Is This Mole Cancerous? A Self-Exam Guide

Almost everyone has moles, and the overwhelming majority are completely harmless. But learning to recognize the difference between an ordinary mole and one that needs a professional look is one of the most useful skills you can have — because when it comes to melanoma, catching it early is the single biggest factor in outcome.

The ABCDE Rule, Explained in Full

Dermatology Professionals use five features to evaluate whether a mole looks suspicious. No single feature on its own is a diagnosis, but if a mole has one or more of these, it's worth getting checked.

• A — Asymmetry. Draw an imaginary line through the middle of the mole. In a normal mole, the two halves roughly match. In a concerning one, they don't — one half looks noticeably different from the other.
• B — Border. Benign moles tend to have smooth, even borders. Watch for edges that are ragged, notched, blurred, or poorly defined.
• C — Color. A single, uniform shade of brown is typical of a normal mole. Multiple colors within one mole — shades of brown, black, red, white, or blue — are a warning sign.
• D — Diameter. Melanomas are often (though not always) larger than 6mm across — roughly the size of a pencil eraser — at the time they're diagnosed. Smaller spots can still be concerning if they have other features.
• E — Evolving. This is arguably the most important letter. Any mole that is changing — in size, shape, color, elevation, or symptoms like itching or bleeding — deserves an evaluation, regardless of how it scores on the other four criteria.

Beyond ABCDE: The "Ugly Duckling" Sign

Dermatology Professionals also look for what's called the "ugly duckling" sign — a mole that simply looks different from all your other moles. Most people have a fairly consistent pattern to their moles; one that clearly stands out from the rest, even if it doesn't obviously break the ABCDE rules, is worth a second look.

How to Do a Skin Self-Exam at Home

A thorough self-exam takes about 10 minutes and is worth doing monthly:

1. Use good lighting and a full-length mirror, plus a hand mirror for hard-to-see areas. 2. Work head to toe systematically — scalp (parting hair with a comb), face, ears, neck, chest, and torso. 3. Check your arms, including the undersides, palms, and between fingers. 4. Don't skip your back — it's the most common site for melanoma in men and hard to self-examine. Use a hand mirror, or better, ask a partner to check it for you. 5. Check your legs, including the backs, using the hand mirror or sitting down to get a clear view. 6. Don't forget your feet — soles, between toes, and toenails. Melanoma on the feet is often diagnosed late simply because people don't look there. 7. Check your scalp and any areas covered by hair or clothing, which get missed most often.

Take photos of any moles you want to track over time — it makes it much easier to notice genuine change at your next self-exam, rather than relying on memory.

What to Do If You Find Something Concerning

If a mole meets one or more ABCDE criteria, stands out as an "ugly duckling," or has changed noticeably, don't wait to see if it gets worse. Schedule a professional skin exam. Most suspicious moles turn out to be benign, but the only way to know for sure is a dermatology professional's evaluation — and if a biopsy is needed, it can typically be done in the same visit.

How Often Should You Self-Exam and Get a Professional Skin Check?

Dermatology Professionals generally recommend a monthly self-exam and an annual professional full-body skin exam for most adults — more frequently if you have risk factors like a personal or family history of skin cancer, many moles, fair skin, or significant sun exposure history.

Sources: American Academy of Dermatology; Skin Cancer Foundation.