- Lung cancer
Lung cancer begins when abnormal cells grow and multiply in an uncontrolled way in one or both of the lungs. Cancer that starts in the lungs is known as primary lung cancer. It can spread to other parts of the body such as the lymph nodes, brain, adrenal glands, liver and bones.
When cancer starts in another part of the body and spreads to the lungs, it is called secondary or metastatic cancer in the lung.
The information here is about primary lung cancer only.
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The lungs are the main organs for breathing, and are part of the respiratory system. As well as the lungs, the respiratory system includes the nose, mouth, trachea (windpipe), and airways (tubes) to each lung. There are large airways known as bronchi (singular: bronchus) and small airways called bronchioles.
The lungs look like two large, spongy cones. Each lung is made up of sections called lobes – the left lung has two lobes and the right lung has three.
The lungs rest on the diaphragm, which is a wide, thin muscle that helps with breathing.
The space between the two lungs is called the mediastinum. Several structures lie in this space, including:
- the heart and large blood vessels
- the trachea – the tube that carries air into the lungs
- the oesophagus – the tube that carries food to the stomach
- lymph nodes – small structures that collect and destroy bacteria and viruses.
The lungs are covered by two layers of a thin sheet of tissue called the pleura, which is about as thick as plastic cling wrap. The inner layer (the visceral layer) lines the lung surface, and the outer layer (the parietal layer) lines the chest wall and diaphragm. The layers are separated by a film of fluid that lets them slide over each other.
This helps the lungs move smoothly against the chest wall when you breathe. The pleural cavity is the potential space between the two layers, but there is no space between them when the lungs are healthy.
The respiratory system
How breathing works
When you breathe in (inhale), air goes into the nose or mouth, down the trachea and into the bronchi and bronchioles. At the end of the bronchioles, tiny air sacs called alveoli pass oxygen into the blood and collect the waste gas (carbon dioxide).
When you breathe out (exhale), carbon dioxide is removed from the body and released back into the atmosphere.
There are two main types of primary lung cancer. These are classified according to the type of cells affected.
Types of lung cancer
non-small cell lung cancer (NSCLC)
|NSCLC makes up about 85% of lung cancers. It may be classified as:
|small cell lung cancer (SCLC)||SCLC makes up about 15% of lung cancers. It tends to start in the middle of the lungs, and usually spreads more quickly than NSCLC.|
Other types of cancer can also affect the lung area, but are not considered lung cancer. These include tumours that start in the space between the lungs (mediastinum) or in the chest wall.
For more on this, see Pleural mesothelioma.
The causes of lung cancer are not fully understood, and some people develop lung cancer without having any known risk factors. The factors listed below are known to increase the risk of developing the disease. Having these risk factors does not mean you will develop lung cancer, but if you are concerned about your risk, talk to your doctor.
In Australia, about 90% of lung cancer cases in males and 65% in females are estimated to be a result of tobacco smoking. The earlier a person starts smoking, the longer they smoke and the more cigarettes they smoke, the higher the risk of developing lung cancer. However, about one-fifth (21%) of people who are diagnosed with lung cancer have never been smokers.
Breathing in other people’s tobacco smoke (passive or second-hand smoke) can cause lung cancer. Living with a smoker increases a non-smoker’s risk by 20−30%.
Exposure to asbestos
People who are exposed to asbestos are more likely to develop lung cancer or pleural mesothelioma. Although the use of asbestos in building materials has been banned across Australia since 2004, there is still asbestos in some older buildings and fences.
Exposure to other elements
People exposed to radioactive gas (radon) in the workplace, such as uranium miners, have an increased risk of lung cancer. Contact with the processing of arsenic, cadmium, steel and nickel may also be a risk factor.
You may be at a higher risk if a family member has been diagnosed with lung cancer.
Having another lung disease (e.g. lung fibrosis, chronic bronchitis, pulmonary tuberculosis, emphysema) or HIV infection may increase the risk of lung tumours.
Lung cancer is most commonly diagnosed over the age of 60 years, though it can occur in younger people.
Each year, about 11,500 Australians are diagnosed with lung cancer. The average age at diagnosis is 71. It is the fifth most common cancer in Australia and accounts for 9% of all cancers diagnosed. More men than women develop lung cancer. The risk of being diagnosed before the age of 85 is 1 in 13 for men and 1 in 21 for women.
Dr Henry Marshall, Thoracic Physician, The University of Queensland Thoracic Research Centre, The Prince Charles Hospital, QLD; Dr Naveed Alam, Thoracic Surgeon, St Vincent’s Melbourne and Epworth Richmond Hospitals, VIC; A/Prof Martin Borg, Radiation Oncologist, GenesisCare, SA; Dr Lisa Briggs, Consumer; Kirsten Mooney, Thoracic Cancer Nurse Coordinator, WA Cancer & Palliative Care Network, WA; Claire Mulvihill, Lung Cancer Support Nurse, Lung Foundation Australia; Caitriona Nienaber, 13 11 20 Consultant, Cancer Council WA; A/Prof Nick Pavlakis, President, Australasian Lung Cancer Trials Group, President Elect, Clinical Oncology Society of Australia, and Senior Staff Specialist, Department of Medical Oncology, Royal North Shore Hospital, NSW. We also thank the health professionals, consumers and editorial teams who have worked on previous editions of this title.
View the Cancer Council NSW editorial policy.
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