What is skin cancer?
Skin cancer is the uncontrolled growth of abnormal cells in the skin.
The skin is the largest organ of the body. It acts as a barrier to protect the body from injury, control body temperature and prevent loss of body fluids. The two main layers of the skin are the epidermis and dermis. Below these is a layer of fatty tissue.
This is the top, outer layer of the skin. It is made up of several cell types:
These flat cells are packed tightly together to make up the top layer of skin and form the thickest layer of the epidermis. Over time, our body sheds these dead skin cells.
These block-like cells make up the lower layer of the epidermis and multiply constantly. As they age, they move up within the epidermis and flatten out to form squamous cells.
These cells sit between the basal cells and produce a dark pigment called melanin, the substance that gives skin its colour. When skin is exposed to ultraviolet (UV) radiation, melanocytes make extra melanin to protect the skin from getting burnt. Melanoma develops in melanocytes. Melanocytes are also in non-cancerous spots on the skin called moles or naevi.
This layer of the skin sits below the epidermis. The dermis contains the roots of hairs (follicles), sweat glands, blood vessels, lymph vessels, and nerves. All of these are held in place by collagen and elastin, the proteins that gives skin its strength and elasticity.
What types are there?
The three main types of skin cancer are basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and melanoma. BCC and SCC are also called non-melanoma or keratinocytic skin cancers. See signs to look for.
Rare types of skin cancer include Merkel cell carcinoma and angiosarcoma, but they are treated differently from BCC and SCC. Call Cancer Council 13 11 20 to find out more about rarer skin cancers.
Basal cell carcinoma (BCC)
This starts in the lower layer of the epidermis. It makes up about 70% of non-melanoma skin cancers.
BCC grows slowly over months or years and rarely spreads to other parts of the body. The earlier a BCC is diagnosed, the easier it is to treat. If left untreated it can grow deeper into the skin and damage nearby tissue, making treatment more difficult.
Having one BCC increases the risk of getting another. It is possible to have more than one BCC at the same time on different parts of the body.
Squamous cell carcinoma (SCC)
This starts in the upper layer of the epidermis. It accounts for about 30% of non-melanoma skin cancers.
SCC may spread to other parts of the body if left untreated. SCC on the lips and ears is more likely to spread and should be examined by a doctor as soon as possible.
Squamous cell carcinoma in situ, or Bowen disease, is an early form of skin cancer that begins in the top layer of the skin (epidermis). It looks like a red, scaly patch and can develop into invasive squamous cell carcinoma if left untreated. The diagnosis and treatment of squamous cell carcinoma in situ is similar to BCC and SCC.
This starts in the melanocyte cells of the skin. Although it is not as common as BCC and SCC, melanoma is considered the most serious type of skin cancer. This is because it is more likely to spread to other parts of the body, such as the lymph nodes, lungs, liver, brain and bones, especially if not detected early.
Australia and New Zealand have the highest rates of melanoma in the world.
For more information, see Understanding Melanoma or call Cancer Council 13 11 20. The Melanoma Institute Australia website at melanoma.org.au also has more details.
The signs of skin cancer
Non-melanoma skin cancers
- usually develops on sun-exposed areas of the body, such as the head, face, neck, shoulders, back, lower arms and lower legs, but it can occur anywhere on the body
- may appear as a pearl-coloured lump or as a slightly scaly area that is shiny and pale or bright pink in colour, although some BCCs have a darker colour
- may bleed and become inflamed; some BCCs seem to heal then become inflamed again
- tends to grow slowly over months or years
- usually appears on parts of the body most often exposed to the sun, such as the head, neck, hands, forearms and lower legs, but it can start anywhere on the body
- may bleed and become inflamed, and is often tender to touch
- often appears as a thickened red, scaly or crusted spot or rapidly growing lump
- is more common as you get older
- tends to grow quickly over several weeks or months
- can appear as a new or existing spot on the body that changes size, shape or colour over several weeks or months
- often has an irregular edge and either a flat or raised surface
- may be more than one colour (brown, black, blue, red, white, light grey, pink or skincoloured)
The signs of non-cancerous skin spots
- brown, black or skin-coloured and usually round or oval
Warning signs of skin cancer
- mole with an irregular shape and uneven colour
- flat, scaly spot that feels rough and often skin-coloured or red
What about other skin spots?
Some spots that appear on the skin are not cancerous.
A mole (naevus) is a normal growth on the skin that develops when the skin's pigment-producing cells (melanocytes) grow in groups.
Moles are very common. Some people have many moles on their body – this can run in families. Overexposure to the sun, especially in childhood, can also increase the number of moles.
People with many dysplastic naevi have a greater risk of developing melanoma.
Sunspots (solar or actinic keratoses)
Anyone can develop sunspots, but they occur more often in people over 40, generally on skin that's frequently exposed to the sun, such as the head, neck, hands, forearms and legs.
They are a warning sign that the skin has had too much sun exposure, increasing the risk of skin cancer.
What causes skin cancer?
The main cause of all types of skin cancer is overexposure to UV radiation. When unprotected skin is exposed to UV radiation, the structure and behaviour of the cells can change.
UV radiation is produced by the sun, but it can also come from artificial sources, such as the lights used in solariums (sun beds). While commercial sun beds are now banned in Australia, people who used a solarium before age 35 have an almost 60% greater risk of melanoma.
Most parts of Australia have high levels of UV radiation all year round. UV radiation cannot be seen or felt and it is not related to temperature, but it can cause:
- premature skin ageing
- damage to skin cells, which can lead to skin cancer.
To help understand when to protect yourself from the sun, see The UV Index and sun protection times.
Who is at risk?
Anyone can develop skin cancer, but it's more common the older you are. The risk is also higher in people who have:
- fair or freckled skin, especially if it burns easily and doesn't tan
- red or fair hair and light-coloured eyes (blue or green)
- experienced short, intense periods of exposure to UV
- radiation, e.g. on weekends or holidays or when playing sport, especially if it caused sunburn
- actively tanned or used solariums
- worked outdoors
- a weakened immune system, which could be caused by taking certain medicines after an organ transplant (immunosuppressants) or being HIV-positive
- lots of moles on their body
- moles with an irregular shape and uneven colour ( dysplastic naevi)
- a previous or family history of skin cancer
- certain skin conditions such as sunspots.
People with olive or very dark skin naturally have more protection against UV radiation because their skin produces more melanin than fair-skinned people. However, they can still develop skin cancer.
Slip, slop, slap, seek and slide to protect your skin from overexposure to the sun and sun damage.
How common is skin cancer?
Australia has one of the highest rates of skin cancer in the
world. Skin cancer is the most common cancer diagnosed in Australia. About two in three Australians will be diagnosed with some form of skin cancer before the age of 70. 3
Almost 770,000 new cases of BCC and SCC are treated each year. BCC can develop in young people, but it is more common in people over 40. SCC occurs mostly in people over 50.
More than 12,000 people are diagnosed with melanoma each year. It is among the five most commonly diagnosed cancers in all age groups. 4
How do I spot a skin cancer?
Skin cancers don't all look the same, but there are signs to look out for, including:
- a spot that is different from other spots on the skin
- a spot that has changed size, shape, colour or texture
- a sore that doesn't heal
- a sore that is itchy or bleeds.
There is no set guideline on how often to check for skin cancer, but checking your skin regularly will help you notice any new or changing spots. If you have previously had a skin cancer or are at greater risk of developing skin cancer, ask your doctor how often to check your skin.
How to check your skin
In a room with good light, undress completely and use a full-length mirror to check your whole body. To check areas that are difficult to see, you can use a handheld mirror or ask someone to help you.
- Face and scalp
- Neck and shoulders
- Front and back of your arm, including armpit
- Front and back of hands, between your fingers and under the fingernails
- Between toes and on soles of feet
If you notice anything new or changes to your skin, make an appointment with your GP or dermatologist straightaway. Skin cancers that are found and treated early need less invasive treatment and have a better outcome (prognosis). Visit SunSmart's checking for skin cancer for more information about checking your skin.
Expert content reviewers:
Dr Judy Cole, Consultant Dermatologist, St John of God Dermatology, WA; Irena Brozek, Research and Development Officer, Cancer Council NSW; Shannon Jones, SunSmart Health Professionals Coordinator, Cancer Council Victoria, VIC; David Lemon, Consumer; Dr Margaret Oziemski, Dermatologist, QLD; Megan Trewhella, Nurse Coordinator, Melanoma and Skin Service, Peter MacCallum Cancer Centre, VIC; Chelsey Upston, 13 11 20 Clinical Nurse Specialist, Cancer Council Victoria, VIC.
3. MP Staples et al., “Non-melanoma skin cancer in Australia: the 2002 national survey and trends since 1985”, Medical Journal of Australia, vol. 184, no. 1, 2006, pp. 6–10.
4. Australian Institute of Health and Welfare (AIHW), Cancer in Australia 2017, AIHW, Canberra, 2017.