Lung cancer

Monday 1 December, 2014

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On this page: The lungs | What is lung cancer? | What are the different types? | How common is lung cancer? | What are the risk factors? | What are the symptoms?

The lungs 

The lungs are the main organs for breathing, and make up part of what is called the respiratory system. The respiratory system also includes the nose, mouth, windpipe (trachea) and airways to each lung. The airways to each lung consist of large airways (bronchi) and small airways (bronchioles). 

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). Carbon dioxide is released back into the atmosphere – and removed from the body – as you breathe out (exhale). 

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. 

A number of structures lie in the space between the lungs (the mediastinum, including:

  • the heart and large blood vessels
  • the windpipe (trachea), the tube that carries air into lungs
  • the oesophagus (the tube that carries food from the mouth to the stomach)
  • lymph nodes that collect lymph fluid and foreign matter from the lungs.

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. Its inner layer (the visceral layer) is attached to the lungs and its outer layer (the parietal layer) lines the chest wall and diaphragm. Between the two layers is the pleural cavity (also called pleural space), which normally contains a small volume of fluid. This fluid allows the two layers of pleura to slide against each other so your lungs move smoothly against the chest wall as you breathe.

A diagram of the respiratory system

What is lung cancer?

Lung cancer is a malignant tumour in the tissue of one or both of the lungs.

A primary cancer starts in the lungs, while a secondary or metastatic cancer starts somewhere else in the body and spreads to the lungs.  

What are the different types?

There are several types of lung cancer, which are classified according to the type of cells affected. Cancers are named for the way the cells appear when viewed under a microscope.

Non-small cell lung cancer (NSCLC): Makes up over 60% of lung cancers. NSCLC is classified as:

  • squamous cell carcinoma (it mainly affects the cells that line the tubes into the lungs (bronchi)
  • adenocarcinoma (affecting smaller airways)
  • large cell carcinoma (large round cells under the microscope).

Other less common subtypes also exist.

Small cell lung cancer (SCLC): Makes up about 12% of lung cancers. SCLC tends to start in the middle of the lungs, and it usually spreads more quickly than NSCLC. Types include:

  • small cell carcinoma
  • mixed small cell/large cell carcinoma.
Less common lung cancers

Other less common cancers can form in the thoracic (or chest) area. These are known as thoracic cancers and include thymomas, mediastinal tumours and chest wall tumours.


A rare type of cancer that affects the covering of the lung (the pleura). It is almost always caused by exposure to asbestos. It is very different to lung cancer. We have a separate section on mesothelioma.

How common is lung cancer?

About 11,270 people (59% males, 41% females) were diagnosed with lung cancer in Australia in 2012. It is the fifth most common cancer in Australia and is most commonly diagnosed in people aged 60 years and older.

What are the risk factors?

While the causes of lung cancer are not fully understood, there are a number of risk factors associated with developing the disease. These factors include:


Lung cancer is most commonly diagnosed in people aged 60 years and older.

Family history

Having family members who have been diagnosed with lung cancer increases your risk.

Personal history

The risk of developing lung cancer is increased if you have been previously diagnosed with lung diseases such as lung fibrosis, chronic bronchitis, emphysema, and pulmonary tuberculosis.

Tobacco smoking

About one in 10 smokers develop lung cancer. Studies from a number of countries suggest that a life-long smoker has between a 10 and 20% risk of developing lung cancer. However, compared with non- smokers, smokers are more than 10 times more likely to develop lung cancer. In Australia about 90% of lung cancer cases in males, and 65% in females, are estimated to be a result of tobacco smoking. The risk of lung cancer among smokers is strongly related to the length of time and the number of cigarettes a person has smoked.

Passive smoking

Breathing in someone else’s tobacco smoke (passive or secondhand smoking) can cause lung cancer. Non-smokers who have been frequently exposed to secondhand smoke are 20–30% more likely to develop lung cancer than non-smokers who have not been exposed. People who have never smoked and have not been around secondhand smoke have about a 0.5% risk of developing lung cancer.

Exposure to asbestos 

Although the use of asbestos has been banned nationally since 2003, it may still be in some older buildings. People who are exposed to asbestos have a greater risk of developing cancer. Some people are exposed to asbestos at work or during home renovations. People who have been exposed to asbestos and are, or have been, a smoker are at even greater risk.

Exposure to other elements

Contact with the processing of steel, nickel, chrome and coal gas may be a risk factor. Exposure to radiation and other air pollution, such as diesel fumes, also increases the risk of lung cancer. If you are concerned about your risk factors, talk to your doctor.

If you are a smoker

If you need help quitting, call Quitline on 13 78 48.

Smoking is addictive and this is the main reason people continue to smoke even though many may be concerned about the risks or have tried to quit. Your doctors understand this and will consider it when caring for you. They shouldn’t regard you negatively because you are (or were) a smoker.

What are the symptoms?

The main symptoms of lung cancer are:

  • a new dry cough or change in a chronic cough
  • chest pain or breathlessness
  • repeated bouts of pneumonia or bronchitis
  • coughing or spitting up blood.

A person may have also experienced symptoms such as fatigue, weight loss, hoarseness or wheezing, difficulty swallowing, and abdominal or joint pain. Lung cancer symptoms can be vague and the disease is often discovered when it is advanced (spread to other parts of the body).

Having any one of these symptoms does not necessarily mean that you have cancer. Some of these symptoms may be caused by other conditions or from the side effects of smoking. Talk to your doctor to have your symptoms checked.

Sometimes, there are no symptoms and the cancer is detected during routine tests (often an x-ray or CT scan) for other conditions. If so, the cancer is more likely to be in an early stage of development (confined to the lungs).

"I smoked in the past, but I had quit. I just kept having continual colds and I started coughing up blood." - James

Reviewed: Prof Kwun Fong, Thoracic and Sleep Physician and Director, UQ Thoracic Research Center, The Prince Charles Hospital, QLD; Clare Brown, Case Manager for Thoracic Surgery, Royal Prince Alfred Hospital, NSW; Glenda Colburn, Director, Lung Cancer National Program, The Australian Lung Cancer Foundation; Prof David Ball, Chair, Lung Service, Peter MacCallum Cancer Centre; Dr Arman Hasani, Medical Oncologist, Sir Charles Gairdner Hospital, WA; Dr Paramita Dasgupta, Viertel Cancer Research Centre, Cancer Council QLD; Carmen Heathcote, Registered Nurse, Cancer Council QLD; Frances McKenzie, Cancer Connect volunteer, QLD.
Updated: 01 Dec, 2014