Causes of cancer

Diet and lifestyle

There are over 200 different types of cancer. We don’t know the causes for each one of these cancers, but we do know about some. It is important to note that for many cancers, there may be more than one cause. One of the biggest risks is increasing age. Cancer can occur at any age but the risk of developing it increases with age; over 70% of people who get cancer are over the age of 60.

We make lifestyle choices everyday; some we know increase our risk of developing cancer, others may have an influence on our risk.  For example, smoking is a major cause of lung cancer and is a factor in other cancers, such as bladder cancer and cancers of the mouth and throat.

Other factors are heavy alcohol consumption and exposure to sunlight.

In this section, there are a number of questions and answers about diet and lifestyle as causes of cancer. You may also find it helpful to look in our section about diet and the cancer patient, for further information on healthy diets.

Enviromental & occupational

A carcinogen is something that causes cancer. Contact with certain harmful substances in the workplace can cause cancer.

We know, for example, that 9 out of 10 people who develop mesothelioma (a rare type of cancer affecting the linings of the lung and abdomen) have had contact with asbestos. People who have worked in industries such as ship- building and construction may have come into contact with asbestos. Its use is now banned in this country.  For further information about this type of cancer look in our Mesothelioma information centre.

Another example is exposure to certain chemicals in the workplace; those used in dye factories, rubber, gas works and other chemical industries have all been linked to bladder cancer. These chemicals have now been banned. See our bladder cancer information centre for further information about this type of cancer.

Environmental causes include natural radiation, for example, from the sun. We know that most skin cancers are caused because of prolonged exposure to the sun.

It is important to remember that we don’t know the cause of many cancers and that there is often more than one cause. Also, although cancer can occur at any age, one of the biggest risks of it developing is increasing age.

In this section, there are a number of questions and answers about environmental and occupational causes of cancer.

Cancer genetics – how cancer sometimes runs in families

This section is for anybody who is worried that cancer might run in his or her family. It is also for people who have been advised, or who have decided, to see a cancer genetics specialist or genetic counsellor. If you don’t have at least two relatives with the same type of cancer on the same side of your family, the information in this section is probably not relevant to you.

Many people ask themselves why cancer has happened to them or to a close relative. People often feel that cancer is such an awful disease that they want to know why they developed it. They might think about their own medical history or about risks in the environment. People sometimes also think that several cases of cancer in their family might be connected, and that they have inherited an increased cancer risk. However, only a small minority (5-10%, or less than 10 out of 100 cases) of cancers are clearly linked to an inherited gene change. Unfortunately, most cancers happen for reasons we don’t fully understand.

Cancer is a common disease. It is estimated that in the UK about 1 in 3 people will get cancer during their lives. Most people who get cancer are over 65. It is relatively rare for young people (people under 50) to get cancer. If you have only one elderly relative with cancer, you are not at a significantly increased risk of getting the same cancer yourself.

This section outlines our current understanding of how specific genes are sometimes involved in the development of some cancers. It describes how cancer genetic services (also called familial cancer services) are provided by the NHS. It explains some of the science and the practice of genetic testing and addresses the questions you might have about genetic tests.

Not all parts of this information will be equally relevant to everyone. The menu on the left hand side can help you find the information that is useful for you. Some key information is repeated in several sections to ensure that anyone dipping into the section sees the information in context.

If you think this section has helped you, do pass it on to any of your family and friends who might want to have this information.


It is important to remember cancers are not infectious and cannot be caught from someone. However, there are a number of different viruses that are thought to be contributing factors in the development of cancer.

For example, exposure to HPV (human papilloma virus) is known to increase a woman’s risk of developing cancer of the cervix. For further information about this, see CancerBACUP’s section about HPV.

Other viruses include the Epstein-Barr virus, which is linked to some types of lymphoma.

There is also a bacterial infection known as H-pylori which is linked to a rare type of stomach cancer.

See Q&As on this topic for a number of questions and answers about viruses and cancer.

Like all warts, cervical warts are caused by a virus, the human papilloma virus (HPV). There are over 100 types of HPV, some types cause common skin warts, and others genital warts. There are about 30 types which can infect the cervix. If the cervix is infected with the virus this may cause visible warts but in many women infection can be only detected microscopically by a smear test.

Genital HPV is usually spread though direct sexual contact, including oral sex, but non-sexual infection, although rare, is also possible. The virus can also lie dormant in the body for many years. It would be wise not to assume anything about how you contracted the wart until you have had a full discussion with your husband about this. When transmission has occurred from an infected person, warts can take anything from a few weeks up to several months to appear. Generally the types of HPV that infect the skin of the hands and body don’t infect the genital area, so it would be very unusual to contract cervical warts in this way.
About half of the different types of HPV that can infect the cervix are associated with cervical cancer. The presence of the HPV infection in the cervix does increase the risk that mild abnormalities in the cervical tissue will progress to severe abnormalities and very occasionally to cervical cancer. However the overwhelming majority of HPV infections of the cervix never lead to cancer. Most HPV infections seem to go away by themselves, or with simple treatment from a specialist, without causing any cervical abnormalities. Cervical cancer can almost always be prevented by regular follow-up with cervical smears to detect and treat pre-cancerous changes before they go on to become invasive cervical cancer.

The most important thing to do now is to discuss the treatment and follow-up of the cervical wart with your specialist.

I have a cervical wart. My husband and I have been married 15 years. Does this mean he has been having an affair? Can this be passed on by oral sex? Will I get cancer? What do I do?

The short answer to your question is no, there is no link between sickle cell anaemia and cancer of any type.

Although sickle cell anaemia and cancer can both be serious illnesses, there is no link between the two conditions.  Sickle cell anaemia never turns into cancer, and people with sickle cell disease are not at any greater risk than other people of developing cancer.

Hydroxyurea is a drug sometimes used to treat sickle cell disease.  There are concerns that many years of treatment with hydroxurea can increase the risk of getting a ‘blood’ cancer but the risk is yet to be proven and appears to be small.

Sickle cell disease is due a faulty gene, which is inherited, so it runs in families.  It occurs mainly in people of African-Caribbean descent, and in some parts of central Africa is very common indeed.  It is also, much less commonly, found in people from parts of India, Saudi Arabia, Greece, Italy and North Africa.

If you inherit the sickle cell gene from just one parent then the condition is quite mild and usually causes no problems (this is called sickle cell trait), but if you inherit the gene from both your parents then this is sickle cell disease, which is much more serious.  However, over the last 25 years the treatment of the condition has improved a great deal and the outlook is very much better now than it used to be. 

For further information and support about sickle cell anaemia you may find it helpful to contact The Sickle cell society.

Is there any link between sickle cell anaemia and cancer?

It may help to answer your question by starting with an explanation about lymphomas in general.

Lymphomas are cancers of the lymphoid tissue which is part of our body’s immune system.

Our immune system protects us from infection. It is a complex system made up of the bone marrow, the thymus gland (which lies behind the breast bone), the spleen and the lymph nodes (or lymph glands).

One of the most important cells in our immune system is a type of white blood cell called a lymphocyte. There are two types of lymphocytes: ‘B-cells’ and ‘T-cells’. All lymphocytes are produced in the bone marrow and start life as young, immature cells called stem cells. Some lymphocytes continue their development in the bone marrow or lymph nodes and these are called B-cells but others move to the thymus gland and they are called T-cells.

Many years ago it was thought that lymphomas could be divided into just two conditions: Hodgkin’s disease (named after Thomas Hodgkin, the London doctor who first described it over 100 years ago) and non-Hodgkin’s lymphoma (NHL). With the passage of time it has become clear that NHL is not a single illness but includes a number of cancers, which behave very differently.

The description and classification of the various types of NHL has developed over the years as more has been learnt both about the immune system and the cancers themselves. The most recent classification still recognises the difference between Hodgkin’s disease and NHL but then goes on to divide NHL into some fifteen different tumour types.

The cause for the great majority of these different types of NHL remains a mystery but in three types of the disease, all of which are very rare in the UK, a link with viruses has been established. These are Burkitt’s lymphoma, Burkitt-like lymphoma and post-transplant lymphom

In 1956 a British surgeon called Dennis Burkitt was working in equatorial AfricH described an unusual type of lymphoma which was very common in children in that region. This became known as Burkitt’s lymphomLater research showed that B-lymphocytes in these children became infected with a virus, the Epstein-Barr virus, or E-B virus. Epstein-Barr virus infections are common and usually cause no problems but in central Africa many of the children had chronic malaria infections which reduced their resistance to the virus. In some cases this allowed the virus to change the infected B-lymphocytes into cancerous cells leading to the development of the lymphom

In recent years it has been recognised that in the western world there is one type of NHL where the tumour cells have very similar appearances under the microscope to those of Burkitt’s lymphoma. This rare condition has been called Burkitt’s-like lymphoma. Further research has shown that a high proportion of patients with Burkitt-like lymphoma (but not all) are HIV positive and many have AIDS. It seems that in this condition once again an Epstein-Barr virus infection occurs and because the HIV has reduced the patient’s immunity the Epstein-Barr virus is able to survive and ‘transform’ the normal B-lymphocytes to cancerous cells.

The same situation has been seen in some patients who have had organ transplants. Often after organ transplantation drugs are given for some time, often years, to suppress the patient’s immunity in order to reduce the risk of rejection of the grafted organ. Some of these patients appear to develop E-B virus infections and once again, as their resistance is reduced, this may lead to the development of a B-cell lymphom

All three of these virally-related types of NHL behave in a very aggressive way and need immediate treatment.

In the African children with Burkitt’s lymphoma chemotherapy gives a high cure rate but the Burkitt-like lymphoma and post-transplant lymphomas tend to be more resistant to treatment. Although a variety of different drug combinations have been used cure is not possible in the majority of people. This means that a number of clinical trials are in progress to try and improve the results of treatment.

In conclusion, the likelihood of your husband’s NHL being one of those types with a known viral cause is very, very remote. Almost certainly he has one of the forms of lymphoma for which no definite cause is known.

My husband has recently been diagnosed as having a lymphoma. We read about someone who has a Burkitt’s like lymphoma and the article said it was due to a virus. Is my husbands lymphoma also due to a virus?

Wart virus (also known as human papillomavirus or HPV) is known to be associated with abnormalities in the cervix known as CIN which if untreated can sometimes develop into cancer of the cervix. It is much less commonly associated with similar changes in the cells of the vagina known as VAIN (vaginal intraepithelial neoplasia) but this only very rarely leads to vaginal cancer. So once the cervix has been surgically removed (as it will have been if you have had cervical cancer), then there is no risk of getting a new cervical cancer and the chances of getting vaginal cancer are very slim indeed. There is always a very small risk of a recurrence of the original cervical cancer, but there is absolutely no evidence that having the wart virus in the vagina will increase this risk.

Although wart virus is known to be one of the factors in the development of most cervical cancers, it is also found in many other women who will never develop cervical cancer. So having the wart virus certainly does not mean a woman will develop cervical cancer. In fact only a very small number of women who ever have a wart virus will develop cancer or even pre-cancerous areas on the cervix.

There are over 80 different types of the wart virus, and some of these types are more likely to be associated with cancer development than others. For example some types are commonly found in women with cervical cancers, whereas other types just cause common skin warts. There are also other factors that may contribute to the risk of cancer; these include number of sexual partners, age, heavy smoking, number of children and other genital infections.

At this stage there is no known method for getting rid of the virus. It is likely to just go way on its own accord with the help of your natural body’s defences. It is certainly important, however, that you continue to have regular smears and examinations as follow up after your cancer.

I had a hysterectomy for cervical cancer two years ago. My doctor has taken a smear from my vagina and says I have a wart virus. Does it mean I will develop another cancer? Is there anything I can do to get rid of this?

Cancer of the vulva is a rare cancer. It usually affects women between the ages of 55 and 75, but can occur in younger or older women.

The cause of most vulval cancers remains unknown but there are a number of conditions that can affect the vulva which will sometimes lead to cancer after many years. These are: n VIN (vulval intraepithelial neoplasia) which can occur in the skin of the vulva and is linked to infection by some types of wart virus, known as human papilloma virus (HPV). There are three levels of abnormality: VIN1, VIN2 and VIN3. VIN3 is the most abnormal and, in some women, can develop into cancer of the vulva if left untreated. n vulval lichen sclerosus and vulval lichen planus. These are two non-cancerous conditions which cause inflammation of the skin of the vulva and occasionally can lead to the development of a cancer after a number of years.

Also there is evidence that cigarette smoking may increase the risk of developing both VIN and vulval cancer. This may be because smoking depresses the immune system.

My mother has been told she might have a cancer of her vulva. What might have caused this?

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Causes of cancer

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