The ABCDE Rule: A Guide to Checking Your Moles
A simple, memorable self-examination guide used by skin cancer specialists worldwide — written for patients by Mr Masha Singh.
The ABCDE rule is a simple mnemonic designed to help patients identify mole features that may need specialist assessment. No self-check replaces professional examination, but knowing these signs helps you spot concerning changes early — when treatment is most effective.
Melanoma, the most serious form of skin cancer, is highly curable when diagnosed early. The five-year survival rate for early-stage melanoma exceeds 98%, compared with around 27% for advanced disease. The single most important factor determining outcome is how early the diagnosis is made — and that often depends on you noticing something and acting on it.
Work through each letter below when examining a mole. If any one feature is present, the mole deserves a professional opinion. Two or more features make specialist review essential.
A, B, C, D, E
If you draw a line through the middle of the mole, both halves should match. Asymmetry, where one half looks different from the other, can be a warning sign.
Healthy moles have smooth, well-defined borders. Uneven, ragged, notched, blurred or scalloped edges may be a concern.
Benign moles are usually a single shade of brown. Variations in colour — black, blue, red, white, or multiple shades of brown — warrant assessment.
Most melanomas are larger than 6mm (the size of a pencil eraser) when diagnosed, but they can be smaller. Any mole that appears larger than your others should be reviewed.
The single most important feature. Any mole that is CHANGING in size, shape, colour, elevation, or developing new symptoms (itching, bleeding, crusting) should be seen urgently.
The “Ugly Duckling” Sign
Most of your moles will look similar to each other — they share a family resemblance in size, shape and shade. The “ugly duckling” is a mole that stands out because it looks different from all your others. This alone can be a useful warning sign, even if none of the ABCDE criteria are clearly met.
Trust your eye. If one mole simply doesn't look like the rest of your moles — if it is the odd one out when you scan across your skin — that is enough reason to have it examined. Specialists use this principle routinely when screening patients, and it is one of the most effective ways to spot an early melanoma amongst many benign moles.
Other Warning Signs
Not every concerning skin lesion is a classic mole, and not every skin cancer follows the ABCDE pattern. Other features that should prompt assessment include:
- Any new lesion appearing after age 40. Most moles appear in the first three decades of life. A genuinely new pigmented lesion in middle age should be taken seriously.
- A mole or lesion that itches, bleeds or crusts. These symptoms are rarely normal in an established mole and always warrant review.
- A sore or scab that doesn't heal within 4 weeks. Non-healing lesions can represent basal cell or squamous cell skin cancers, particularly on sun-exposed skin.
- A change in a long-standing mole. Even a mole that has been present for decades can transform. Change is the most important sign of all.
- Any lesion you are simply worried about. Trust your instincts. Patients are often the first to notice something wrong — and a quick specialist assessment either reassures you or catches a problem early.
How to Check Your Own Skin
A monthly self-examination takes ten minutes and is one of the most valuable things you can do for your skin health. Here is how to do it well:
- Check your skin monthly. A regular rhythm — the first of the month, for example — helps you notice change rather than examining fresh each time.
- Use a full-length mirror plus a handheld mirror. In good lighting, systematically check every part of your skin. The handheld mirror is essential for the back, shoulders and buttocks.
- Ask a partner or family member to check your back and scalp. These are the areas you cannot easily see yourself — and they are common sites for melanoma.
- Take photographs to track changes over time. A dated photo of a mole on your phone is the simplest way to detect subtle evolution over months and years. Compare today's mole against last year's photograph.
- Check all skin — including soles, palms, between toes, under nails and genital skin. Skin cancer can arise anywhere, including sun-protected sites. A thorough self-check is a complete self-check.
Worried About a Mole?
If any of the ABCDE features apply to a mole on your skin — or if you simply want the reassurance of a professional opinion — book a private mole check with Mr Singh, a highly trained and experienced skin cancer specialist.