lung cancer
The lungs
The lungs are part of the body system we use to breathe. This is called the respiratory system. It is made up of the
The windpipe divides into two airways. These are called the right main bronchus and left main bronchus. One goes to each lung.
Within the lungs, the left and right bronchus divide into smaller tubes called the secondary bronchi. There are two of these on the left side and three on the right. The lungs are slightly different on each side.
The right lung is divided into 3 sections called the upper, middle and lower lobes. The left lung is divided into 2 sections called the upper and lower lobes.
Each secondary bronchus divides into smaller tubes called bronchioles. They are supported by the surrounding lung tissue.
- Nose and mouth
- Windpipe (trachea)
- Airways to each lung (the right main bronchus and left main bronchus)
- The lungs
The windpipe divides into two airways. These are called the right main bronchus and left main bronchus. One goes to each lung.
Within the lungs, the left and right bronchus divide into smaller tubes called the secondary bronchi. There are two of these on the left side and three on the right. The lungs are slightly different on each side.
The right lung is divided into 3 sections called the upper, middle and lower lobes. The left lung is divided into 2 sections called the upper and lower lobes.
Each secondary bronchus divides into smaller tubes called bronchioles. They are supported by the surrounding lung tissue.
The pleura are 2 fibrous sheets of tissue that cover the lungs
and help to protect them. Doctors usually call these the lining of the
lungs, although this can be a bit confusing as they are on the outside.
The pleura are also called the pleural membranes.
The gap between the pleura is called the pleural space. The pleura produce a lubricating fluid that moistens the gap between them. This helps the pleural membranes to move smoothly over each other when the lungs get bigger and smaller as we breathe.
Lung cancer can spread to the pleura. The cancer cells irritate the pleural membranes and they then make too much fluid.
The fluid collects and reduces the space available for the lung. So your lung can't expand as much as it should and this can make you feel breathless. Build up of fluid between the pleura is called a pleural effusion.
The gap between the pleura is called the pleural space. The pleura produce a lubricating fluid that moistens the gap between them. This helps the pleural membranes to move smoothly over each other when the lungs get bigger and smaller as we breathe.
Lung cancer can spread to the pleura. The cancer cells irritate the pleural membranes and they then make too much fluid.
The fluid collects and reduces the space available for the lung. So your lung can't expand as much as it should and this can make you feel breathless. Build up of fluid between the pleura is called a pleural effusion.
The lungs bring oxygen into our bodies and pass it into the
bloodstream so that it can circulate to every body cell. We use the
muscles of our chest and a large flat muscle under the lungs (the
diaphragm – pronounced di-a-fram) to draw air into the lungs. The
diaphragm is at the base of the chest cavity, just above the stomach.
The chest cavity is sealed so that when you breathe in and the muscles
make it bigger, this creates a vacuum inside, which draws air in through
your nose and down into the lungs.
At the end of the smallest airways in the lungs (the secondary bronchii) are the smallest tubes, the bronchioles. These carry air throughout the lungs. At the end of the bronchioles are air sacs called alveoli. There are millions of these tiny sacs. This is where oxygen is absorbed into the bloodstream from the air that we breathe in. Once in the blood, the oxygen can travel throughout the body and reach every body cell.
As oxygen is being absorbed, carbon dioxide passes back into the alveoli from the bloodstream. This waste gas is removed from the body as we breathe out.
At the end of the smallest airways in the lungs (the secondary bronchii) are the smallest tubes, the bronchioles. These carry air throughout the lungs. At the end of the bronchioles are air sacs called alveoli. There are millions of these tiny sacs. This is where oxygen is absorbed into the bloodstream from the air that we breathe in. Once in the blood, the oxygen can travel throughout the body and reach every body cell.
As oxygen is being absorbed, carbon dioxide passes back into the alveoli from the bloodstream. This waste gas is removed from the body as we breathe out.
Lymph fluid circulates through body tissues and so the lymphatic system is one of the ways that cancer can spread from one part of the body to another. Cancer cells may be released from a tumour in the lung and then get trapped in nearby lymph nodes. Cancer surgeons and medical cancer specialists (oncologists) check your lymph nodes for cancer cells when you are diagnosed. If there are cancer cells in the lymph nodes, this is a sign that the cancer may have spread to other parts of the body and this could affect your choice of treatment.
Lung cancer risks and causes
How common lung cancer is
Lung cancer is the second most common cancer in the United
Kingdom (excluding non melanoma skin cancer). Around 41,400 people are
diagnosed in the UK each year.
In most people, lung cancer is related to cigarette smoking.
Smoking causes nearly 9 out of 10 cases (86%). A further 3% of cases of
lung cancer are caused by exposure to second hand smoke in non smokers
(passive smoking).
Here are some facts about smoking and lung cancer
Cigarette smoking is the main cause of lung cancer. But pipe and cigar smokers are still much more likely to get lung cancer than non smokers. They are also much more likely to get cancer of the mouth or lip.
In the past, lung cancer has always been more common in men than women. Now, because more women smoke, it is almost as common in women.
However long you have been smoking, it is always worth giving it up. Talk to your GP or practice nurse. They will be able to help and support you while you are giving up.
We have information about organisations that help you give up smoking.
Here are some facts about smoking and lung cancer
- The more you smoke, the more likely you are to get lung cancer but it is the length of time you have been a smoker that is most important
- Starting smoking at a young age greatly increases the risk
- Filtered and low tar cigarettes might not increase your risk quite so much, but most smokers cancel this out by taking more, deeper puffs or smoking more cigarettes
- As soon as you stop smoking your risk of lung cancer starts to go down
- Passive smoking (breathing in other people's cigarette smoke) increases the risk of lung cancer, but it is still much less than if you smoke yourself
Cigarette smoking is the main cause of lung cancer. But pipe and cigar smokers are still much more likely to get lung cancer than non smokers. They are also much more likely to get cancer of the mouth or lip.
In the past, lung cancer has always been more common in men than women. Now, because more women smoke, it is almost as common in women.
However long you have been smoking, it is always worth giving it up. Talk to your GP or practice nurse. They will be able to help and support you while you are giving up.
We have information about organisations that help you give up smoking.
Some other things increase lung cancer risk, but they increase the risk far less than smoking. They are
Radon is the second biggest cause of lung cancer after smoking. The risk from radon increases the risk from smoking. Smokers with high indoor levels of radon have a particularly high risk of getting lung cancer. If you are worried about this, the Health Protection Agency Radiation Protection Division has information on how to check radon levels in your house.
People at the highest risk of lung cancer caused by diesel fumes are miners and professional drivers. Information about other workplace chemicals that have a very small risk of causing lung cancer can be found in the statistics area of our News and Resources section.
Based on a large European study, researchers think that 5 to 7% of lung cancers in non smokers are due to outdoor air pollution. In China and India, the use of coal for cooking and for heating the home, and a high level of smokiness in the home, has been shown to increase lung cancer risk. But levels of smoke in UK homes are generally much lower than in China and India.
Chlamydia pneumoniae is a type of bacteria that can cause chest infections. Some studies have shown that people with antibodies to chlamydia pneumoniae have an increased risk of lung cancer. The risk is greater for people who smoke.
Researchers in Sweden found that lung cancer may occur up to 20 years after treatment for breast cancer. The research showed that the women who went on to develop lung cancer were almost all smokers at the time of their breast cancer treatment. Recent research shows that women who have oestrogen receptor negative breast cancer may be at increased risk of developing lung cancer.
Treatment for other types of cancer has also been linked to a slightly increased risk of lung cancer some years later. People may have an increased risk of lung cancer if they have had treatment for
There is also in increased risk of lung cancer in people who have some auto immune conditions. For example research shows that systemic lupus erythematosus (SLE) may double the risk of lung cancer.
- Exposure to radon gas
- Exposure to certain chemicals
- Air pollution
- Previous lung disease
- A family history of lung cancer
- Past cancer treatment
- Previous smoking related cancers
- Lowered immunity
Exposure to radon gas
Radon gas is a naturally occurring radioactive gas which comes from tiny amounts of uranium present in all rocks and soils. The radon gas can build up in homes and other buildings. The highest levels have been found in south west England, but higher than average levels may be found in many other parts of the UK.Radon is the second biggest cause of lung cancer after smoking. The risk from radon increases the risk from smoking. Smokers with high indoor levels of radon have a particularly high risk of getting lung cancer. If you are worried about this, the Health Protection Agency Radiation Protection Division has information on how to check radon levels in your house.
Exposure to certain chemicals
A number of substances that occur in the workplace may cause lung cancer. In particular, these include asbestos, silica, and diesel exhaust. Exposure to asbestos in the construction industry and shipbuilding is now much lower than in the 1960s. But asbestos is still a cause of lung cancer and the risk is increased amongst smokers. Silica which is used in glass making, may cause a condition known as silicosis. This condition increases the risk of lung cancer.People at the highest risk of lung cancer caused by diesel fumes are miners and professional drivers. Information about other workplace chemicals that have a very small risk of causing lung cancer can be found in the statistics area of our News and Resources section.
Air pollution
Air pollution may cause lung cancer. We know this from studies on people exposed to large amounts of diesel exhaust fumes at work for many years. This type of long term occupational exposure may increase lung cancer risk by up to 47% (that is the average risk of lung cancer, plus half again). One study has shown that people living in areas with high levels of nitrogen oxides (mainly from cars and other vehicles) have their lung cancer risk increased by about a third.Based on a large European study, researchers think that 5 to 7% of lung cancers in non smokers are due to outdoor air pollution. In China and India, the use of coal for cooking and for heating the home, and a high level of smokiness in the home, has been shown to increase lung cancer risk. But levels of smoke in UK homes are generally much lower than in China and India.
Previous lung disease
Having had a disease that caused scarring in the lungs may be a risk factor for a type of lung cancer called adenocarcinoma of the lung. Tuberculosis (TB) can make scar tissue form in the lungs. A recent study in China showed that people who have had TB have double the risk of lung cancer. This risk continues for more than 20 years.Chlamydia pneumoniae is a type of bacteria that can cause chest infections. Some studies have shown that people with antibodies to chlamydia pneumoniae have an increased risk of lung cancer. The risk is greater for people who smoke.
A family history of lung cancer
Researchers are looking into the impact of family history on lung cancer. It is likely that there is at least one faulty lung cancer gene that can be passed down in families (inherited). If you have a first degree relative with lung cancer your risk of lung cancer is increased by 51%. The risk is even greater if a brother or sister has lung cancer. This risk is regardless of whether or not you smoke. But families of smokers will all be exposed to cigarette smoke and so have an increased risk of lung cancer whether they have inherited a faulty gene or not.Past cancer treatment
There is some evidence that particular cancer treatments might increase your risk of lung cancer. A review of lung cancer after treatment for breast cancer shows that ways of giving radiotherapy for breast cancer in the past increased the risk of developing lung cancer. But the most up to date methods of giving radiotherapy to treat breast cancer do not seem to increase the risk of primary lung cancer.Researchers in Sweden found that lung cancer may occur up to 20 years after treatment for breast cancer. The research showed that the women who went on to develop lung cancer were almost all smokers at the time of their breast cancer treatment. Recent research shows that women who have oestrogen receptor negative breast cancer may be at increased risk of developing lung cancer.
Treatment for other types of cancer has also been linked to a slightly increased risk of lung cancer some years later. People may have an increased risk of lung cancer if they have had treatment for
- Hodgkin lymphoma
- Some types of non Hodgkin lymphoma
- Testicular cancer
- A type of cancer of the womb
Previous smoking related cancers
People who have had a head and neck cancer, oesophageal cancer or cervical cancer have an increased risk of lung cancer. This may be explained by the fact that the risk of these cancers is higher in smokers. But it could also be a result of radiotherapy treatment.Lowered immunity
HIV and AIDS lower immunity and so do drugs that people take after organ transplants. An overview of research studies shows that people with HIV or AIDS have a risk of lung cancer that is 3 times higher than people who do not have HIV or AIDS. People who take drugs to suppress their immunity after an organ transplant have double the usual risk of lung cancer.There is also in increased risk of lung cancer in people who have some auto immune conditions. For example research shows that systemic lupus erythematosus (SLE) may double the risk of lung cancer.
Diet
Researchers have recently been looking into links between vitamins and lung cancer. Fresh fruit and vegetables may help to prevent cancer because they contain chemicals that can prevent cell damage. The antioxidant vitamins A, C and E were thought to help reduce the risk of lung cancer, but the evidence for this is not clear. But there is now strong evidence that flavonoids, found in many fruits and vegetables, do help to reduce lung cancer risk. But changing your diet won't reduce your risk of lung cancer much if you carry on smoking. The most important thing by far is to stop smoking.Researchers have looked into whether taking extra vitamin E and beta carotene may help stop smokers getting lung cancer. The body uses beta carotene to make vitamin A. Early results suggest that vitamin supplements do not help to prevent lung cancer. They may even be harmful in smokers or people who have been exposed to asbestos in the past. Another similar substance to beta carotene, called beta cryptoxanthin, is found in fruits such as oranges and mangoes. It may lower lung cancer risk, but we don't know how it affects smokers yet.
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