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 non melanoma skin cancers are easy to treat and cure, they 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 exposure to the sun. This may be long term exposure, or short periods of intense sun exposure and burning. 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. It goes deeper into the skin and causes skin ageing. It is now also linked to skin cancer
• UVB is most likely to burn the skin and is the main cause of non melanoma skin cancer
• UVC is filtered out by the atmosphere of the earth (ozone layer)

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 (artificial UV radiation)

There are 2 main 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. People with black skin 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 is now also linked to skin cancer. We know the use of sunbeds causes melanoma, and there is now evidence that sunbeds may increase the 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 about 10 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.

If you have had a non melanoma skin cancer before, you may also be at increased risk of developing a second primary cancer (other than skin cancer). It is not clear why this is.

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. People who have a family history of melanoma have an 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.

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. National guidelines recommend transplant patients have yearly check ups with a skin specialist to look for skin cancers and to learn what symptoms to look for. People with HIV or AIDS may also have an increased risk of non melanoma skin cancer.

People with inflammatory diseases such as inflammatory bowel disease or rheumatoid arthritis may have an increased risk of skin cancer. This may be due to the condition itself or the medication you take to suppress your immune system, or both.

This is a common virus that has several different strains. Some of these are associated with other types of cancer, for example, cervical cancer. Some studies have shown that a number of non melanoma skin cancers contain DNA from some types of HPV.

One study has shown that people with genital warts (caused by HPV types 6 and 11) have an increased risk of basal cell skin 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 this area.

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

Contact with a number of different chemicals in certain jobs 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