Melanoma: the ABCDE rule and how to check your moles

In short

• A new mole, or a change in an existing mole, may be a sign of melanoma. Change over time is the most important warning.
• The ABCDE rule describes what to look for: asymmetry, border, color, diameter and evolving.
• Melanoma can occur anywhere on the skin, including the soles of the feet, the palms and under a nail.
• People with dark skin can get melanoma too, so a changing spot should be checked on any skin tone.
• Do not cut out or burn off a mole at home. Only a biopsy, where the cells are examined under a microscope, can show what a spot is.

What melanoma is and why early detection matters

Melanoma starts in melanocytes, the skin cells that make pigment. The CDC describes it as causing more deaths than other types of skin cancer because it can spread to other organs, such as the brain and liver.

The good news is that skin is the one place where you can see changes yourself. The NHS notes that finding melanoma as early as possible can make it easier to treat.

The ABCDE rule

1. A: Asymmetry.One half of the spot does not match the other half.
2. B: Border.The edges are ragged, notched or blurred instead of smooth.
3. C: Color.The color is not the same throughout, with more than one shade within the same spot.
4. D: Diameter.The spot is usually larger than 6 millimeters across. Smaller spots can still be melanoma, so size alone does not clear a mole.
5. E: Evolving.The spot changes over time in size, shape, color or in how it feels.

Another check is the ugly duckling sign: if one spot looks clearly different from the rest of your moles, have it looked at even if it does not tick every ABCDE box. The NHS also lists itching, bleeding, crusting, swelling or soreness in a changing mole as reasons to be seen.

How to check your skin

1. Set up.Use bright light, a full-length mirror and a hand mirror. Ask someone you trust to look at your back and scalp.
2. Front and sides.Check your face, ears, neck, chest, belly and underarms, and the sides of your body.
3. Arms and legs.Check your hands, including the palms and between the fingers, then your legs, feet, soles and between the toes.
4. Under the nails.Look for a dark streak under a nail that was not caused by an injury. The NHS lists it as a sign to get checked.
5. Keep a record.Note any spots that worry you. If you take photos, use the same lighting each time so you can compare.

Who has a higher risk

• A history of sunburns, especially many blistering sunburns in childhood or the teen years.
• Using tanning beds or other artificial sunlight.
• A lighter natural skin color, or skin that burns, freckles and reddens easily.
• Several large moles, many small moles, or atypical moles, and a family history of atypical moles or skin cancer.
• A weakened immune system.

Anyone can have melanoma, including people with dark skin. It can also appear on parts of the body that get little sun, such as the soles of the feet, the palms and the genitals. So a lack of tanning is not a guarantee.

When to see a doctor, and red flags

See your primary care provider or a dermatologist if a mole has changed in shape, size or color, is itchy or painful, or is bleeding, crusty or inflamed. Also get checked for a new or unusual mark that has not gone away after a few weeks, including on the palms or soles, and for a dark area under a nail that an injury does not explain. Do not wait for a vacation or for the spot to hurt.

Red flags: go to urgent care or call 911 if a growth on the skin bleeds heavily and does not stop with firm pressure. Any bleeding mole that stops on its own still needs an appointment soon.

How a clinician checks a spot

A skin exam is the first step. If a spot looks suspicious, the clinician takes a biopsy, which means removing cells or tissue so they can be viewed under a microscope for signs of cancer. If melanoma is found, further tests such as imaging or a sentinel lymph node biopsy may be used to find out how far it has spread. Cutting out or burning off a mole at home skips this step and can leave you without an answer.

Treatment in general terms

According to the National Cancer Institute, surgery to remove the tumor is the main treatment for all stages of melanoma. Other options depend on the stage and include immunotherapy, which helps the immune system fight cancer, and targeted therapy, which uses drugs to attack specific cancer cells. A cancer team chooses the plan for each person.

Prevention

The CDC says too much ultraviolet exposure from the sun or from tanning beds causes most skin cancers, and the damage builds up over time. The World Health Organization links melanoma risk with intense, occasional sun exposure and with sunburn at an early age.

• Protect your skin from the sun and avoid tanning, as the CDC advises.
• Avoid tanning beds completely.
• Try to prevent sunburn, especially in children and teenagers.
• Ask a dermatologist how often you should have a skin exam if you have several risk factors.

Questions and answers

Sources

1. NCI — Melanoma Treatment (PDQ)
2. NHS — Melanoma skin cancer: symptoms
3. CDC — Skin Cancer
4. CDC — Skin Cancer Risk Factors
5. WHO — Radiation: Ultraviolet (UV) radiation and skin cancer
6. MedlinePlus — Melanoma

Sources checked on 29 October 2026.