About lung cancer
Lung cancer begins when abnormal cells grow and multiply in an uncontrolled way in the lungs. Cancer that starts in the lungs is known as primary lung cancer. It can spread to 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 are two large, spongy organs. 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, bean-shaped 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 pleura) lines the lung surface and the outer layer (the parietal pleura) lines the chest wall and diaphragm. The layers are separated by a film of fluid that lets them slide over each other.
This fluid 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 are surrounded by small blood vessels (capillaries).
Inhaled oxygen passes through the alveoli into the blood, while the waste gas (carbon dioxide) moves from the blood into the alveoli. When you breathe out (exhale), carbon dioxide is removed from the body and released back into the air.
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 men and 65% in women are estimated to be a result of smoking tobacco. 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 1 in 5 people (21%) 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 nonsmoker’s risk by up to 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), such as uranium miners, have an increased risk of lung cancer. Air pollution is another risk factor. Contact with the processing of arsenic, cadmium, steel and nickel, and exposure to diesel in the workplace may also be risk factors.
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 human immunodeficiency virus (HIV) may increase the risk of lung tumours.
Lung cancer is most commonly diagnosed in people over the age of 60 years, although it can occur in younger people.
Each year, about 12,200 Australians are diagnosed with lung cancer. The average age at diagnosis is 72. It is the fifth most common cancer in Australia, accounting for 9% of all cancers diagnosed. More men than women develop lung cancer.
A/Prof Nick Pavlakis, President, Australasian Lung Cancer Trials Group, President, Clinical Oncology Society of Australia, and Senior Staff Specialist, Department of Medical Oncology, Royal North Shore Hospital, NSW; Dr Naveed Alam, Thoracic Surgeon, St Vincent’s Private Hospital Melbourne, VIC; Prof Kwun Fong, Thoracic and Sleep Physician and Director, UQ Thoracic Research Centre, The Prince Charles Hospital, and Professor of Medicine, The University of Queensland, QLD; Renae Grundy, Clinical Nurse Consultant – Lung, Royal Hobart Hospital, TAS; A/Prof Brian Le, Director, Palliative Care, Victorian Comprehensive Cancer Centre – Peter MacCallum Cancer Centre and The Royal Melbourne Hospital, and The University Of Melbourne, VIC; A/Prof Margot Lehman, Senior Radiation Oncologist and Director, Radiation Oncology, Princess Alexandra Hospital, QLD; Susana Lloyd, Consumer; Caitriona Nienaber, 13 11 20 Consultant, Cancer Council WA; Nicole Parkinson, Lung Cancer Support Nurse, Lung Foundation Australia.
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