Skin Cancer Explained

Cancerous moles – what do they look like?

Your guide to the signs of skin cancer in moles and how to tell if a mole is cancerous – with pictures.
MoleMap Team
August 2, 2021
12 minutes

Wor­ried about a mole that’s new, chang­ing or just looks unusu­al? Then you’re in the right place – this arti­cle out­lines the 9 com­mon signs of can­cer­ous moles, with help­ful pic­tures so you know the symp­toms to look for.

Most moles are harm­less but unfor­tu­nate­ly some aren’t – and it can be very dif­fi­cult to tell if a mole is can­cer­ous with an untrained eye. If you have a mole that’s show­ing some of the signs of skin can­cer below – or if you’re just not sure about it, book an expert full body mole check as soon as pos­si­ble — because the ear­li­er a can­cer­ous mole is detect­ed, the bet­ter the chances of suc­cess­ful treatment.

Read on to find out what warn­ing signs to look for and when you should get a sec­ond opinion…

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First­ly, what makes a mole cancerous?

Most moles or ​‘nevi’ are fair­ly harm­less. In gen­er­al, most Aus­tralian adults typ­i­cal­ly have some­where between 10 and 40 com­mon, or non-malig­­nant, moles on their body (note that if you have 50 or more moles, you may have a high­er risk of melanoma).1

Moles are essen­tial­ly clus­ters of melanocytes, the pig­ment-pro­duc­ing cells that increase the pro­duc­tion of melanin to pro­tect the skin against poten­tial­ly harm­ful UV

rays. Melanoma occurs when these melanocytes mutate and begin to divide uncontrollably.

The most com­mon cause of can­cer­ous moles is exces­sive expo­sure to UVA and UVB light (i.e. dam­age from the sun and sun beds), so the best thing you can do for your skin health is reduce your sun expo­sure, fol­low the Sun­Smart guide­lines – and have reg­u­lar, pro­fes­sion­al skin checks .2

What do nor­mal (non-can­cer­ous) moles look like?

A com­mon mole, also known as a ​‘nevus’, is a non-malig­­nant growth on the skin that often appears dur­ing child­hood or ado­les­cence. They are usu­al­ly pink, brown, or tan in colour and can take many dif­fer­ent forms, includ­ing freck­les, moles, skin tags, and seb­or­rhe­ic ker­atoses. Com­mon moles tend to look alike – they’re uni­form in shape and even coloured, rang­ing from 1mm to 10mm in size.

Almost all of us have moles, although they’re more preva­lent in those with lighter or freck­ly skin. Moles are not nor­mal­ly present at birth, but tend to appear in child­hood and ear­ly teenage years. Some moles may also light­en or dark­en with time as we age – espe­cial­ly with sun expo­sure. Gen­er­al­ly speak­ing, nor­mal moles are sta­ble — they’ll look the same a year from today.

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9 signs that a mole may be cancerous

When self-check­ing your skin (or the skin of a loved one), look out for any­thing NEW, CHANG­ING, or UNUSU­AL on both sun-exposed and sun-pro­tect­ed areas of the body.

Melanomas com­mon­ly appear on the trunks of men and the legs of women, but they can occur any­where — even in places that nev­er see the sun, like on the but­tocks, the soles of the feet, and the gen­i­tal area.4

Oth­er types of skin can­cer such as basal cell car­ci­no­ma and squa­mous cell car­ci­no­ma most com­mon­ly devel­op on parts of the body that receive high or inter­mit­tent sun expo­sure, such as on the face, scalp, neck, arms, shoul­ders and back.5

Look out for these 9 com­mon signs of skin can­cer when you check your skin:

  1. You notice a new mole — most moles appear appear dur­ing child­hood and ado­les­cence, so any new moles that appear if you’re aged over 25 (and espe­cial­ly if you’re aged over 50) could poten­tial­ly be can­cer­ous and should be checked out, espe­cial­ly if you notice the mole chang­ing – see below.6

  2. You have a mole that’s increas­ing in size –moles can grow slow­ly as you get old­er, but any rapid or sud­den change is some­thing to be con­cerned about and may indi­cate the pres­ence of fast-grow­ing melanoma. Moles that are larg­er than 6 mm in size (the diam­e­ter of a pen­cil eras­er) should be checked reg­u­lar­ly. Can­cer­ous moles can be small­er, but they don’t usu­al­ly stay that way and will grow over time.
  3. You have a mole that’s asym­met­ri­calin shape - most nor­mal, non-can­cer­ous moles tend to appear as a per­fect cir­cle — where­as most prob­lem moles are asym­met­ri­cal or lop-­sided. Asym­me­try in moles is one of the ​‘red flags’ for skin can­cer, so ensure you have any unusu­al­ly-shaped moles checked by your GP or skin can­cer detec­tion service.
  4. The edge of a mole has become notched or ragged – most nor­mal or com­mon moles tend to have sharp, well-defined bor­ ders. If your mole looks notched or ragged, or seems to spread or grad­u­al­ly blur into the sur­round­ing skin, it would pay to get it skin check. The bor­ders of an atyp­i­cal (can­cer­ous) mole are often irreg­u­lar and/​or ​‘hazy’ — symp­toms that become more pro­nounced as time goes on.
  5. You have a mole that’s dark­en­ing or chang­ing in colour – Most nor­mal moles are tan, brown, or the same colour as your flesh and are also uni­form in appear­ance. One part of the mole isn’t nec­es­sar­i­ly lighter or dark­er than any oth­er. If a mole appears to be mul­ticoloured — in that it has areas that are dark brown, blue, black or white, and even red — you should get a sec­ond opin­ion from MoleMap­ or your GP. This can be a sign of super­fi­cial spread­ing melanoma, the most com­mon form of melanoma.
  6. A mole is becom­ing raised or devel­ops a lump with­in it – this can be a symp­tom of nodu­lar melanoma, a par­tic­u­lar­ly fast-grow­ing and dan­ger­ous form of melanoma. The key give­away is that it’s raised, often sym­met­ri­cal, firm to touch, and is chang­ing or grow­ing pro­gres­sive­ly. Any raised, firm or grow­ing spots should be pro­fes­sion­al­ly checked as a precaution.
  7. The sur­face of a mole is becom­ing rough, scaly or ulcer­at­ed – small, rough or scaly patch­es on your skin can be actinic ker­ato­sis (solar ker­ato­sis) which is gen­er­al­ly caused by too much sun, and com­mon­ly occurs on the head, neck, or hands, but can be found else­where. They can become can­cer­ous over time, so it pays to get these checked reg­u­lar­ly for changes. How­ev­er, if a mole is ulcer­at­ed, you should get it checked imme­di­ate­ly – it is high­ly like­ly to be a melanoma and has a high­er risk of spread­ing than oth­er melanomas.7

  8. You have a mole that’s itchy, tin­gling, weep­ing or bleed­ing - Most can­cer­ous moles don’t hurt, but there are warn­ing signs, includ­ing itch­i­ness, tin­gling, bleed­ing or weep­ing. Just like the rest of the skin on your body, a mole can become itchy, or get injured and bleed as a result of injury – that’s usu­al­ly noth­ing to wor­ry about. How­ev­er, moles that bleed or ooze flu­id with­out being injured may be cause for con­cern – you should get these checked by experts just as soon as you can.

  9. You have a mole or spot that look dif­fer­ent from the oth­ers – the ​‘ugly duck­ling’. Most nor­mal moles on your body will look sim­i­lar in appear­ance, while melanomas often stand out like ugly duck­lings in com­par­i­son. These can be larg­er, small­er, lighter or dark­er when com­pared to sur­round­ing moles – or they may be iso­lat­ed with­out any sur­round­ing moles. That’s why it’s impor­tant to not only check your moles, but also to com­pare them – this is a vital part of any pro­fes­sion­al full body mole check and mon­i­tor­ing ser­vice such as a Full Body MoleMap.

Oth­er help­ful guides devel­oped by der­ma­tol­o­gists for detect­ing skin can­cer are the ABCDE and EFG rules – you can check them out here. You can also find our help­ful guide for self-check­ing your skin. And read on for the answers to oth­er fre­quent­ly asked ques­tions about can­cer­ous moles…

Can a nor­mal mole become cancerous?

The short answer is yes. For adults, new moles and sud­den changes to exist­ing moles can be a sign of melanoma. Accord­ing to Yale School of Med­i­cine, approx­i­mate­ly 70 per­cent of melanomas appear on nor­mal skin, while 30 per­cent orig­i­nate in a pre­-ex­ist­ing mole in which changes in col­or, size, and/​or shape have occurred.8

Can I detect a can­cer­ous mole myself?

We thor­ough­ly rec­om­mend reg­u­lar self-checks so you can get to know your skin and moles. But please bear in mind that no mat­ter how vig­i­lant you are about check­ing your skin, many of the signs of skin can­cer are very dif­fi­cult to see with an untrained eye — espe­cial­ly in the ear­ly stages.

Note also that a sin­gle exam­i­na­tion of your skin isn’t enough to assume a mole will remain nor­mal. One of the major indi­ca­tions of can­cer­ous moles is that they con­tin­ue to grow and change shape and colour, and these symp­toms gen­er­al­ly become more pro­nounced over time – which is why we rec­om­mend a mole check to track changes in your skin and moles over time.

Can a doc­tor tell if a mole is can­cer­ous just by look­ing at it?

If the skin can­cer is start­ing to advance, then yes, the symp­toms may be obvi­ous to the naked eye. How­ev­er, the ear­ly signs of melanoma skin can­cer aren’t always vis­i­ble at a glance.

That’s why a group of der­ma­tol­o­gists pio­neered the Full Body MoleMap, which involves tak­ing high-res­o­lu­tion, close-up images of any at-risk moles and spots, and com­par­ing them at sub­se­quent appoint­ments. This method­ol­o­gy can improve the chances of detect­ing any poten­tial skin can­cers much ear­li­er than visu­al checks – because the ear­li­er skin can­cer is found, the bet­ter the chances of beat­ing it.9

What are the risk fac­tors for get­ting can­cer­ous moles?

The most com­mon risk fac­tors for melanoma skin can­cer are:

  • fair and/​or freck­ly skin that burns easily
  • fair, blonde or red hair
  • hav­ing been sun­burnt in the past or used sunbeds
  • hav­ing a lot of moles (50+)
  • being over 50 years old
  • lead­ing an out­door lifestyle or hav­ing high dos­es of inter­mit­tent sun (e.g. on holiday)
  • a per­son­al or fam­i­ly his­to­ry of skin can­cer, espe­cial­ly melanoma
  • Cer­tain med­ica­tions, includ­ing immune-sup­pres­sion med­ica­tions.10

If you’re not sure of your risk lev­el, take this quick skin can­cer risk quiz. And if you think you may be at high­er risk, we high­ly rec­om­mend a com­pre­hen­sive skin check every year.

How often should I get my skin checked for can­cer­ous moles?

The lat­est sta­tis­tics from the US show that patients whose melanoma is detect­ed ear­ly have a 99% five-year sur­vival rate. This drops to 66% if melanoma reach­es the lymph nodes, and 27% if it spreads to dis­tant organs.11 All good rea­sons to have a skin cancer check every year.

At Australia skin cancer clinic like MoleMap, we recommend

  1. A self-check every 3 months (or every month if you’re high risk) – you can down­load our help­ful self-check guide here.
  2. A GP check every 6 months — in between your reg­u­lar mole-map­ping appointments.
  3. A Full Body MoleMap or Skin Check every year – see which ser­vice is right you here.

Remem­ber, if you’re wor­ried about a mole, don’t chance it: check it. It may just save your skin – and your life.

1. 2. Melanoma Institute Australia: 3. 4. Melanoma Institute Australia: 5. Cancer Council of Australia: 6. Melanoma Institute Australia: 7. Melanoma Institute Australia: 8. 9. Melanoma Institute Australia: 10. Melanoma NZ: 11.

MoleMap Team

At MoleMap we check, detect and treat skin cancer. Find out how you can protect your skin at your nearest MoleMap skin cancer clinic.

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