About half of all melanomas start with a change in previously normal-looking skin. This usually looks like a dark area or an abnormal new mole that changes over weeks or months. Other melanomas develop from a mole that you already have.
It can be difficult to tell the difference between a melanoma and a normal mole. The following checklist is known as the ABCDE list. It helps explain what to look for.
Photographs are from the website of the National Cancer Institute (cancer.gov).
A – Asymmetry
Most melanomas are likely to be irregular or asymmetrical. Ordinary moles are usually symmetrical (both halves look the same).
The left photograph shows a melanoma with an asymmetrical shape. The right photograph shows a normal mole with no asymmetry.
B – Border
Melanomas are more likely to have a blurred or irregular border with jagged edges. Ordinary moles usually have a well-defined, smooth-edged border.
The left photograph shows a melanoma with an irregular border. The right photograph shows a normal mole with a clear border.
C – Colour
Melanomas tend to be more than one colour. They may have different shades, such as brown mixed with a black, red, pink, white or bluish tint. Normal moles tend to be one shade of brown.
The left photograph shows a melanoma with colour difference. The right photograph shows a normal mole with no colour difference.
D – Diameter (width)
Melanomas are usually more than 6mm wide. Normal moles are not usually bigger than the blunt end of a pencil.
If you have lots of large moles, some of them may be larger than 5mm in diameter. These are likely to have been there for years without change. But it is recommended that people with large moles get them checked by a dermatologist.
The left photograph shows a melanoma with diameter change. The right photograph shows a normal mole with no change in diameter.
E – Evolving (changing)
Look for changes in the size, shape or colour of a mole. The change in shape can include the area becoming raised or dome-shaped.