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Turning the light on moles

28 Mar 2003

Everyone has a mole or two. But what are they, where do they come from and can they be dangerous? We take a look.

Moles – known medically as naevi – are darkened patches of skin, which are nearly always brown in colour and usually found above the waist on sun-exposed parts of the body.

They come in a variety of shapes and sizes – large, small, raised, flat, and hairy or smooth. The only consistent thing about moles is that everyone has them – most people average between 10 and 40 on their body – and they are nearly always harmless.

Rise above, then fade away

Moles are actually made up of clusters of the skin cells that give you a tan – melanocytes. These cells exist everywhere in your skin and produce a pigment which causes the skin to darken when exposed to the sun.

It’s not known exactly why, but occasionally a large number of these melanocytes group together, producing a dark patch of skin on the body. As the body is exposed to sun over the years, they tend to grow, becoming larger in diameter or raised above the surface of the skin.

While some people are born with a few moles (congenital naevi), most appear while the body is developing. After the age of 20, new moles are uncommon. They also have a lifespan – albeit a long one. Over time, moles may flatten again, fade and become flesh coloured or simply disappear.

Some people are predisposed to moles – mostly fair-skinned people – and people who have them are more likely to have children with moles. Apart from that, exposure to sun is the most common cause of new ones appearing.

Down, down, deeper and down

But while moles are mostly harmless, they are a major cause for concern with regard to skin cancer. Consultant dermatologist at St Mary’s Hospital in London, Dr Sarah Wakelin, says moles are a risk factor, and melanoma – skin cancer that can spread to other parts of the body – is continuing to increase in the UK.

She explains that the melanocytes that make up moles are usually found on the bottom layer of the epidermis of the skin. With age, they may fall deeper into the skin and hence appear to vanish from the outside. However when some moles divide and grow they may spread up and down layers of the skin as well as grow abnormally. “The deeper down into the skin they go, the more likely it is that they have spread.” And once in the blood stream, as with any cancer, the major organs are at risk of infection.

Dr Wakelin explains how a cancerous mole is diagnosed, “It’s difficult to choose one sign. The most important question is whether it has changed recently? Any rapid change – darkening, becoming raised – is an indication, especially when it happens to just one mole but not to the others.”

It’s less of a worry when a person’s moles all change in the same way, she explains, because such general changes can be caused by events such as pregnancy.

As for spotting a cancerous mole, there is the “ABCD” basic guide. A is for asymmetry – is the mole the same on one side as it is on the other? The more symmetrical, the safer the mole. B is for border – does it have a smooth (fine) or ragged border (risky)? C is for colour. Is the mole a consistent colour throughout (good thing) or has it recently changed colour (bad thing). And D is for diameter. Any mole more than 6mm in diameter is suspicious.

I am a mole and I live in a hole

However, Dr Wakelin says these are only indicators, and not proof. If a doctor or dermatologist is concerned, the likelihood is that they will cut the mole out and have a look at it under a microscope.

Since they are quite small, the whole mole, plus a little extra outside it, is usually cut out down to the fat layer. This can mean an incision of as much as 1cm if it is on the back, or a very tiny slice if it’s on the eyelid. The hole is then stitched shut and left to heal, with usually with just a thin white scar remaining.

One patient, 29-year-old analyst Mark Fletcher* from London, had a mole removed from his face as a precautionary measure. “It took about 15 minutes after the anaesthetic was injected and I had about five stitches,” he says. The resulting scar is about 6mm long and 1mm wide. Fortunately, it is not that visible “except when in shadowy light”.

Lab tests on the mole revealed it was not cancerous. But there is a grey area, explains Dr Wakelin. “There are some moles that we call dysplastic, that are abnormal but not cancerous. If they are very dysplastic, it is best to have them removed. But it is difficult to tell.”

Beware of sunscreens

Fortunately, awareness of skin cancer in general means many cases are caught sooner. However, worryingly, the incidence of skin cancer in the UK continues to rise and, according to the latest figures, the death rate from skin cancer has now surpassed that of Australia.

Since sunlight is the most important environmental factor in the risk of melanoma, this may seem incredible in a country as sun-free as Britain. Ironically, it is the sunscreens designed to protect us that are thought to be aggravating the problem.

“Sunscreens help reduce UV exposure, but melanoma may not come from that,” Ms Wakelin explains. “It may simply be the amount of exposure to sunlight that causes more damage.”

Sunscreens also give people a false sense of security, she says. “If you don’t have burning to warn you, people may be over-exposing their skin.” People also tend to put too little on too infrequently – possibly due to the high-cost of such creams.

Instead, the official advice from doctors to help reduce the chances of skin cancer is to spend less time sunbathing, cover up the body with clothing and use strong sunscreens on the parts of the body that are exposed. Apart from that, keep a regular eye on your moles, and if you see any sudden changes in them, visit a doctor to be on the safe side.

Further information:

British Association of Dermatologists

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