Skin cancer risks and causes

Remember that this section is about basal cell skin cancer and squamous cell skin cancer. Together these are called non melanoma skin cancer (NMSC). There is a type of skin cancer called melanoma. We have a separate section on melanoma, including a page on melanoma risks and causes.

Almost 100,000 cases of non melanoma skin cancer are diagnosed in the UK each year. This makes it the most common type of cancer by far. This type of cancer tends to be under reported. The actual number of cases could be more.

Because skin cancers are easy to treat and cure, these skin cancers are often left out of national cancer statistics (for example, when we say breast cancer is the most common cancer type in the UK).

Most skin cancers are caused by long term exposure to the sun. Look at the preventing skin cancer page in this section for lots of information about how to protect your skin from the sun.

The ultraviolet light in sunlight damages the DNA in the skin cells. This damage can happen years before a cancer develops. The sun’s rays contain 3 types of ultraviolet light.

• UVA makes up most of our natural sun light and causes skin aging
• UVB is what makes the sun burn the skin and is the main cause of non melanoma skin cancer
• UVC is mostly filtered out by the atmosphere of the earth

There are several factors that affect your risk from sun exposure

• How much time you spend outdoors
• Your natural skin colour
• Your use of sun beds

There are two types of non melanoma skin cancer  ̶̶  basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). A history of sunburn or recreational exposure to sunlight increases the risk of BCC. Risk is especially high if you had several episodes of sunburn in childhood. The risk of SCC is linked to overall sun exposure through your life. This means that outdoor workers such as farm workers, gardeners and building site workers have an increased risk. Sunburn in childhood is also linked to SCC in some studies.

Fair skinned people with light coloured hair and eyes, or those more likely to burn than tan, are more at risk of sun damage than dark skinned people. This is because their skins make less of the protective pigment called melanin. Black skinned people are less likely to get skin cancer, but they can be at risk on the soles of the feet and palms of the hands.

Albinism is an inherited genetic condition in which the skin makes no melanin at all. Albino people have very white skins and pale blonde hair. They are at higher than average risk of skin cancer because their skin has no natural protection against the sun.

It has always been thought that UVB is the main risk for skin cancer. Sunbeds produce mostly UVA but all produce some UVB too. UVA damages the skin and there is increasing evidence that UVA may also cause skin cancer. So sunbeds may increase your risk of non melanoma skin cancer. The evidence is strongest for a link between sunbeds and squamous cell skin cancer.

Basal cell and squamous cell skin cancers develop very slowly. As you get older you have more time to build up sun damage to your skin. So the older you are, the more likely you are to get a non melanoma skin cancer. But skin cancers can develop in younger people too.

If you have had a non melanoma skin cancer, you have a greater risk of getting another of the same type. According to research, the risk is up to 15 times the average risk of skin cancer. If you've had a melanoma, you have 3 to 5 times higher than average risk of getting a non melanoma skin cancer. So cover up in the sun and look out for any signs of another skin cancer.

Most skin cancers do not run in families. But research programmes have found a few families who do seem to have a higher number than normal. If you have a parent who has had squamous cell skin cancer, you have a 2 to 3 times higher than average risk of getting one yourself. Family history is probably also linked to increased risk of basal cell skin cancer.

Of course, skin type runs in families. So people from fair skinned families will be more at risk than dark skinned families. But there may be some inherited genes that increase the risk of skin cancer in some families.

People with certain skin conditions can be more likely to develop skin cancer. These include the following conditions.

Psoriasis is not a risk in itself. But some of the treatments (such as ultraviolet light) may increase your risk. Having had treatments such as psoralen ultraviolet light treatment (PUVA) in the past may increase your risk of getting non melanoma skin cancer. But the UV exposure is carefully monitored in this treatment and it is good for your psoriasis. The benefits and risks will be carefully balanced by your doctor.

Scarring, for instance from burns or skin ulcers, may make your skin more at risk from sun damage. This may increase your risk of non melanoma skin cancer.

Solar keratosis is also called actinic keratosis. This is a skin condition either caused by many years exposure to the sun or by intense sun exposure on fair skin. Small rough red patches of skin develop  ̶̶  often on the face, hands or, if you are bald, the scalp. These are a sign that your skin has already been damaged by the sun and you should take extra care to cover up when you go out. Solar keratosis can be treated with cryosurgery, chemotherapy creams, retinoids or photodynamic therapy.

Xeroderma pigmentosum is a very rare inherited genetic skin condition. It is usually there from birth. But there is another type of this condition called xeroderma pigmentosum variant that does not show up until the teens. If you have this condition, your skin cannot repair damage from the sun. You should avoid all sun exposure and other sources of UV light. Even so, people with this condition often get skin cancers on exposed skin.

Gorlin’s syndrome is also called naevoid basal cell carcinoma syndrome. It is a very rare inherited genetic condition that is there from birth. It causes many basal cell cancers to develop. Very rarely, it can appear in a family with no past history of the condition because of a random gene mutation.

If you have had radiotherapy before, the treatment area will be more at risk from sun damage. You should keep it covered and use high factor sun cream. If you have been exposed to radiation through your job, you will also have a slightly increased risk of non melanoma skin cancer.

Contact with a number of different chemicals can increase your risk of non melanoma skin cancer. These include the following

• Coal tar
• Soot
• Pitch
• Asphalt
• Creosote
• Paraffin wax
• Petroleum products, such as mineral oil or motor oil
• Arsenic

If you have had an organ transplant or a bone marrow transplant and are taking drugs to stop rejection, you have an increased risk of getting a skin cancer in the future. The risk increases the longer you are taking these drugs. This risk is much less important than the illness you originally had treatment for. But it helps to know about it so that you can pick up any symptoms of skin cancer early on, when it is easier to treat. People with HIV or AIDS also have an increased risk of skin cancer. The autoimmune condition sarcoidosis weakens the immune system and people with this condition have an increased risk of squamous cell skin cancer.

This is a common virus that has several different strains. Some of these are associated with other types of cancer, for example, cervical cancer. Bowen's disease is a very early form of skin cancer. Rarely, it can develop in the genital area. Research into this condition has shown that infection with the HPV virus may cause Bowen’s disease in the genital area.

In people with a rare inherited condition called epidermodysplasia verruciformis, HPV plays an important part in the development of skin cancer. There is research looking into whether HPV may be linked to skin cancers in people who have a weakened immune system (see above).

Two studies have shown that cigarette or pipe smokers have double the risk of squamous cell carcinoma compared to non smokers. They showed that the risk increased with the number of cigarettes smoked a day. The researchers felt that the increased risk may be because of the direct effects of tobacco smoke. Or because smokers are more likely to get HPV infection of the skin (see above). However, other studies have not shown a link with smoking. So we need more research to clarify this issue.