Malignant melanoma is a cancer which usually starts in the skin, either in a mole or in normal-looking skin. Although the number of people who develop melanoma is rising, it is still an uncommon type of cancer. About 8,100 people in the UK are diagnosed with melanoma each year.

Melanoma develops from cells in the skin known as melanocytes. Melanocytes give the skin its colour. In melanoma the melanocytes start to grow and divide more quickly than usual and start to spread into the surrounding surface layers of skin. This happens slowly over some months. If the melanoma is found at this early stage, it can be removed with surgery. Most people with melanoma less than 1mm in depth are cured. In the UK, most melanomas are found at this early stage.

If the melanoma is not removed, the cells can begin to grow down into the deeper layers of the skin. These layers contain tiny blood vessels and lymph channels. If the melanoma cells go into the blood vessels or lymph channels, they can travel to other parts of the body in the blood stream or lymph system.