The short answer
Most moles are harmless and rarely turn into melanoma. The changes worth checking follow the ABCDE guide: Asymmetry, Border irregularity, Color variation, Diameter usually larger than 6 mm, and Evolving (changing). A mole that changes, itches, or bleeds is worth showing a doctor.
Most moles are harmless and rarely turn into melanoma.
The ABCDE guide flags moles worth checking: Asymmetry, Border, Color, Diameter, Evolving.
A mole that changes, itches, or bleeds is worth a doctor's look.
A new mole, or a change in an existing one, is worth telling a doctor about.
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The simple version
Most adults have moles, and NCI says they rarely turn into melanoma. NCI says people should tell their doctor about a new mole or a change in an existing one. The ABCDE rule is a checklist for what to look for.
The ABCDE rule
- Asymmetry: one half of the mole does not match the other half.
- Border: the edges are ragged, notched, or blurry instead of smooth.
- Color: the mole has more than one color, or an uneven color, rather than one even shade.
- Diameter: melanoma (a serious skin cancer) is usually larger than 6 millimeters across, about the size of a pencil eraser, though it can be smaller.
- Evolving: the mole is changing in size, shape, or color over time.
Tell a doctor if you notice any of these features. NCI also lists changes in texture or hardness, and bleeding, oozing or itching, as reasons to get a mole checked.
What a doctor checks next
A dermatologist (skin doctor) examines the mole. If a mole raises concern, the doctor may do a skin biopsy, which removes tissue to test. NCI describes several types, including:
- A shave biopsy, which uses a small blade to remove the top of the growth.
- An excisional biopsy, which removes the entire growth with a scalpel.
The sample goes to a lab, where a pathologist (a doctor who studies tissue) checks it under a microscope. NCI says the pathologist typically sends the report to your doctor within 10 days after the biopsy or surgery.
Speak up about any mole you are worried about
Mention any mole that worries you, even if the doctor does not flag it first.
When to get help sooner
Nothing about a mole calls for an ambulance. Speed here means weeks, not minutes.
- Call your care team the same day if a mole is bleeding on its own, weeping, or has broken into a sore that will not close over.
- Call your care team within a day or two if a spot has visibly shifted in size, shape, or color over a few weeks, itches or stings without letting up, or is new.
What to ask your doctor
- Can you check this mole [describe location and changes]?
- Should I have a full-body skin exam?
- How often should I have my skin checked given my risk factors?
- Should this be biopsied, or can we watch it?
Sources
Common questions
Are most moles cancer?
No. NCI says most moles are harmless and rarely become melanoma. New or changing moles are worth checking.
What is the ABCDE guide?
It flags moles worth checking: Asymmetry, Border irregularity, Color variation, Diameter usually over 6 mm, and Evolving (any change over time).
What changes should I watch for?
A new mole, or one that changes color, size, shape or texture, itches, or bleeds or oozes, is worth a doctor's look.
How is skin checked?
A doctor or dermatologist can examine the skin and, if needed, take a sample (biopsy) of a suspicious mole.
Questions to ask your doctor
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Sources last checked: 2026-08-13 what this meansLast updated: 2026-08-18Next planned review: 2027-08-03
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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Editorial review complete — This page completed Cancer Explained's editorial checks (sources, safety, plain language, duplication). It has not been reviewed by a physician or other healthcare professional.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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