Melanoma is the most deadly form of skin cancer as it is more likely than any other to spread to other parts of the body.
It is also the least common skin cancer although; over the last 15 years the number of cases has increased by an average of 100%. Worldwide around 132,000 melanomas are now diagnosed each year. They account for just 4% of all skin cancers but are responsible for 79% of deaths from the disease.
Melanoma starts in the pigment producing melanocyte cells in the top layer of the skin known as the epidermis. The cells become cancerous normally due to damage caused by intermittent but very intense exposure to the sun, or repeated sunburn.
In women a melanoma is normally found on the lower legs and arms while in men it is more common on the back.
Melanoma cells usually continue to produce the pigment melanin which is why they look very much like moles. The difference is they can be irregular in shape with ragged edges. Melanomas may be made up of various shades of brown; they may increase in size and be raised above the surface of the skin. Itching or bleeding of the area can also be tell tale signs.
There are several types of melanoma:
Superficial Spreading Melanoma
This is the most common type of melanoma, occurring in about 70% of cases. It is more usual in middle aged people and is likely to be found on the legs, trunk and back, although it can occur anywhere on the body.
It starts off as a flat coloured mole and tends to grow outwards and if removed at this stage there is a very good chance of recovery. If it isn't removed it is likely to grow deeper into the skin and could spread to the lymph nodes which could take the cancer to any other organ of the body.
Lentigo Maligna Melanoma
This form of melanoma is commonly found as a flatish mole or lesion on the face of older people. It is a very slow type of skin cancer and it can take several years to develop.
A melanoma which is more common in middle aged people appearing as a small dark brown lump on the skin's surface. It commonly occurs on the chest or back. It can grow very deep very quickly if not removed.
Acral Lentiginous Melanoma
A type of melanoma which is commonly found on areas of the body that aren't normally exposed to the sun such as the soles of the feet or the palms of the hands.
There are other types of melanoma, although they are very rare, such as subungual melanoma which looks very much like a bruise under the finger or toenails and amelanotic melanoma (in which the melanoma loses its pigment so may only be detectable on detailed examination of the skin).
Melanoma can affect any part of the body. In extremely rare cases it can appear in the mouth, anus, vagina, nasal passages and inside the eye.
If a melanoma is found early enough and removed before the cancer cells have spread there is an excellent chance of recovery - usually about 98%. If it is discovered after the cancer cells have spread then it can be fatal. These cells can spread incredibly quickly to organs such as the brain and the liver as well as to the bones, making the advanced form of the disease very hard to treat.