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 and the older cells move upwards in the epidermis. When they flatten out and form a layer they become squamous cells. The top layer of your skin is made up of dead skin cells that eventually fall off.
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:
Melanoma develops from melanocytes (pigment cells). It usually occurs on parts of the body that have been overexposed to the sun. However, melanoma can also start in a part of the skin or an other part of the body that's never been exposed to the sun, such as the nervous system, eye and mucous membrane (lining of the mouth and digestive tract).
Melanoma is the least common skin cancer but it's the most serious because it can spread to other parts of the body.
If found early, melanoma is often curable. If detected later, it may have grown down deeper into the dermis where it may spread.
Skin melanomas are called cutaneous melanomas. Cutaneous melanomas are categorised by how thick they are, how far they've spread and the way they look.
This is when the abnormal cancer cells are only in the epidermis and haven't penetrated into the dermis.
Australia and New Zealand have the highest rates of melanoma in the world. More than 10,000 people are diagnosed with melanoma in Australia every year.
Melanoma of the skin is the fourth most common cancer in both men and women. It accounts for 10% of all cancer diagnoses. One in 19 Australians will be diagnosed with melanoma before age 85.
It's the most common type of cancer in young Australians aged 15 to 44 (20% of all cases).
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 what they do.
Exposure 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 will help prevent skin cancer at whatever age it's used.
Sometimes melanoma happens by chance and isn't linked to sun exposure, but this is uncommon.
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, in a small number of people (5% to 10%), melanoma may be caused by an inherited faulty gene.
If you're concerned that you have 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 Helpline on 13 11 20.
The following factors may increase a person's risk of developing melanoma:
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's normal for new moles to appear and change during childhood and pregnancy. However, all adults who have a new mole should get it examined. Even if you've had a mole checked before and it was assessed as benign, keep an eye on it because it could change in the future. Talk to your doctor immediately about any changes.
Information reviewed by: Prof Grant McArthur, Consultant Medical Oncologist, Head of the Translational Research Group and Head of the Molecular Oncology Laboratory, Peter MacCallum Cancer Centre, VIC; Jay Allen, Consumer and Community Coordinator, Melanoma Institute Australia, NSW; Annie Angle, Cancer Council Helpline Nurse, Cancer Council Victoria; Prof Michael P Brown, Director, Cancer Clinical Trials Unit, Senior Medical Oncologist, Royal Adelaide Cancer Centre, SA; Dr Vanessa Estall, Head Radiation Oncologist, Melanoma and Skin Service, Peter MacCallum Cancer Centre, VIC; Clinton Heal, Consumer and CEO and Founder of Melanoma WA; Prof John Thompson, Professor of Melanoma and Surgical Oncology at the University of Sydney and Director, Melanoma Institute Australia, NSW; and members of the SunSmart Victoria team.