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Diseases

Skin Cancer (Malignant Skin Melanoma)

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What is Skin Cancer?


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Skin Cancer


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Melanomas are cancers of cells known as ‘melanocytes’ that are present in the skin. The purpose of the melanocytes is to produce a dark pigment called melanin. Melanin is important for protecting DNA (a very complex chemical that determines what a cell does) from the damaging ultraviolet radiation from the sun. Melanin is the primary determining factor in someone’s skin colour – the more melanin in the skin, the darker it will appear.

Sometimes, however, something can go wrong in a melanocyte. It becomes cancerous and grows very quickly, becoming bigger and bigger. The cancerous cells can eventually spread to other parts of the body where they can keep growing, causing damage to the surrounding structures. It is important to be able to recognise the signs of a melanoma while it is still local. If it has not yet spread, there is a better chance of removing all the cancerous cells.

There are actually several different types of melanoma, each with different patterns of growth and different areas that they grow in. That is why it is important for you to see your GP if you are at all worried about any areas of pigmentation on your skin.

Who gets Skin Cancer?

Malignant melanomas are the most serious form of skin cancer, because while they only account for around 4% of skin cancers, they are responsible for 80% of deaths related to skin cancer. Add to this that only 14% of patients in whom the disease has metastasised (spread to other parts of their body) survive for 5 years, and you get a picture of how serious they can be.

Melanoma is also one of the most frequently occurring cancers in Australia. Men have a 1 in 26 chance, and women a 1 in 36 chance, of developing a melanoma before they are 75. The typical age range is between 30-50 years, with the average being 40 years. Skin cancer is rare before the age of 20. The chance of developaing a melanoma increases with age, but it can still occur in younger people.

Predisposing Factors

Two thirds of all melanomas can be attributed to sun exposure. It may seem strange, but people who go out into the sun episodically (e.g. going to the beach every weekend) are actually at a higher risk than people who have had more regular and long-term exposure (e.g. a farmer).

You are more at risk if you burn very easily and are particularly ‘sun sensitive’. This is thought to be due to the damage that is caused to the skin by the ultraviolet radiation of the sun.

There are other strong risk factors for melanoma. A family history of melanoma puts you at much higher risk than other people. Also, if you have a lot of moles or have previously had a melanoma, there is a higher risk of melanoma. If you are on immunosuppressive medication then your body is less able to fight off the cancerous cells and you are more likely to get a melanoma.

Progression

A melanoma will initially be confined to the surface of the skin, with the melanocytes multiplying and forming an expanding area of dark pigmentation. If left untreated, it can grow vertically (that is, into the skin rather than across it) and get into some of the deeper structures. Some of the cells can then break off the initial melanoma and get into the blood stream or the lymphatic system. These provide ‘pathways’ down which the cells can spread to other parts of the body. Sometimes ‘satellite’ melanomas can be seen, where they begin to appear in small islands away from the original site. The cells can spread to the lymph nodes, where they can form small hard lumps of dense cells. They can then also spread to other organs of the body, particularly those with high blood supply such as the brain, the bones and the liver. The cancer can cause large amounts of damage in these locations.

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Article Dates:

calendar icon Created: 6/8/2002 calendar icon Modified: 9/6/2008 calendar icon Reviewed: 12/6/2007