Which mole changes should worry you

The vast majority of moles are benign and never cause problems. But melanoma, the most dangerous skin cancer, can start either as a new mole or as a change in an old one. Caught early, it is much easier to treat. That is why it is important to know how to look at a mole.

The ABCDE rule

• A, asymmetry: one half of the mole does not match the other
• B, border: the edges are ragged, notched or blurred
• C, colour: there are several shades and the colour is uneven
• D, diameter: larger than 6 millimetres
• E, evolution: size, shape, colour or sensation is changing

The most important letter is E. A changing mole always needs attention, even without the other signs.

The "ugly duckling" sign

A person’s moles usually look alike. A mole that stands out from the rest in size, colour or shape, the "ugly duckling", should be assessed separately.

The 7-point checklist

In this checklist used by doctors, three major signs (change in size, shape or colour) score 2 points and four minor signs (diameter of 7 millimetres or more, inflammation, oozing or crusting, change in sensation) score 1 point. A total of 3 or more means the mole should be shown to a dermatologist promptly. A study testing the checklist in general practice showed that it helps to pick out suspicious moles. You can answer these questions yourself in the test on this site.

What dermoscopy adds

A dermatoscope shows the inner structure of a mole. Systematic reviews show that, in experienced hands, dermoscopy is more accurate for detecting melanoma than looking with the naked eye alone. That is why I always examine a suspicious mole with a dermatoscope and, if needed, monitor it or suggest removing it for histology.