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What is melanoma?

Melanoma is a type of skin cancer. It develops in the skin cells called melanocytes and usually occurs on parts of the body that have been overexposed to the sun. Rare melanomas can also start inside the eye or in a part of the skin or body that has never been exposed to the sun, such as the nervous system, mucous membrane (lining of the mouth, digestive tract, etc), soles of the feet, palms, and under the nails.

Although it is one of the less common types of skin cancer, melanoma is considered the most serious because it is more likely to spread to other parts of the body, especially if not detected early. The earlier melanoma is found, the more successful treatment is likely to be.

Australia and New Zealand have the highest rates of melanoma in the world. More than 13,000 people are diagnosed with melanoma in Australia every year. Melanoma is the third most common cancer in both men and women (excluding non-melanoma skin cancers). One in 13 men and 1 in 22 women will be diagnosed with melanoma before age 85.

What are the different types of melanoma?

Melanoma of the skin is known as cutaneous melanoma. The major subtypes are:

Superficial spreading melanoma – This makes up 55–60% of all melanomas. It is more common in younger people and is often related to a pattern of irregular high sun exposure, including episodes of sunburn. It can start as a new brown or black spot that grows on the surface of the skin, or an existing spot, freckle or mole that changes size, colour or shape. It can develop on any part of the body but especially the trunk. This type of melanoma often grows slowly and becomes more dangerous when it invades the lower layer of the skin (dermis).

Nodular melanoma – This type makes up about 10–15% of melanomas. It usually appears as a round, raised lump (nodule) on the surface of the skin that is pink, red, brown or black and feels firm to touch. It may develop a crusty surface that bleeds easily. Nodular melanoma is most commonly found in older people on sun-damaged skin on the head and neck. It is a fast-growing and aggressive form of melanoma, spreading quickly into the lower layer of the skin (dermis).

Lentigo maligna melanoma – This type of melanoma is most common in older people. It makes up about 10–15% of melanomas and begins as a large freckle (lentigo maligna) in an area of sun-damaged skin, such as the face, ears, neck and head. It may grow slowly and superficially over many years before it penetrates more deeply into the skin.

Acral lentiginous melanoma – This is a rare type of melanoma (about 1–2% of all cases). It is most commonly found on the skin on the soles of the feet or palms of the hands, or under the fingernails or toenails. It commonly appears as a colourless or lightly pigmented area, which can be mistaken for a stain or bruise. In the nails, it most often presents as a long streak of pigment in the nail. It tends to grow slowly before becoming invasive.

Desmoplastic melanoma – This is another rare type of melanoma (about 1% of cases). It often appears on the head or neck of sun-damaged skin. Desmoplastic melanoma presents as a firm, growing frequently skin-coloured lump, sometimes described as scar-like. Some have a patch of overlying pigmentation, and can be difficult to diagnose.

Some rarer types of melanoma start in parts of the body other than the skin. Mucosal melanoma can start in the tissues in the mouth, anus, urethra, vagina or nasal passages. Ocular melanoma can start inside the eye. Melanoma can also start in the central nervous system.

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Understanding Melanoma

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