Melanoma risks and causes
This page is about the risks and causes of melanoma skin cancer. There is information below about
- A quick guide to what's on this page
- How common melanomas are
- Ultraviolet light
- Moles and melanoma
- Birthmarks and melanoma risk
- Skin colour and freckling
- Where you were born
- Sun exposure now and then
Melanoma risks and causes
There is one main factor that increases the risk of developing melanoma – ultraviolet light. Ultraviolet light comes from the sun or sunbeds. But some people are more at risk of getting melanoma than others. Other risk factors include
- Moles – the more moles you have, the higher your risk
- Being very fair skinned – especially with fair or red hair, or having lots of freckles (although people with darker skins can still get melanoma)
- Sunburn – getting badly sunburned, particularly in childhood, increases your risk of melanoma
- Where you were born – fair skinned people born in a hot country, such as Australia or Israel, have a higher risk of melanoma throughout their life
- Sun exposure – on holiday, as well as sitting in the sun or sunbathing at home
- Sunbeds – using sunbeds, particularly before the age of 35
- Sunscreen – using sunscreens may protect you, as long as you don't spend too long in the sun
- A particular type of birthmark called a large congenital melanocytic naevus (bigger than 20cm across)
There are a couple of other known risk factors. You are more at risk of developing melanoma if a close relative has had it. Having had a melanoma or another type of skin cancer increases your risk. Having a lowered immunity also increases your risk.
You can view and print the quick guides for all the pages in the About melanoma section
About 13,300 people are diagnosed with melanoma in the UK each year. It is the 5th most common cancer overall in the UK, excluding non melanoma skin cancer. Skin cancer rates are more than 5 times higher than they were in the mid 1970’s in Great Britain. Above the age of 20 to 24, the incidence steadily rises with age. It is now the second most common cancer in people under the age of 50. The highest incidence is in people over 85.
Some of the increase in melanoma may be because doctors are better at watching people for signs of melanoma, and detecting it at an early stage. But doctors think that it is to do with a change in how much time we spend in the sun, such as more people taking holidays abroad.
There is one main environmental factor that increases the risk of developing melanoma - ultraviolet light (radiation). Ultraviolet light comes from the sun or sunbeds. But some people are more at risk of getting melanoma than others, as this page explains.
Over exposure to sunlight can cause patches of rough, dry skin called solar keratoses. Some patches are skin coloured, other patches are pink, red or brown. Studies show that people with solar keratoses on their head and neck have a risk of melanoma on their head, neck or limbs that is 4 times higher than the general population.
Some of us have more moles than others. The more moles you have on your body, the higher your risk of melanoma. Of course this doesn't mean you will definitely get melanoma if you have lots of moles. But it does mean you should be very careful about exposing yourself to the sun. And you should keep an eye on all your moles. There is information about this in the page on symptoms of melanoma.
People who have lots of unusually shaped or large moles (atypical mole syndrome) have a higher risk of melanoma than the general population. A large mole is one greater than 5mm in diameter. Also, people with just 1 unusually shaped or very large mole (atypical naevi) have an increased risk of melanoma. The risk increases with the number of atypical naevi, and people with 5 or more have 10 times the risk of people without any atypical naevi.
Birthmarks are coloured marks on the skin and there are many different types. Different types of birthmarks are made up of different types of cells. Most birthmarks, such as the common port wine stains and strawberry marks, carry no risk of developing into a cancer. But a very rare type, called a congenital giant melanocytic naevus, can develop into a melanoma. These marks can also be called large congenital melanocytic naevi. They are made up of cells called melanocytes and look like brown or black moles that are present at birth or develop within the first few months. They are very common on the buttock and these are sometimes called bathing trunk naevi.
People with congenital melanocytic naevi smaller than 20cm don't have a higher risk of developing any type of skin cancer than the general population. But people with a melanocytic naevus larger than 20cm have a higher risk of developing melanoma. Researchers and doctors think that the risk may be between 5 to 10% over the person's lifetime.
About half (50%) of the melanomas that develop in large congenital birthmarks do so by the age of 3 to 5 years. Doctors recommend that you check all birthmarks regularly for any signs of change. But they recommend that large congenital birthmarks are completely removed at an early age if possible. If it is not possible to remove the birthmark, it needs to be checked regularly. UK guidelines recommend that people who have large congenital melanocytic naevi should have their whole skin checked every year by a skin specialist (dermatologist).
People who are very fair skinned, especially with fair or red hair, are more at risk of developing melanoma. So are people with a lot of freckles. People with darker skins can still get melanoma but they have more natural protection against it. It is rare for black people in the UK to get melanoma. If melanoma occurs in African or Asian people they are mostly a type that occurs on the soles of the feet or the palms of the hands (acral lentiginous melanoma). This type of melanoma can also grow under the nail.
In the UK, if you are fair skinned and have a tendency to freckle in the sun, you are most at risk. If you have a tendency to get sunburn, you are at more than average risk of melanoma. People most at risk are those who don't tan at all, such as the fairest skinned people and people who go red and then peel before getting a tan.
Research has looked into the link between sunburn and melanoma. Sunburn definitely increases the risk of melanoma. People who have had sunburn are twice as likely to get melanoma than those who have not. The risk is higher if you have had sunburn several times in your life. This increase in risk is seen with sunburn at all ages, not just in childhood.
Fair skinned people born in a hot country, for example Australia, have an increased risk of melanoma throughout their life. Their risk is higher than people who went to live in a hot country as a teenager or people with similar skin colouring who live in cooler climates. Fair skinned people born in a hot country may have exposure to the sun as a baby and young child when the skin is most delicate. This doesn't mean you will definitely get melanoma, of course. It just means you should be aware of taking care of your skin in the sun.
In the UK, most of us are not exposed to the sun for the whole year. But over the past couple of decades, more and more of us have been going abroad for two or three weeks a year for a holiday and to get a sun tan. The number of people getting melanoma has increased considerably in the UK since it became popular to have a tan and go abroad for holidays.
People who are exposed to strong sunlight now and then, like holidaying in a hot country, are more at risk of melanoma than people who are continuously exposed to sunlight, like people who work outdoors.
People with higher socioeconomic status have a higher risk of melanoma and this is probably due to well off people taking more foreign holidays. But there may be other factors involved. It is also important to be careful during hot spells in the UK.
Sunbed companies will keep trying to tell you that their type of sunbed is safe. But they aren't. And newer machines are no safer than than the old machines. We know from research that the type of ultraviolet light used in sunbeds (UVA) can cause all types of skin cancer. Sunbeds definitely increase your risk of melanoma. In 2012, an analysis of 27 studies reported that people have an increase in risk if they have ever used a sunbed. And the risk was highest for people who had used a sunbed before the age of 35.
Using a sunbed to get a tan before you go on holiday can also increase the risk of melanoma. There is no such thing as a safe tan. For more information, see our section on preventing melanoma.
It is difficult to study how sunscreen affects the risk of melanoma. This is partly because people who use sunscreen may stay longer in the sun because they think they are protected. So they actually get more exposure to ultraviolet light overall. We need more research to understand more about how sunscreen affects melanoma risk.
Sunscreens are now also more effective than those used 10 to 20 years ago. So you may protect against the risk of melanoma in the future by
- using sunscreens with at least SPF 15 (the higher the better) and a good UVA protection
- avoiding the sun when it is hottest (between 11am and 3pm) by spending time in the shade
- covering up (like wearing a T-shirt, wide brimmed hat and sunglasses)
It is very important not to think that using sunscreen allows you to spend longer in the sun. You still have to be careful. Most people don't put enough sunscreen on. There is detailed information about using sunscreen in the section about preventing melanoma.
If you have a close relative who has had melanoma, you are more at risk yourself. This is probably partly because we tend to share the same sort of colouring and skin type as our close relatives. Even if you have darker skin colouring, you should be careful in the sun, as you still have a slight increase in the risk of developing melanoma.
Some families tend to have large numbers of moles, or moles that are unusual (doctors call them atypical moles). The atypical moles tend to be an irregular shape or colour and may be larger than usual. They also have a tendency to become cancerous (malignant). But most atypical moles do not turn into cancer. People with moles like this have a higher than average risk of melanoma.
Researchers have found that the family cancer syndrome - familial atypical multiple mole melanoma syndrome (FAMMM) increases your risk of developing melanoma. People who have FAMMM have more than 50 moles and at least one close relative has been diagnosed with a melanoma. A close relative is a parent, brother, sister, child, aunt, uncle or grandparent. Some families with FAMMM are also at a higher risk of developing pancreatic cancer.
Scientists think that around 1 in 10 cases of melanoma (10%) may be linked to inherited faulty genes. A gene called CDKN2A is known to cause FAMMM. You can read more about this in our section about inherited genes. Cancer Research UK researchers are working on finding out more about this gene, and others. For the small number of families who carry these genes, sun protection is even more important.
People who have had a melanoma have a risk of getting a second melanoma. Their risk is between 8 to 15 times higher than other people in the population. People who have had melanoma and have a parent who has had melanoma have a risk of getting another melanoma that is 30 times higher than the general population.
Studies have also shown that people who have had a non melanoma skin cancer have about 3 times the risk of melanoma of the general population. People who have melanoma of the eye (ocular melanoma), which is very rare, have double the usual risk of developing a skin melanoma.
Research has looked at the link between a type of eczema called atopic dermatitis and melanoma risk. One study found that people with atopic dermatitis had an increased risk of melanoma. But other research suggests that people with this type of eczema have a lower risk of melanoma. So doctors are not clear about this. People who have asthma though have a slightly lower risk.
Studies have shown an increased risk of melanoma for people with Parkinson's disease. More research is needed to understand why this is.
Melanoma risk is also slightly higher in people who have had various other cancers. These include breast cancer, non Hodgkin lymphoma, renal cell carcinoma, certain childhood cancers, prostate cancer, thyroid cancer and leukaemia. The increase in risk may be because the cancer types share genetic or environmental risk factors.
In 2013, researchers carried out a meta-analysis looking at inflammatory bowel disease (crohns disease and ulcerative colitis) and melanoma risk. This means they combined the information from all of the studies and looked at the results together. They found that people with inflammatory bowel disease have an increased risk of melanoma. Treatment for these bowel conditions may include immunosuppressant drugs which we know can increase the risk of some cancers. But there was an increase in melanoma risk even when people had not taken these drugs.
Because more women than men get melanoma, researchers have been very interested in whether hormones had a part to play. There has been a lot of research into this area, looking at
- The role of female sex hormones
- The pill and hormone replacement therapy (HRT)
- Pregnancy factors
There is no conclusive evidence that risk of melanoma is affected by any of these factors. Some women have a natural darkening of the skin during pregnancy. This may make moles show up more clearly. But it is not true that moles are more likely to become cancerous during pregnancy. There is also no evidence that pregnant women diagnosed with melanoma do worse than non pregnant women. If you are worried about this, talk to your GP.
Studies have shown that people with reduced immunity are more likely to develop melanoma. People may have reduced immunity due to infection with HIV or AIDS or medicines given to suppress the immune system after an organ transplant.
Some studies show an increased risk of melanoma in men who have a higher body mass index, although the same has not been shown for women. But any study looking at the risk factors for melanoma needs to take into account how much time the people have spent in the sun. It may be that women with a larger body mass index have less sun exposure than women with a lower body mass index. So this could be why their risk is lower.
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