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How Do I Know If a Mole Is Cancerous?

How Do I Know If a Mole Is Cancerous?

Most moles are not serious, but if they change in size, shape or colour, they should be assessed by a physician.

What is melanoma?

Melanoma is a malignant tumour of the skin that can resemble a mole. It can occur at any age and, if detected early, it can be completely cured. However, lifetime monitoring of your skin will then be necessary to watch for recurrence.

What are the signs of melanoma?

  • Melanoma may develop as a small spot on previously normal skin, or it may develop from a pre-existing mole. The spot enlarges, changes in shape and colour, and may thicken.
  • There is no blood test to detect melanoma, the diagnosis is made by physical examination and skin biopsy.

How can I identify a suspicious mole?

  • It changes appearance.                                                        
  • New spots appear around the original spot (satellite lesions).
  • A crust forms, disappears and reforms on the surface of the spot.
  • It bleeds easily with little injury and heals poorly.

Are some parts of the body more prone to melanoma?

  • Moles at a risk for cancer can be located anywhere on your body, even on the genital organs or under the finger or toenails.
  • There are nonetheless some more common areas to watch: the calf in women, the back in men, and the cheeks in elderly people.

When should I see the doctor? : the A, B, C, D, E test

A = Asymmetry. The mole has an odd, irregular, asymmetrical form.
B = Border. The edge of the mole has the look of a geographic map.
C = Colour. The mole shows several tints: pinkish brown, reddish brown, blackish beige.
D = Dimension. The mole is more than 8 mm in diameter.
E = Evolution. The mole's size has increased or you feel new sensations (example: itching).

If you answer “yes” to one of these criteria, your mole should be examined by a physician.


Does the sun play a role in causing melanoma?

  • Repeated high level exposure to the sun – especially exposure that resulted in sunburns during childhood and adolescence — is the most dangerous and doubles the risk of developing a melanoma.
  • Two out of three melanomas are linked to excessive sun exposure.
  • Regular exposure to artificial UV light (for example, using tanning lamps or the solarium in tanning centres) doubles the risk of melanoma.

Are some people at greater risk?

Some people are at greater risk for developing melanoma:

  • Those with fair skin and hair who sunburn easily
  • Those who work outdoors and have a lot of sun exposure
  • Those who use UV lamps without skin protection
  • Those who have many moles greater than 5mm in size (please note: not all moles degenerate into cancers, in fact fewer than 10% of the melanomas develop from a pre-existing mole).
  • Those with a family history of melanoma. In about 10% of the cases the cause is genetic.

Monitor your moles regularly. If you find changes in the shape, colour, size, border or sensation, you should consult your doctor.

Publication date:   5/12/10

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TLC-DOC is a service provided by local GPs, with the support of the HSE, and located in Tallaght Cross west across from Aldi Tallaght Rd, Cookstown, Dublin. Local GPs have formed a cooperative to provide out-of-hours care for their own patients. This service will provide GP appointments for urgent medical conditions on weekday evenings and weekends. 1890 20 22 24 Please do not ring this number before 6.00 pm Monday - Friday, or 10.00 Sat/Sun & Bank Holidays.

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