The mole guide: what does a cancerous mole look like?


Medically Reviewed April 2023, by Claire Clarke - Head of Surgical Services for The Harley Medical Group

Whether you are a sun worshipper or a casual tanner, it is important to check your moles for signs of skin cancer.

Skin cancer can develop if skin is exposed to harmful ultraviolet (UV) rays. These can damage skin cells and, in the worst cases, cause mutation. These mutated cells may proliferate as cancers, and are at risk of developing into malignant melanoma – the deadliest form of skin cancer.

If you are unsure whether a mole is normal, take a look at our visual guide below to see if you need a check-up. Consult your GP and dermatologist if you notice any of the warning signs on yourself.

Are all moles dangerous?

Most moles are harmless (benign), but some can develop into melanoma. Anybody who has more than 100 moles are at the greatest risk of melanoma, so it is a good idea to check your skin every few months for any noticeable changes.

Moles are most commonly found on areas that often catch the sun, such as the back, legs, arms and face. However, many cancerous moles hide in unsuspecting areas, such as the scalp, behind the knees, under the fingernails, between the toes and on the soles of the feet.

For men, malignant moles are most commonly found on the back, and for women they are often found on the lower leg. However, if protected well, moles in these areas are harmless.

Types of moles

There are many types of moles, but the most common have the following attributes:

  • Brown, round and flat - called ‘junctional melanocytic naevi’ moles.

junctional nevus

  • Raised, pale and hairy - called ‘dermal melanocytic naevi’ moles.

dermal nevus

  • Raised, light brown and hairy - called ‘compound melanocytic naevi’ moles.

dermal nevus

Rarer moles include:

  • Surrounded by a white ring – called ‘halo naevi’

halo nevus

  • Large, in a range of colours – called ‘dysplastic naevi’

dysplastic nevus

  • Dark blue – called ‘blue naevi’

blue nevus

Those who have a large number of moles - especially those with many dysplastic moles - should get them checked out. Other skin blemishes may be sun spots, freckles or a seborrheic keratose – these look similar to raised warts. All of these are harmless, but you should seek medical advice from a GP and dermatologist if you are concerned.

How to tell if a mole is cancerous

There are a few ways you can determine whether your moles need checking by a dermatologist. The first thing you should do is evaluate whether you are at risk of developing melanoma. Some of the most common factors include:

  • Over 100 moles on the body.
  • A family history of cancerous moles.
  • New moles developing.
  • Any changes in existing moles.
  • Fair skin.

Although more unusual, it’s not just people with fair complexions who can develop skin cancer. It is a good idea to watch out for any abnormal moles, regardless of your skin tone.

If one or more of these risks outlined above apply to you, you should seek guidance from your GP.

You can also check your moles at home using the ‘ABCDE’ strategy:


A – Asymmetry. If you draw a line through the middle, the two sides should match. If they don’t match, you should get this looked at by a medical professional.

B – Border. Benign moles have smooth, even borders. Moles with an uneven or ragged edge should be checked out.

C – Colour. Most benign moles are often a single shade of brown. Uneven colours on an individual mole, such as brown, tan, black, red, white or blue could be a sign of melanoma.

D – Diameter. Melanomas are usually larger in diameter than benign moles, and are usually at least 6mm in diameter.

E – Evolving. When a mole changes shape, size, colour or raises on the skin, you should consult your dermatologist. Remember to keep an eye on any new symptoms as well, such as bleeding, itching, crusting, or inflammation.

Check your moles every few months using the ‘ABCDE’ strategy for signs of new or changing moles. If at any time you notice one or more of these symptoms, you should make an appointment with your GP or consult a dermatologist as soon as possible.

What does a cancerous mole look like?

Cancerous moles (melanomas) tend to feature a mix of 2 colours or more and have ragged borders.


Unlike benign moles, most melanomas are larger, with a diameter of over 6mm

healthy mole vs cancerous mole

How to prevent cancerous moles

Along with checking your skin frequently for new or changing moles, you should also do as much as you can to prevent UV rays penetrating the skin.

Reduce your chances of developing skin cancer by doing the following:

  • Stay in the shade between 11am and 3pm, when the sun is at its strongest.
  • Cover up from harsh UV rays with a wide-brimmed hat, sunglasses and loose clothes.
  • Use a high SPF (minimum SPF15) and remember to reapply regularly, especially after swimming
  • Get regularly checked by a dermatologist who can help spot early symptoms

When to get a mole checked

If you are still worried about your moles, you should call your GP. If they are concerned, they will arrange a ‘mole check’ with a consultant dermatologist.

Justine Hextall, our consultant dermatologist at the Harley Medical Group, explains what she looks for when examining a mole:

“Firstly we take a careful history: how long has the mole been present? Is it new? Is it changing? Was the mole previously round and now has an irregular outline? Was the mole once a pale brown colour but is now darker or has variegate pigmentation with different shades of brown, black and even pink. Has the mole become raised? Does it just stand out and look different to the other moles the ‘ugly duckling’ sign? We may also ask whether the mole has begun to itch or bleed”.

A scanner or a dermatoscope will diagnose any atypical or abnormal moles. Any significant skin lesions will also be documented and photographed. If any seem suspicious and are showing signs of skin cancer, your dermatologist will refer you for mole removal.

Mole removal is usually done under local anaesthetic. A small injection numbs the area around the mole, and, once removed, it is sent to a laboratory to be checked under a microscope.

If it comes back that there are signs of cancerous cells, then more skin around the mole removal scar will have to be removed. Remaining stitches will usually be removed between seven and fourteen days, depending on the site of surgery. Your dermatologist will be able to advise on what to expect after mole removal.

Speak to your GP if you are concerned about your moles. For more information on moles and skin cancer, The Harley Medical Group are here to help. Book a free consultation today.


Posted July 18, 2020
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