There are three main types of skin cancer: basal cell carcinoma, squamous cell carcinoma and malignant melanoma.
Basal cell carcinoma
Basal cell carcinoma, or BCC, is a cancer of the basal cells at the bottom of the epidermis. It is sometimes called a rodent ulcer. It’s very common. About 75% of all skin cancers in the UK are BCCs. Most BCCs are very slow-growing and almost never spread to other parts of the body.
When BCCs are treated at an early stage, they are usually completely cured. However, some BCCs are aggressive, and, if left to grow, they may spread into the deeper layers of the skin and sometimes to the bones. This can make treatment difficult.
A small number of BCCs may come back in the same area of skin after treatment. This is known as a local recurrence.
Squamous cell carcinoma
Squamous cell carcinoma, or SCC, is a cancer of the keratinocyte cells in the outer layer of the skin. It’s the second most common type of skin cancer in the UK. Most people treated for SCC are completely cured with simple treatment. Usually, squamous cell carcinomas are slow-growing and only spread to other parts of the body if they are left untreated for a long time. Occasionally though, they can behave more aggressively and spread at a relatively early stage.
This is a less common type of skin cancer. Melanoma behaves differently to basal cell and squamous cell cancers. It can grow quickly and needs to be treated early. This section does not cover malignant melanoma, but we have separate information on malignant melanoma.
Rarer types of non-melanoma skin cancer
There are some other rare types of skin cancer:
- Merkel cell carcinoma
- Kaposi's sarcoma
- cutaneous T-cell lymphomaof the skin
Bowen’s disease is sometimes called squamous cell carcinoma in-situ. It’s caused by the abnormal growth of cells in the outer layer of the skin. These cells don’t spread into the deeper layers of the skin. If left untreated, Bowen’s disease may develop into squamous cell carcinoma.
Causes and risk factors of skin cancer
Ultraviolet (UV) light from the sun is the main environmental cause of most skin cancers.
UV light damages the DNA (genetic material) in our skin cells and can cause skin cancer.
Overexposure to the sun or sunburn in childhood are important risk factors in developing basal cell cancers. It’s likely that skin damage from UV light during childhood doesn’t show up until many years later.
Skin cancer is more common than it used to be. This is because people are living longer so their lifetime sun exposure is greater. Sun exposure over a lifetime is more significant in developing squamous cell cancers.
People who work outdoors for a living, such as farm workers, builders and gardeners, are at an increased risk of developing skin cancer because they are often exposed to the sun for long periods of time. This is relevant for both squamous cell and basal cell cancers.
A fair-skinned person who tends to go red or freckle in the sun will be most at risk. Children and young adults who have been overexposed to the sun have an increased risk of developing some form of skin cancer, especially if they have fair skin. This will not show up until later on in life – usually after the age of 40, and often not until the age of 60 or 70. Black- or brown-skinned people have an extremely low risk of developing skin cancer because the pigment melanin in their skin gives them protection.
Regularly using sunlamps and sunbeds can increase the risk of developing some skin cancers. The more you use a sunbed or sunlamp, and the earlier in life you begin using them, the greater your risk.
Previous skin cancer
If you’ve had a skin cancer before, you’re at risk of getting another one. This could be either in the same place as before (a local recurrence) or somewhere else on your body.
Previous radiotherapy treatment
Previous radiotherapy treatment for other conditions can sometimes cause skin cancer (particularly basal cell carcinoma) in the treatment area, later in life.
People who take drugs that lower their immunity (immunosuppressants) – for example, after a kidney transplant – are at an increased risk of skin cancer. Squamous cell cancers are the most common, but basal cell cancers and melanomas are also more common in these people than in the general population. However, the reason for taking these drugs outweighs the potential risk of developing skin cancer.
If you’ve had a transplant, it’s important that you see your doctor regularly to check for early signs of skin cancer.
Exposure to chemicals
Another rare possible cause for non-melanoma skin cancer is overexposure to certain chemicals at work. These include:
- coal tar
- cutting oils
- paraffin waxes
- petroleum derivatives
You should wear protective clothing if you handle these substances at lot. Very small amounts of these chemicals used in the home are unlikely to cause skin cancer, but you should always follow the manufacturer’s instructions when using them.
Most skin cancers are not caused by an inherited faulty gene that can be passed on to other family members. However, families are likely to have the same skin type, which may increase their risk of developing a skin cancer.
People with certain rare hereditary conditions, such as Gorlin syndrome or xeroderma pigmentosum (XP), have a higher risk of developing skin cancer.