Flat or raised growths on the skin that are rough or smooth and vary in colour from light to dark brown

  • Increasingly common in childhood and adolescence
  • Sometimes run in families
  • Gender and lifestyle are not significant factors

Moles are caused by an overproduction of pigmented skin cells called melanocytes. They can form anywhere on the body, and there are several types. Moles may appear soon after birth (see Birthmarks) or may appear during childhood and early adolescence; nearly all adults have 10–20 moles by the age of 30. Most moles are noncancerous, but in rare cases a mole may undergo changes that make it cancerous (see Malignant melanoma). Alterations in the shape, colour, or size of moles are not always a sign of cancer, and changes during puberty or pregnancy are usually normal. However, changes should always be evaluated by a doctor.

What are the types?

Usually, moles are flat or raised growths that vary in colour from light to dark brown and measure less than 1 cm ( 3 / 8 in) in diameter. They may be rough or smooth, hairy or hairless.

One type of mole, known as a dysplastic naevus, is larger than usual and unevenly coloured. This type may appear in childhood or old age, and may develop from a smaller mole. Dysplastic naevi sometimes run in families, and are more likely to become cancerous than other moles. The risk is higher in people who have a family history of malignant melanoma or if the mole is frequently exposed to sunlight.

Blue naevi are noncancerous moles that have a bluish-black colour and occur most commonly on the face, arms, legs, and buttocks.

A halo naevus is a mole from which pigment is disappearing, leaving a ring of paler skin around a shrinking central dark spot. Eventually, the mole may disappear completely.

What might be done?

You should check your skin regularly and consult your doctor if you notice any changes that might be a cause for concern (see Checking your skin)

If your doctor suspects that a mole is cancerous, he or she may recommend that you have it removed and examined for cancerous cells (see Skin biopsy). Noncancerous moles can also be removed, either for cosmetic reasons or if they are being chafed by clothing. However, removal of a mole does not always produce cosmetic improvement.

Raised mole

This noncancerous mole appears as a raised, brown spot; the area of pigmentation may extend deep into the skin.

Hairy mole

Moles that are covered in hair, such as the one shown here, or moles with just a few hairs rarely become cancerous.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

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