A melanoma is a malignant tumour (cancer) that occurs in the skin, often appearing as a new spot on normal skin, or developing from an existing mole.

Risk factors for melanoma include:

  • fair skin (though all ethnic groups can be affected)
  • family history of melanoma or other skin cancers
  • exposure to UV radiation from sunlight (and tanning sunbeds)
  • having severe sunburn in childhood and adolescence
  • having a lot of moles on your body.

The key is doing what you can to prevent further skin damage and sunburn. Have regular skin checks with your doctor and if you notice any darker, growing or changing moles, get it checked straight away. 

If found and treated early, most melanomas are curable.

In New Zealand we have one of the highest rates of melanoma in the world, so do look out for unusual spots or moles and act early.

Where does melanoma occur?

Melanoma occurs most commonly on parts of the body that have been sunburned, but it can appear in skin anywhere on the body.

Melanoma develops from melanocytes, which are the cells that produce melanin, the pigment that gives skin its colour.

Skin cancer formation

Like all body tissues, the skin is made of tiny ‘building blocks’ called cells. These cells can sometimes become cancerous when they have been damaged; for example, by UV (ultraviolet) radiation.

Skin cancers are named after the type of cell they begin to grow from.

The three most common types of skin cancer are basal cell cancer, squamous cell cancer and melanoma.

What do melanomas look like?

Melanomas usually begin as a flat, coloured spot or mole that changes in size, shape, or colour, or becomes raised over months.

A less common type of melanoma (called nodular melanoma) is not flat, and is raised from the start. These melanomas grow quickly, are uniform in colour (have the same colour throughout), and may have no colour.

Melanoma can start in parts of the body other than the skin, but this is rare. The parts of the body that can be affected are: the eye (ocular melanoma), the mouth, vulva or vagina (mucosal melanoma), under fingernails or toenails (subungual melanoma).

Who develops melanoma?

Melanoma is most common in people with fair skin. However, people from ethnic groups with naturally darker skin, for example, Maori, Pacific and Asian peoples, can still get melanoma. Melanoma is diagnosed most often in older adults, but sometimes occurs in younger adults, and occasionally in teenagers. It is rare in children.

Risk factors for melanoma

Risk factors include:

  • fair skin and red or fair hair
  • one or more severe sunburns – especially in childhood and adolescence
  • use of sunbeds, particularly by young people.

High-risk factors include:

  • previous skin cancers, including melanoma
  • a family history of melanoma (in a first-degree relative: parent, brother, sister or child)
  • large, irregularly shaped and unevenly coloured moles called atypical or dysplastic naevi
  • large number of moles
  • people who have had organ transplants
  • some medications - talk to your doctor or pharmacist.

What are the causes of melanoma?

Too much sun, especially sunburn, can cause melanoma. Each time your unprotected skin is exposed to UV radiation from the sun or other sources – such as sunbeds – the UV radiation causes changes to the structure of the cells.

Overexposure to UV radiation causes the skin to become permanently damaged. The damage worsens with more UV radiation.

Sun protection in children

The most important years for sun protection are during childhood and early adult years. Exposure to UV radiation during these years greatly increases the chance of getting melanoma later in life.

Learn more

Credits: Editorial team. Last reviewed: 06 Dec 2017