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5 Signs of a Cancerous Mole
June 18, 2025
Moles are a normal part of your skin – and most are nothing to worry about. But some can turn into melanoma, a serious type of skin cancer.
So how can you tell when it’s time to get a concerning mole checked?
We asked Jill Rubinstein, MD, PhD, a surgical oncologist with Hartford HealthCare’s Cancer Institute. She breaks down the top signs to watch for – and why early action matters.
1. It’s not symmetrical.
A healthy mole usually has a balanced shape – if you drew a line down the middle, both sides would look the same.
“If a mole is asymmetrical, where one half doesn’t match the other, it might be one sign that this is a mole to keep an eye on,” says Dr. Rubinstein.
“That uneven shape could signal abnormal cell growth and might push you to get it checked out,” she adds. “But remember, each individual sign is just one piece of information, and we’re looking for a pattern of changes.”
> Related: Your Summertime Guide to Preventing and Detecting Skin Cancer
2. The edges look uneven.
Typical moles tend to have smooth, clearly defined borders. But if the edges look jagged, blurred or scalloped, it could be a sign something’s not right.
“A cancerous mole will often have irregular or poorly defined borders,” says Dr. Rubinstein. “It’s a sign that the mole may be evolving in an atypical way. Be familiar with your skin and keep an eye on the shape and outline over time.”
3. The color isn’t consistent.
Most typical moles are all one color. But if you notice a mix of shades – like different tones of brown, black, or even hints of red, white or blue – it could be a warning sign.
“This variation in color can be an indicator of melanoma,” says Dr. Rubinstein. “It suggests that different types of cells may be growing in an uncontrolled way and might suggest that this one should be looked at.”
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4. It’s getting bigger.
Mole size isn’t everything – but it can be a clue.
“When a mole is larger than 6 millimeters – about the size of a pencil eraser – the chance of cancer does start to increase,” says Dr. Rubinstein. “But melanomas can be smaller, so size should always be considered alongside other changes like asymmetry or color variation.”
5. It’s changing over time.
A mole that starts to change – whether in size, shape, color or elevation – deserves a second look.
New symptoms like itching, bleeding or crusting can also be red flags.
“The evolution of a mole is one of the most important signs,” says Dr. Rubinstein. “If a mole is changing, it may be developing in ways that need medical attention.”
> Related: Where to Check for Skin Cancer, Based on Your Gender
See your doctor early.
If you notice a mole that looks different or starts to change, don’t ignore it.
A quick appointment with your doctor can give you peace of mind – or catch something early, when it’s most treatable.
“While the idea of skin cancer can be scary, early detection makes a huge difference,” says Dr. Rubinstein. “With regular skin checks – both at home and with your provider – you’re giving yourself the best chance for early treatment and great outcomes.”