What is the differential of this new solitary lesion on the arm?
Dermoscopy - Introduction, Terminology and Structures
A document to help you understand the dermoscopic descriptions used in this blog.
Dermoscopy Algorithm
To help you work through dermoscopic cases.
Clinically the differential would have to include a seborrhoeic keratosis. Dermoscopically you could think about an angioma, but let us work our way logically through this case using the algorithm.
1) There are no obvious features that this is melanocytic
2) Are there any definitive features that this is benign? Clinically the differential would include a SK, and dermoscopically an angioma, however, put this together and things do not add up ie clinically this does not look like an angioma, and dermoscopically it does not look like a SK, and why has it suddenly grown?
3) There is no suggestion this is a BCC
4) Moving along to the end of the algorithm this leaves a relatively structureless lesion meaning that we can no longer exclude a melanocytic lesion. Given that this is a growing nodule there is no option other than to excise this immediately. Another concern is that a variety of vessels can be seen, some of which are linear, which should not be seen in angiomas (in the black circle ... not easy to see).
Histology showed a nodular melanoma, Breslow thickness 1.2 mm.
The message here is that if we are faced with a structureless lesion that we can't diagnose clinically, we need to find out the diagnosis histologically. Some 50% of nodular melanomas are hypomelanotic.
Copied with kind permission from South Tees Foundation Trust.
