The short answer
Melanoma often shows up as a new or changing mole. The ABCDE rule — Asymmetry, Border, Color, Diameter, Evolving — helps spot warning signs. Found early, melanoma is very treatable.
Melanoma often appears as a new mole or a change in an existing mole.
The ABCDE rule helps: Asymmetry, Border, Color, Diameter, Evolving.
A spot that looks different from your others (the 'ugly duckling') is worth checking.
Melanoma can also appear as a sore that does not heal or a dark streak under a nail.
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The full explanation.
The simple version
Melanoma is the most serious type of skin cancer, but it is very treatable when found early. It often shows up as a new mole or a change in an existing one, so knowing the warning signs helps you catch it early.
The ABCDE rule
Watch for these signs in a mole:
- A — Asymmetry: one half does not match the other
- B — Border: ragged or irregular edges
- C — Color: more than one shade or uneven color
- D — Diameter: larger than a pencil eraser
- E — Evolving: changing in size, shape, or color
The ugly duckling
Another helpful clue is the 'ugly duckling' sign: a spot that looks different from your other moles. A mole that stands out from the rest is worth checking, even if it does not meet every ABCDE sign.
A mole that is changing, or that looks different from your others, should be checked.
When to see a doctor
See a doctor or dermatologist for any new or changing mole, a spot that stands out, a sore that does not heal, or a dark streak under a nail. Early melanoma is very treatable.
Words to know
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Common questions
▸What does melanoma look like?
It often appears as a new mole or a change in an existing one. The ABCDE rule describes warning signs: Asymmetry, irregular Border, uneven Color, large Diameter, and Evolving (changing over time).
▸What is the 'ugly duckling' sign?
It is a spot that looks different from your other moles. A mole that stands out from the rest is worth having checked, even if it does not meet every ABCDE sign.
▸Where can melanoma appear?
It can appear anywhere, including areas with little sun exposure, and sometimes as a dark streak under a nail or a sore that does not heal.
▸Is melanoma treatable?
Yes, especially when found early. Early melanoma is very treatable, which is why checking new or changing spots matters.
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