ABCDE: how to check a mole for melanoma

Most moles are harmless, and the ones you've had since childhood almost never cause trouble. Even so, roughly one in every hundred adults will develop melanoma at some point in their life, and the earlier it is caught, the better the odds of a full recovery. The ABCDE method is a simple five-step check developed by dermatologists to help you notice the warning signs early. It is also the same framework Dermo is built on when it looks at the photos you take.

A is for asymmetry

Most normal moles are roughly symmetrical. If you drew a line down the middle of a typical mole, the two halves would look fairly similar. A suspicious mole often looks lopsided, as though the two halves don't quite match. When you check a spot, try to imagine splitting it down the middle and ask yourself whether one side looks clearly different from the other.

B is for border

A healthy mole has a smooth, even edge. Melanomas tend to have borders that are ragged, notched, or blurred, almost as if the colour is leaking outward into the surrounding skin. If the outline looks jagged or fuzzy when you look at it in good light, that's worth paying attention to.

C is for colour

Ordinary moles are usually a single uniform shade of brown. A concerning spot might have several colours mixed together, such as light brown, dark brown, and black all in one mole. Red, white, or blue patches inside a mole are particularly unusual and should be checked by a dermatologist.

D is for diameter

Most benign moles are smaller than six millimetres across, roughly the size of a pencil eraser. That doesn't mean every larger mole is dangerous, and plenty of perfectly harmless moles grow slightly bigger than that. Even so, six millimetres is a useful reference point, especially if a mole has been growing larger over time.

E is for evolution

This is the most important point of all. Any mole that changes noticeably over weeks or months, whether in size, shape, colour, or texture, deserves a closer look. A mole that starts itching, bleeding, or becoming painful is also a change worth taking seriously, even if its appearance hasn't shifted obviously.

When to see a doctor

If you notice two or more of the ABCDE signs in the same mole, or if a spot is genuinely changing and you don't have an explanation for it, you should book an appointment with a dermatologist. In Norway, you can contact your GP (fastlege) first, who will refer you on if it's needed. You don't need to wait until something looks obviously wrong, and if you're in any doubt, it's always better to have a professional look at it.

How Dermo uses ABCDE

ABCDE is one of several clinical frameworks Dermo is built on when a pigmented spot is being assessed. Rather than running it as a standalone checklist with a single score, the app brings these criteria into a wider assessment, where three independent AI models look at morphology, colour, borders, symmetry, and evolution, and then compare notes to reach a shared conclusion. The result is an assessment in plain language, grounded in the same principles a dermatologist would use, and meant as a starting point for a conversation with your doctor, not a replacement for it.

The limits of self-checking

ABCDE is a good first filter, but it isn't perfect. Some melanomas are small, symmetrical, or uniformly coloured, particularly in their early stages, and they can pass an informal check without raising any flags. The same is true for amelanotic melanoma, which lacks the dark pigment most people associate with dangerous moles. If something feels off even when the spot looks fine, trust that feeling and get it checked.