How to tell if a mole is cancerous?

How to tell if a mole is cancerous?

The most popular system for telling if a mole is cancerous is the ABCD system (see below or check out our more in-depth guide), but this is a late detection system and should only be used as a guide. If your moles show any signs of the following, then the skin cancer may already be advanced.

At the Skin Safe Clinic, we believe that Early Detection = Life Protection, so it’s important not to wait for the symptoms to visibly show before getting your moles checked by our experts.

Have a look at your mole and ask yourself: is it perfectly symmetrical around two axes or is it asymmetrical?


Are the borders of the mole quite smooth, or is it quite jagged? This may mean you might want to have it examined.


Is the colour the same throughout? This can be from light brown to dark brown. If one side or a part of the mole is much darker and almost black, compared to the rest of the mole, we advise you get it checked out.


The last thing to look for is if your mole is over 6mm across.

This is a nice conventional system that lets you diagnose that you may have a mole that is cancerous, but by the time you see these changes this is not an early Melanoma, it could be relatively advanced.

Remember: Melanoma can start at less than 6mm, well before it becomes asymmetrical, it may be perfectly symmetrical when it’s small, the irregularity doesn’t show until quite late and the colour distinction does not show until later either. We use a special instrument called a dermatoscope which allows us to look at the very early stages of a potentially cancerous mole and allows for early detection.

Look out for moles that have black in them
The problem with this system is that if you look at any of your moles, you’ll find that most of them fit these features so it can cause a lot of worry. The commonest thing we say to our patients is look out for the colour black. It’s easy to pick up and see compared with a regular mole which is typically brown in colour.

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