How to Tell if a Mole is Cancerous
Finding a mole that looks different from the others is unsettling. Most people notice a change and spend days wondering whether it matters. The honest answer: some moles need attention quickly, and some do not. The tricky part is knowing which is which without medical training.
This article walks you through the specific signs that separate a mole worth monitoring from one that needs a doctor’s assessment, so you can make a clear, informed decision about what to do next.
The ABCDE Rule: What to Look for in a Suspicious Mole
The most widely used framework for assessing moles comes from dermatology and is known as the ABCDE rule. Each letter points to a specific feature that can indicate a mole has changed, or is growing in a way that warrants medical assessment.
A is for Asymmetry
Asymmetry means the two halves of the mole do not match. If you drew a line through the middle and one side looked noticeably different from the other, that is asymmetry. Most benign moles are symmetrical. An irregular shape does not confirm cancer, but it is a clear prompt to have the mole assessed.
B is for Border
Border refers to the edges of the mole. A healthy mole typically has a smooth, well-defined border. A mole with irregular, ragged, notched, or blurred edges sits outside what is considered normal and should be reviewed by a doctor.
C is for Colour
Colour variation within a single mole is one of the more reliable early indicators of concern. A normal mole is usually one uniform shade of brown or tan. Multiple colours in one mole, including different shades of brown, black, red, pink, white, or blue, are a sign that something may be happening at the cellular level.
D is for Diameter
Diameter above 6mm, roughly the size of a pencil eraser, is the threshold most guidelines flag. That said, melanomas can be smaller than 6mm, particularly in the early stages. Size alone is not the deciding factor; it is one of several things to weigh together.
E is for Evolution
Evolution is the most important letter. A mole that is changing in any way, whether growing, shifting colour, changing shape, starting to bleed, itch, crust, or become raised, needs medical attention. Even if every other feature looks normal, a mole that has changed is a mole that should be checked.
Other Changes That Should Prompt a Skin Check
Beyond the ABCDE framework, several other signs are worth paying attention to. Book a skin check if you notice any of the following:
- A new mole that appears after the age of 40
- A spot that bleeds without being scratched or bumped
- A mole that has become itchy, tender, or painful
- Any lesion that looks noticeably different from all other moles on your body (sometimes called the “ugly duckling” sign)
- A spot or sore that has not healed after three to four weeks
These signs do not mean a mole is definitely cancerous. They do mean a clinical assessment is the right next step.
What Does a Normal Mole Look Like?
Not every unusual-looking mole is cause for alarm. A normal mole is generally:
- Round or oval with a smooth, even border
- A single, uniform shade of tan, brown, or (less commonly) pink
- Flat or only slightly raised above the skin surface
- Smaller than 6mm across
- Stable, meaning it has not changed in recent months or years
Many people have moles that sit slightly outside one of these criteria without that being a sign of anything concerning. What matters most is whether a mole has recently changed, or whether it stands out clearly from all other moles on your body.
Who Is at Higher Risk of Melanoma in Australia?
Australia has one of the highest melanoma rates in the world. The Cancer Council Australia reports more than 15,000 new melanoma diagnoses annually, making it the third most common cancer in the country. Roughly 2 in 3 Australians will be diagnosed with some form of skin cancer before the age of 70.
Certain factors increase personal risk:
- Fair skin, red or blonde hair, or blue or green eyes
- A history of sunburn, particularly blistering sunburn during childhood
- A large number of moles (more than 50 on the body)
- A personal or family history of melanoma or other skin cancers
- Significant cumulative sun exposure over many years
- Use of solariums or UV tanning equipment
Higher risk does not mean a concerning mole is definitely cancerous. It does mean being more vigilant and having skin checks as a regular part of preventive care rather than only when something appears wrong.
When to See a Doctor About a Mole
If a mole matches any of the ABCDE criteria above, or if it has changed recently in any way, the right step is to have it assessed by a doctor. You do not need to reach a diagnosis yourself. That is exactly what the consultation is for.
At Knox GP, GPs with a special interest in skin cancer medicine perform comprehensive, full-body skin cancer checks. Dr Paul Sabeti, Dr Monirul Khan, and Dr Majid Mehdipour all offer dedicated skin checks, bringing years of experience in skin cancer detection and management.
The initial skin check is bulk-billed for all patients with a valid Medicare card, meaning no out-of-pocket cost, regardless of concession status. The appointment takes around 15 to 30 minutes. If a mole needs further assessment, your doctor will explain the next steps and any associated costs clearly before anything is done.
No referral is needed. Book a bulk-billed skin cancer check at Knox GP online or call the clinic on 03 9100 3130.
NOTE This article provides general health information only and does not constitute medical advice. Statistics sourced from the Cancer Council Australia (cancer.org.au) and the Australian Institute of Health and Welfare (aihw.gov.au). For information on recognising specific mole changes, see also: Healthdirect Australia (healthdirect.gov.au).
