The skin is the largest organ in the body. It covers the body, protecting it from injury, regulating its temperature and preventing it from becoming dehydrated. Skin, like all other body tissues, is made up of cells. It has two main layers called the epidermis and the dermis.
The epidermis is the top, outer layer of the skin. It contains three different kinds of cells:
Basal cells multiply constantly. As they age, they move upwards in the epidermis and flatten out to form a new layer, becoming squamous cells. These cells eventually die and form the top layer of your skin. Over time our body sheds these dead skin cells.
The dermis is the layer underneath the epidermis. It contains the roots of hairs, sweat glands, blood vessels, lymph vessels and nerves.
When skin is exposed to the sun, melanocytes make extra melanin to protect the skin from getting burnt. This is what causes skin to tan. Melanocytes are also in non-cancerous (benign) spots on the skin called moles or naevi. Most moles are brown, tan or pink in colour and round in shape.
Melanoma is a type of skin cancer. There are three main types of skin cancer that are named after the cells that are affected: squamous cell carcinoma (SCC), basal cell carcinoma (BCC) and melanoma. Melanoma develops from the melanocytes (pigment cells).
It usually occurs on parts of the body that have been overexposed to the sun. However, rare melanomas can also start in a part of the skin or another part of the body that has never been exposed to the sun, such as the nervous system, eye and mucous membrane (lining of the mouth and digestive tract), as well as under the feet and nails.
Melanoma is one of the least common skin cancers. However, it is one of the most serious types because it is more likely to spread to other parts of the body, especially if not detected early. If melanoma is found early, treatment is often successful.
Skin melanomas (cutaneous melanomas) are categorised by their appearance, thickness and how far they have spread.
This is the most common type of melanoma, making up almost 50% of all cases. It starts as a brown or black spot that spreads across the outer layer of the skin (epidermis). This type of melanoma becomes dangerous when it invades the lower layer of the skin (dermis).
This type makes up about 10% of melanomas. It is usually a raised lump on the surface of the skin that is often red, pink, brown or black and feels firm to touch. It is a fast growing and aggressive form of melanoma, so if suspected it is important to see your GP (general practitioner) without delay.
This type of melanoma is most common in older people. It makes up about 10% of melanomas and begins as a large freckle (lentigo maligna) in an area of skin that has had a lot of sun exposure, such as the face, ears, neck and head. It may grow slowly and superficially over many years until it penetrates more deeply into the skin.
This is an uncommon type of melanoma that is most commonly found on the palms of the hands, soles of the feet or under the fingernails or toenails. These commonly present as a lightly pigmented, sometimes warty area and do not respond to treatments for warts or tinea. In the nails, they most often present as a long streak of pigment in the nail or discolouration in the skin around the nail.
This is another uncommon type of melanoma that presents as a firm, progressively growing lump, often on the head or neck. Many are skin-coloured and not pigmented.
There are some other rarer types of melanoma, which start in the eyes, nervous system, anus, genital tract (urethra and vagina) and tissues that line the inside of the nose.
This is when the abnormal cancer cells are only in the epidermis and have not penetrated into the dermis.
Australia and New Zealand have the highest rates of melanoma in the world. Over 12,500 people are estimated to be diagnosed with melanoma in Australia every year.
Melanoma is the third most common cancer in both men and women. It accounts for 10% of all cancer diagnoses. One in 18 Australians will be diagnosed with melanoma before age 85.
It is the most common type of cancer in young Australians aged 15–29, making up more than 25% of all cancer cases in this age group.
Melanoma can occur anywhere on the body. In men, it is more common on the trunk, whereas women get more melanomas on their legs.
Melanoma can vary greatly in the way it looks. The first sign of a melanoma is usually a new spot or a change in an existing mole.
It is normal for new moles to appear and change during childhood and teenage years. However, all adults who develop a new mole should see their doctor to get it examined. Even if you have had a mole checked before and it was benign, keep an eye on it because it could change in the future. Talk to your doctor immediately about any changes.
The main cause of all types of skin cancers is exposure to ultraviolet (UV) radiation from the sun or another source, such as a solarium tanning machine. Each time your unprotected skin is exposed to UV radiation, it changes the structure of cells and affects how they behave.
Overexposure to UV radiation permanently damages the skin. This damage adds up over time. The most important years for sun protection are during childhood. However, increased protection against sun exposure is important and will help prevent skin cancer at any age.International research shows that people who first use tanning machines (solariums) before the age of 35 have a 59% higher risk of developing melanoma.
Sometimes melanoma runs in families. For most people this is due to factors such as similar skin type or too much sun exposure in childhood. However, approximately 7% of melanomas may be caused by an inherited faulty gene. Some of these genes have been identified.
The signs that melanoma could be due to an inherited faulty gene include:
People who have a strong family history of melanoma should monitor their own skin and have their skin checked by their GP or skin cancer specialist at least annually from their early twenties. New moles after this age should be investigated.
If you are concerned about your family risk factors, talk to your doctor about having regular skin checks or ask for a referral to a family cancer clinic. To find out more call Cancer Council 13 11 20.
Anyone can develop melanoma. However, the following factors may increase a person’s risk:
Some people have skin that is more sensitive to UV radiation. This includes people who have pale, fair or freckled skin; skin that burns easily and doesn’t tan; and people with light-coloured eyes or fair or red hair.
Adults with more than 10 moles on their arms and more than 100 on their body have an increased risk
Too much sun exposure during childhood and adolescence greatly increases the chance of getting melanoma in later life because damaged cells have more time to develop into cancer.
Studies show that people who move after childhood from low to high UV radiation countries, such as from England to Australia, develop melanoma at a lower rate than people born in Australia.
Melanoma risk is related to the pattern of UV exposure and not just the amount. People with occasional high UV exposure and sunburn, such as on weekends and holidays, are at increased risk.
Melanoma is more common in people over 50 years of age. However, it is the most commonly diagnosed cancer in 15–29 year olds.
People with a previous melanoma or other type of skin cancer (BCC or SCC) have an increased risk. Family history – People with a strong family history of melanoma have an increased risk.
Reviewed by: Prof Bryan Burmeister, Director of Radiation Oncology, Princess Alexandra Hospital, QLD; Dr Victoria Atkinson, Senior Medical Oncologist, Division of Cancer Services, Princess Alexandra Hospital, QLD; Assoc Prof John Kelly, Head of Victorian Melanoma Service VIC; Dr Mark Hanikeri, Director WA Melanoma Advisory Service, Plastic and Reconstructive Surgeon, WA Plastic Surgery Centre WA; Lydia Visintin, Clinical Nurse Consultant, Melanoma Institute Australia NSW; Carol Hargreaves, 13 11 20 consultant, Cancer Council NSW; Julie Fraser, Peer Support Volunteer, Cancer Council QLD ; Susanna Cramb, Viertel Cancer Research Centre, Cancer Council QLD.