The ABCDE Rule for Melanoma
The ABCDE rule is a simple guide used to help people recognise features that can occur in melanoma. It is a screening aid, not a way to diagnose a mole yourself.
If you notice a new spot, a spot that looks different from the others on your skin, or a lesion that is changing, itching or bleeding, arrange an assessment by an appropriate healthcare professional.
A — Asymmetry
One half of the spot is unlike the other half.
Many ordinary moles are roughly symmetrical, while a suspicious lesion may have two sides that differ in shape or appearance.
B — Border
Look for an irregular, scalloped, notched or poorly defined border.
A border that is changing or becoming less clearly defined is also worth having assessed.
C — Colour
Melanoma can show colour variation from one part of the lesion to another. Shades may include tan, brown or black and can sometimes include white, red, pink or blue areas.
A changing colour pattern can be important even when the lesion is small.
D — Diameter
Melanomas are often greater than 6 mm across when diagnosed, approximately the width of a pencil eraser, but they can be smaller.
Do not ignore a changing or unusual spot simply because it is under 6 mm.
E — Evolving
Evolving means a spot is changing in size, shape, colour or appearance, or it looks different from the rest of your moles.
Evolving is particularly important because change over time can be a warning sign even when a lesion does not meet every other ABCDE criterion.
The “ugly duckling” sign
Another useful idea is to notice a mole or spot that looks noticeably different from your other moles. Dermatologists sometimes describe this as the “ugly duckling” sign.
A lesion that stands out from the person's usual pattern deserves attention.
Other changes worth checking
Seek medical assessment for a lesion that is:
- new and continuing to grow
- changing in shape or colour
- itching or painful
- bleeding, crusting or oozing without a clear reason
- different from the other spots on your skin
Check more than sun-exposed skin
Melanoma can develop in areas that are easy to miss. A skin check should include the scalp, palms, soles, between the toes and around the nails as well as more obvious sun-exposed areas.
The ABCDE rule does not diagnose melanoma
Most unusual-looking moles are not melanoma, and some melanomas do not fit the classic ABCDE pattern. Diagnosis requires clinical assessment and, when indicated, examination of a tissue sample.
Do not wait for a lesion to meet all five criteria before seeking advice. A new or changing spot can be enough reason to have it checked.
Information on this page is for general education only. It cannot diagnose skin cancer. If you are concerned about a mole, lesion or skin change, seek assessment from a qualified healthcare professional.