The ABCDEs of melanoma

Checking your own skin regularly is one of the simplest ways to catch skin cancer early. The ABCDE rule is a widely used guide to the features that can set melanoma apart from an ordinary mole.

A is for Asymmetry

If you drew a line through the middle of the mole, the two halves wouldn't match. Ordinary moles are usually round or oval and symmetrical.

B is for Border

The edges are irregular, ragged, notched or blurred, rather than smooth and well defined.

C is for Colour

The colour is uneven, with different shades of brown or black, or patches of red, white, grey or blue.

D is for Diameter

The mole is larger than about 6 mm across, roughly the size of a pencil eraser. Melanomas can be smaller than this, so size alone is not reassuring.

E is for Evolving

The mole is changing in size, shape, colour or height, or developing new symptoms such as itching, crusting or bleeding. Change is often the most important warning sign of all.

Two more signs to know

• The "ugly duckling" sign. Most of a person's moles tend to look alike. A mole that looks different from all the others deserves a closer look, even if it doesn't match the ABCDEs.
• Raised, firm and growing. Some melanomas (nodular melanoma) don't follow the ABCDE pattern. A spot that is raised, firm to the touch and growing over weeks should be checked promptly.

How to check your skin

Once a month, look over your whole body in good light, using a full-length mirror and a hand mirror for your back, scalp and the backs of your legs. Don't forget the soles of your feet, between your toes and under your nails. Taking photos on your phone can help you notice change.

Self-checks are useful, but some early changes are too subtle to see by eye. If you have many moles or other risk factors, mole mapping gives you a photographic baseline that makes comparison far more reliable.