Most moles are harmless, and no checklist can diagnose melanoma. The ABCDE method is a practical way to notice features worth discussing with a healthcare professional. It is most useful when you compare a spot with the rest of your skin and with how it looked before.
A simple five-part check
A — Asymmetry
One half of the spot does not match the other half in shape or appearance.
B — Border
The edge looks irregular, scalloped, notched, blurred, or poorly defined rather than smooth and even.
C — Color
Color varies from one area to another. A spot may contain different shades of tan, brown, or black, and sometimes areas of white, red, or blue.
D — Diameter
Melanomas are often larger than 6 millimeters when diagnosed—about the width of a pencil eraser—but they can be smaller. Size alone cannot rule melanoma in or out.
E — Evolving
The spot is changing in size, shape, color, texture, or symptoms over time. It may also look noticeably different from your other spots. Evolution is especially important because a change can matter even when the other letters do not fit neatly.
Changes that do not fit the ABCDEs
Skin cancer does not always look like a classic dark mole. Contact a healthcare professional about a skin change such as:
- A new growth or a spot that looks different from the others.
- A sore that does not heal, or heals and then returns.
- A spot that changes, itches, bleeds, oozes, or becomes tender.
- A persistent rough or scaly patch.
- A new or changing dark streak beneath a fingernail or toenail.
Check everywhere, not only sun-exposed areas. Skin cancer can appear on the scalp, palms, soles, between the toes, beneath nails, and in other places that receive little sun.
What to do if you notice something
- Record the change. A dated photo in consistent lighting can help you describe what you noticed, but it should not delay care.
- Contact a dermatologist or another qualified healthcare professional promptly, especially for a new or changing spot, a non-healing sore, or bleeding.
- Do not rely on a photograph, app, or visual checklist for a diagnosis. A skin biopsy examined under a microscope is required to confirm skin cancer.
The bottom line
The ABCDEs give you a useful vocabulary for noticing change. They are not a pass-or-fail test. If a spot concerns you—even if it does not meet every ABCDE—ask a qualified clinician to assess it.
This article is for general education only and is not medical advice, diagnosis, or treatment. Seek urgent medical care for any rapidly worsening or otherwise urgent health concern.