Is a Changing Mole a Sign of Cancer?

This page is for anyone with a mole or skin spot that seems to be changing. It explains what to look for, where to check, and how quickly to get it seen.

Most guidance about moles gets remembered as a size rule. That is not quite what the NHS (the UK's National Health Service) says.

Its line is that normal moles usually do not change over time. A mole that changes size, shape or color may be a melanoma, the most serious type of skin cancer. So the question to ask about a spot is not "is it big?" but "is it doing something?"

That is also why this is one symptom where waiting to see is the wrong instinct. Waiting produces more change, which is the finding you already have.

The NHS sets the two side by side, which is more useful than a checklist.

• Shape. Normal moles are usually round with smooth edges. Melanomas are often an uneven shape, sometimes with two differently shaped halves and ragged edges.
• Color. Normal moles are usually one color. Melanomas often mix two or more.
• Size. Normal moles are often about the width of the end of a pencil or smaller. Melanomas tend to be bigger, often more than 6mm across, though they can be smaller when found early.
• Behaviour. Normal moles usually stay the same. A mole that changes size, shape or color may be melanoma.

Beyond shape and color, the NHS lists other signs to look for: moles that are swollen and sore, bleeding, itchy, or crusty.

The American Cancer Society lists warning signs for the commoner skin cancers too: a new spot or bump that is growing or changing in shape or color, a sore that bleeds and does not heal after several weeks, and a rough or scaly red patch that might crust or bleed. It says to see a health care provider about any new or changing growth or a sore that does not heal.

Melanoma tends to appear on skin that gets a lot of sun. But the NHS notes that rarer types can affect the eyes, the soles of the feet, the palms of the hands and the genitals.

That matters because those are the places nobody checks. A new dark spot on a sole or palm, or a new dark line down a nail, is worth showing a doctor for the same reason as any changing mole.

Use a mirror for your back, or ask someone to look.

A doctor sees your mole once. A photo lets them see it twice.

Put a ruler, a coin or a fingernail beside the spot for scale. Use daylight if you can, and hold the camera steady at about a hand's distance. Save the date. Take the next one from the same angle a few weeks later.

If you have older holiday photos that happen to show the same patch of skin, bring those too.

The NHS says a doctor may ask about your health, your symptoms and how much time you spend in the sun, and will look at the affected skin. They may ask to take a photograph to send to a dermatologist (a skin doctor).

You may then be referred for more tests. The NHS is careful to add that a referral does not mean you have cancer. Our page on preparing for appointments covers what else is worth bringing.

• Call your primary care doctor or care team the same day if a mole or spot is bleeding and will not settle, or has become swollen, sore and weepy.
• Call your primary care doctor or care team within a day or two to book an appointment if a mole has changed its size, its shape or its color, if it has taken on uneven edges or two or more colors, or if a sore or patch of skin has bled, crusted or scabbed and not healed after several weeks. The same applies to a new dark spot on a palm or sole, and to a new dark line running down a nail.

• NHS — Symptoms of melanoma skin cancer
• NHS — Symptoms of non-melanoma skin cancer
• National Cancer Institute — Symptoms of Cancer
• American Cancer Society — Signs and Symptoms of Melanoma Skin Cancer
• American Cancer Society — Signs and Symptoms of Basal and Squamous Cell Skin Cancers