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When should I have a mole checked out?

Woman has mole checked out.Melanoma – the most aggressive form of skin cancer – often develops as a new lesion but can sometimes develop from a pre-existing mole. It usually does not affect one’s life expectancy if it’s caught very early. That’s why it’s important to know the difference between normal moles and moles that might be dangerous.

Dr. Jensen Yeung, medical director at the Phototherapy Education and Research Centre (PERC) at Women’s College Hospital recommends that everyone does a self-check of their skin once a month to monitor for any suspicious moles.

“The common sites of melanoma are on the back, on the back of the legs, on the face, and, in dark-skinned individuals, on the palms and soles, and on the nails,” says Dr. Yeung. “But melanoma can occur anywhere on the body.”

That means you should check all skin areas, including hands, feet, scalp, and especially the back. If you don’t have anyone to look at your back for you, use two mirrors to get a good view of your own back.

When you’re examining moles, follow the ABCDE rules and look for any of the following suspicious signs:

A for asymmetry: if you draw a line down the centre of a mole, and the two halves do not match.

B for borders: borders of the mole are irregular or uneven instead of smooth and round.

C for colour: the mole is more than one colour or has uneven colouring.

D for diameter: if it’s more than six millimetres in diameter.

E for evolution: any change in size, shape or colour. This one – a changing mole – is the most important of the ABCDE characteristics.

Having any one of the danger signs doesn’t necessarily mean a mole is skin cancer, but do have a suspicious mole checked by a doctor.

In addition to the ABCDEs, Dr. Yeung also looks for what he calls “ugly duckling signs” – things that look out of the ordinary or out of place, that look different from the rest of the patient’s moles.

For people with lots of moles – more than 50 – it can be hard to keep track of whether a mole has changed or not. Dr. Yeung recommends having a set of photographs taken of their skin.

“Then they have something to compare it to, to see whether there are any new or changing moles.”

In addition to monthly skin checks, sun safety is important in preventing melanoma. Dr. Yeung recommends trying to stay out of the sun when the UV index is highest (between 10 a.m. and 4 p.m.), and using sunscreen regularly. Use a sunscreen with an SPF of 30 or higher with both UVA and UVB protection, apply it 15 minutes before sun exposure and reapply every two hours when outdoors.


This information is provided by Women's College Hospital and is not intended to replace the medical advice of your doctor or healthcare provider. Please consult your healthcare provider for advice about a specific medical condition. This document was last reviewed on: Mar. 25, 2019.

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