ABCDE: How to check a mole for melanoma

Most moles are harmless, and the ones you have had since childhood almost never cause trouble. But 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-point check developed by dermatologists to help you notice the warning signs early, and it is the same framework Dermo uses on the photos you send it.

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 do not quite match. When you check a spot, try to imagine splitting it down the middle and ask yourself whether one side looks different from the other.

B is for border

A healthy mole has a smooth, even edge. Melanoma tends 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 under good lighting, that is worth paying attention to.

C is for colour

Ordinary moles are usually a single uniform shade of brown. A concerning spot might have multiple colours mixed together, for example light brown and 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, which is about the size of a pencil eraser. That does not mean every larger mole is dangerous, and plenty of perfectly harmless moles grow slightly bigger than that. But 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 criterion 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 has not obviously shifted.

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 do not have an explanation for it, book an appointment with a dermatologist. In Norway you can contact your fastlege (your regular GP) first, who will refer you on if they think it is needed. You do not need to wait for something to look obviously wrong. If you are uncertain, it is always better to have a professional take a look.

How Dermo uses ABCDE

ABCDE is one of several clinical frameworks Dermo's AI has been trained to think through when it examines a pigmented lesion. Rather than running it as a separate checklist with a single score, the app weaves these criteria into a broader reasoning process where three AI specialists independently evaluate morphology, colour, borders, symmetry, and evolution — and then compare notes to reach a consensus. The result is a plain-language assessment grounded in the same principles a dermatologist would use, meant as a starting point for a conversation with a doctor, not a replacement for one.

The limits of self-checking

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