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Written by Prof James Ferguson, consultant dermatologist
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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.
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| Keep an eye on your moles. Go and see the doctor if they begin
to itch, increase in size or change colour. |
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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?
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The mole is itchy and painful.
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Increased size or an increasingly irregular appearance,
especially at the edges.
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A change in colour, particularly if the mole gets darker or
becomes mottled.
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Spontaneously bleeding.
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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 sun’s 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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Last updated 02.06.2005
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