This solitary pigmented lesion on an adult white shin caused concern.
The lower leg is one of the more common sites for melanoma, especially n the front which tends to get more sun exposure. This is mildly irregular and over 6mm so is concerning on the ABCD rule
So let’s view the dermoscopy.
Is it chaotic? (Kittler says chaotic means more than one colour or more than one pattern.) I think it’s mildly chaotic, maybe about 4 on a scale of 0-10 where 0 is perfect symmetry and 10 is absolute chaos (like the melanoma at the bottom of the post).
Kittler asks ‘If chaotic, it is a seborrhoeic keratosis?-look for clues.’
What clues can we see? I see lots of small white scaly clods which amount to surface keratin. That limits the diagnostic possibilities. There are also yellowy brown clods which are suggestive of seborrhoeic keratosis. There are no clues to BCC, haemangioma, dermatofibroma or melanocytic lesion.
We can therefore safely conclude that the lesion, although an ugly duckling, failing elements of the ABCD rule and mildly chaotic on dermoscopy, is a harmless seb k. The patient can be reassured and advised.
This portion of a larger melanoma is included for contrast as an example of strong chaos, at least 7 out of 10. (not that there is an agreed standardised measure of chaos!). It shows multiple colours and multiple structures including blue white veil, irregular dots and globules, asymmetric black blotch and inverse network.