Keep an eye on your moles. Go and see the doctor if they begin to itch, increase in size or change colour.

What is a mole?
A mole (or melanocytic naevus) is an abnormal collection of pigment cells present within the skin. These cells are known as melanocytes. Moles are extremely common. Most people are born with a few moles and develop others during their lives.

What causes moles?
Most moles are simply the result of a harmless proliferation of the pigment cells within the deeper layer of the skin. A few of these moles, called congenital melanonaevi, are usually present at birth. But most develop spontaneously or are caused by exposure to sunlight and tend to appear on those areas of the skin that catch the most sunlight. Most of these moles appear during the first 20 years of life, although they may continue to develop into the 30s and 40s. However, the majority disappear with age.

Why are moles a concern?
The main worry with moles is that a small number may go on to develop a condition called malignant melanoma. This form of skin cancer, which can be fatal, is best spotted early and treated with surgical excision (ie it is cut out of the skin).

Who is at risk?
The presence of moles will not cause you serious problems. But large numbers, more than 25, are an indication of susceptibility to melanoma. So you should take great care about exposure to sunlight. If there is a family history of malignant melanoma, you should be particularly vigilant about changing moles.

What are the symptoms of malignancy?

The mole is itchy and painful.

Increased size or an increasingly irregular appearance, especially at the edges.

A change in colour, particularly if the mole gets darker or becomes mottled.

Spontaneously bleeding.

Satellite pigmented lesions.

How is malignancy diagnosed?
Although most changes in the size, shape and colour of moles are due to a benign, non-cancerous increase in number of pigment cells, any mole that looks unusual should be examined. Your doctor will probably request information on recent changes to the mole along with a family history to assess your risk.

If only mild changes are found, your doctor will usually only need to take a clinical photograph of it. The mole's appearance may be reviewed in a later appointment. But if your doctor is concerned, an excision biopsy will be arranged, if necessary following a consultation with a plastic surgeon or a dermatologist.

Good advice
Avoid unnecessary exposure to sunlight, particularly during the two hours on either side of midday when the suns rays are strongest, and avoid getting sunburn.

Keep covered up in sunlight and apply sunscreen on exposed skin.

Examine your moles regularly and get someone to check those you cannot see.

Other types of moles include dysplastic, blue and halo naevi.

Dysplastic naevus syndrome Some large moles have an irregular outline and an indistinct border. These carry an increased risk of malignancy and tend to occur in families who have a history of malignant melanoma. Patients with such moles need to have them examined regularly and compared with clinical photographs.

Halo naevi
Occasionally the skin surrounding a small mole becomes lighter and the central mole becomes pale. Most halo naevi are benign. But some people may have an increased risk of developing the skin disorder, vitiligo. Patients with malignant melanoma may, very rarely, develop halo naevi.

Blue naevus
This deep-seated mole appears blue. It is very common in some West Indian infants but is only rarely of any significance.

Juvenile melanoma (Spitz naevus)
In this condition, the pigment cells form a benign tumour, which is usually a pink-brown colour. Although similar to melanoma, the outlook following treatment is good.

Common misconceptions
It is not true that moles on the soles of the feet or hairy moles are more likely to become malignant (cancerous).

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