Melanoma

Tuesday 30 June, 2009

Reviewed: Prof. John Kelly, Dermatologist; 
Mr David Speakman, Head, Melanoma & Skin Service, Peter Mac

On this page: The skin | Skin cancer | Melanoma | Causes of melanoma | How common is melanoma?

The skin

The skin has many important functions. It protects us from injury, cools us when we get too hot and prevents us from becoming dehydrated.

The skin has 2 main layers. The top layer is called the epidermis. This layer contains, among other things, melanocytes-cells that produce melanin, the substance that gives skin its colour. The layer underneath the epidermis is called the dermis. The dermis contains the roots of hairs, glands that make sweat and oil, blood and lymph vessels and nerves.

A diagram of the skin structure

Skin cancer

Like all body tissues, the skin is made of tiny ‘building blocks' called cells. These cells can sometimes become cancerous. One cause is too much exposure to ultraviolet (UV) radiation.

The epidermis contains 3 different types of cells:

  1. squamous cells,
  2. basal cells and
  3. melanocytes.

Skin cancers are named after the type of cell they start from. The 3 main types of skin cancer are basal cell cancer, squamous cell cancer and melanoma, which is the most serious skin cancer. 

Melanoma

Melanoma develops from melanocytes (pigment cells). These cells are the cause of freckles and moles on the skin and produce the colour of a suntan.

Melanoma usually occurs on parts of the body that have been sunburned. However, melanomas can sometimes start in parts of the skin or other parts of the body that have never been exposed to the sun.

Melanoma can grow quickly. If detected early, most melanomas are curable. If they're not detected until later, they can become more serious and may spread to other parts of the body. A melanoma may appear as a new spot on normal skin, or develop from an existing mole.

Melanomas usually begin as a flat spot that changes in size or shape or colour over months. While they remain flat they are generally curable. They usually remain flat for six to 12 months. Later, melanomas become bigger, irregular in shape and often darker in colour.

A less common type of melanoma (called nodular melanoma) is not flat, but is raised from the start. These melanomas are often pink or red, and grow quickly. Not all melanomas are dark or black in colour.

Causes of melanoma

Melanoma and other skin cancers generally develop because of too much exposure to UV radiation. Each time unprotected skin is exposed to the sun's UV radiation or other sources of UV radiation, such as solariums, changes take place in the structure of the cells. Too much UV radiation causes the skin to become permanently damaged. The damage increases with each exposure.

Melanoma is not contagious: you can't catch it from someone else.

People at increased risk of melanoma have one or more of the following:

  • fair skin that burns easily and does not tan
  • a fait complexion
  • lots of moles on the skin
  • a number of large, irregularly shaped and unevenly coloured moles (called dysplastic naevi)
  • previous melanomas
  • a history of many sunburns
  • other people in the family who have had melanoma (a ‘family history')
  • being older (risk increases with age).

Sunburn and too much exposure to UV radiation during childhood greatly increase the risk of melanoma.

How common is melanoma?

Australia has the highest rate of skin cancer in the world. Each year over 2100 people in Victoria are diagnosed with melanoma.

Melanoma is more common in people with fair complexions than people with naturally darker skins. Melanoma is diagnosed more often in older adults. It sometimes occurs in younger adults and teenagers. It's rarely seen in children.

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