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Skin Cancer Explained

The signs of skin cancer you need to know

The idea of skin cancer can be scary. Yet, knowing the signs can help you to spot it early—when it’s most treatable.
January 19, 2024
5 minutes

Skin cancer accounts for 80% of all newly diagnosed cancer. The good news is that you can reduce the risk. The first step is adequate sun protection, of course. The second step is to know the 7 signs of skin cancer. A great way to do this is by learning the ABCDEFG rule. Let’s look at how to use it.

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What is the ABCDEFG rule

This clever guideline for detecting skin cancer signs was first introduced in 1985. Back then it was simply the ‘ABCD’ rule. In 2004 it expanded and became the ‘ABCDE’ rule to encompass more signs of skin cancer. 

At some point over the last 20 years, further signs of skin cancer have been added. We now have seven signs of skin cancer to watch for. The acronym stands for:

Asym­me­try

Bor­der

Colour

Diam­e­ter

Evolv­ing or ele­vat­ed

Firm

Grow­ing

Infographic of the ABCDEFG rules to spot skin cancer.
The seven signs used to spot early signs of skin cancer and the ‘ugly duckling’ mole.

Spotting signs of skin cancer (ABCDEFG rule)

Let’s take a closer look at how the ABCDEFG rule is used to spot the early signs of skin cancer.

A — stands for asymmetry

Most non-cancerous moles are symmetrical. Cancerous lesions on the other hand tend to be asymmetrical. If you spot a suspicious mole, take a close look to see if one side matches the other.

B — stands for border

Cancerous moles often have irregular borders. The edges may be blurred or jagged. Also, the pigment may spread into the surrounding skin.

Images of cancerous moles with blurred edges.
Cancerous moles often have irregular borders, the edges may be blurred and are no longer well defined.

C — stands for colour

You’ll notice that most of the moles on our body are quite even in colour. Usually, brown. Cancerous lesions can vary in colour. There may be shades of brown, tan and black. There may also be areas of pink, red, white, or blue.

D — stands for diameter

Worried about a suspect mole? Ask yourself if it has changed in size. Cancerous moles can increase in size. Certainly, if the mole is larger than 6 millimetres this may be a warning sign of skin cancer.

E — stands for evolving/elevated

Non-cancerous moles don’t tend to change in shape, size, or colour. If you notice a spot has evolved over time, has become elevated, thickened or even itchy, get yourself checked.

Images of evolving moles which can be an early sign of skin cancer.
If you notice a spot has evolved over time, has become elevated, thickened or even itchy, get yourself checked as non-cancerous moles don’t usually change over time.

F — stands for firm

While benign lesions can feel firm, it’s also a feature of nodular melanoma. This is an invasive form of skin cancer. It’s less often associated with sun exposure, compared to other types of melanoma. Nodular melanoma accounts for about 15% of melanoma in Australia and New Zealand. It commonly appears as a large mole (bigger than 6mm) and is often dome-shaped.

G — stands for growing

Nodular melanoma can grow quickly—over days or weeks. If you notice any spot or mole getting larger, have it looked at ASAP.

It’s important to know that the physical signs of skin cancer can vary from one person to the next. First signs of skin cancer may also depend on the type of skin cancer. For more information, check out this article outlining the other symptoms of skin cancer.

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Other skin cancer signs

  • Additional early warning signs of skin cancer to watch for include: 
  • A new spot or mole
  • A sore that doesn’t heal
  • The ‘ugly duckling’ — a mark that looks different from all the others
  • A spot or mole that changes in sensation — becomes itchy, painful, or tender
  • A spot that weeps or bleeds
  • Vision problems - blurriness, dark spots, loss of peripheral vision

Pictures of ugly duckling moles.
An ‘ugly duckling’ mole is a mark that looks different from all the others and should be checked straight away.

Checking your skin for skin cancer signs

Now that you know the beginning signs of skin cancer, get into the habit of checking your skin. We recommend booking an annual skin exam at a MoleMap skin cancer clinic and self-examining your skin every 3 months. 

To perform a thorough DIY skin examination, you’ll need:

  • A chair
  • Full-length mirror
  • Hand-held mirror
  • Good lighting
  • A friend or partner for those tricky-to-see spots
Young lady examines her skin in the bathroom mirror.
We recommend booking an annual skin exam at a MoleMap skin cancer clinic and get into the habit of self-examining your skin every 3 months.

As you examine your skin, keep the ABCDEFG rule in mind. Even better, print it off to refer to. Your skin self-exam should leave no spot unchecked. Common areas to miss are the palms, soles of the feet, between fingers and toes and under nails. To get the most from your DIY skin exam, take a look at this comprehensive guide to checking your skin.

What’s your risk of skin cancer?

Skin cancer doesn’t discriminate; it can affect anyone. Sun exposure is one of the biggest risks. Yet, several factors increase your risk of skin cancer. This includes:

  • A family/person history of skin cancer
  • Pale or freckled skin
  • Skin that burns easily
  • A history of sunburn or solarium use
  • An outdoors job/lifestyle
  • A high number of moles or irregular lesions

While skin cancer can strike at any age, the risk increases as you age. Most skin cancers typically appear after the age of fifty. Learn about your personal skin cancer risk.

The key to early detection is to be vigilant. If you notice any new or unusual spots, find a skin clinic near you to get it quickly checked out. If you know your risk is moderate to high, we recommend a Full Body MoleMap. This is our most comprehensive mole check. It includes total body photography and ongoing monitoring to spot changes to your moles over time.

Young woman in the sun wearing a wide brim sun hat.
The key to early detection is to be vigilant. If you notice any new or unusual spots, find a skin clinic near you to get it quickly checked out.

If you’re low risk or have spotted a new or changing mole, we suggest our skin check service. This includes a thorough skin examination with any suspicious moles sent for dermatologist diagnosis. For extra peace of mind you may choose our SkinCheck+. This provides the added benefit of total body photography, so you can track changes to your skin in between your annual skin screenings.

Ultimately, a regular skin examination helps to spot skin cancer early. This can be the difference between a simple excision and more aggressive treatment.

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