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Symptoms - Skin cancer (melanoma)

The first sign of a melanoma is often a new mole or a change in the appearance of an existing mole.

Normal moles are usually round or oval, with a smooth edge, and no bigger than 6mm (1/4 inch) in diameter.

normal mole on skin
Picture of a normal mole

See your GP as soon as possible if you notice changes in a mole, freckle or patch of skin, particularly if the changes happen over a few weeks or months.

melanoma on skin
Picture of a melanoma

Signs to look out for include a mole that's:

  • getting bigger
  • changing shape
  • changing colour
  • bleeding or becoming crusty
  • itchy or sore

Melanomas can appear anywhere on your body, but they most commonly appear on the back in men and on the legs in women. They can also develop underneath a nail, on the sole of the foot, in the mouth, or in the genital areas, but these types of melanoma are rare.

ABCDE of moles

Most moles are harmless, but in a few rare cases they can develop into an aggressive form of skin cancer called malignant melanoma.

The ABCDE checklist can help you tell the difference between a normal mole and a melanoma:

A: Asymmetrical

Melanomas are asymmetrical. They have two very different halves and are an irregular shape.

asymmetrical melanoma on skin
Picture showing an asymmetrical melanoma

B: Border

Melanomas have a notched or ragged border. 

Picture showing notched or ragged border of a melanoma
Picture showing notched or ragged border of a melanoma

C: Colours

Melanomas will be a mix of two or more colours.

Picture showing colours of a melanoma
Picture showing colours of a melanoma

D: Diameter

Melanomas are larger than 6mm (1/4 inch) in diameter.

picture showing size of melanoma against a ruler
Picture showing size of melanoma against a ruler

E: Enlargement or elevation

A mole that changes size over time is more likely to be a melanoma. A melanoma usually gets bigger and is raised or elevated above the surface level of the skin.

picture showing an elevated or raised melanoma
Picture showing an elevated or raised melanoma

Melanoma of the eye

In rare cases, melanoma can develop in the eye. It develops from pigment-producing cells called melanocytes.

Eye melanoma usually affects the eyeball. The most common type is uveal or choroidal melanoma, which occurs at the back of the eye. Very rarely it can occur on the conjunctiva (the thin layer of tissue that covers the front of the eye) or in the iris (the coloured part of the eye).

Noticing a dark spot or changes in vision can be signs of eye melanoma, although it's more likely to be diagnosed during a routine eye examination.

Content supplied by the NHS and adapted for Ireland by the HSE

Page last reviewed: 9 July 2019
Next review due: 9 July 2022

This project has received funding from the Government of Ireland’s Sláintecare Integration Fund 2019 under Grant Agreement Number 123.