Lung cancer

Tuesday 1 November, 2016

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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 are part of the respiratory system. As well as the lungs, the respiratory system includes the nose, mouth, windpipe (trachea), and airways (tubes) to each lung. These consist of 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. A number of structures lie in this space, 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 – bean-shaped structures 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. The inner layer (the visceral layer) is attached to the lungs, and the 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 amount of fluid. This fluid allows the two layers of pleura to slide over each other so the lungs move smoothly against the chest wall when you breathe.

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.

The respiratory system

What is lung cancer?

Lung cancer is a malignant tumour that grows 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.

Sometimes a cancer starts in another part of the body and spreads to the lungs. This is known as secondary or metastatic cancer in the lung.

This information is about primary lung cancer only.

What are the different types?

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

Non-small cell lung cancer (NSCLC)

Makes up over 80% of lung cancers. NSCLC may be classified as:

  • adenocarcinoma (begins in mucus-producing cells and is more often found in the outer part of the lungs)
  • squamous cell carcinoma (most commonly develops in the larger airways)
  • large cell undifferentiated carcinoma (the cancer cells are not clearly squamous or adenocarcinoma).
Small cell lung cancer (SCLC)

Makes up about 15–20% of lung cancers. SCLC tends to start in the middle of the lungs, and usually spreads more quickly than NSCLC.

Other tumours starting in the space between the lungs (mediastinum) or chest wall

Thymus gland tumours, germ cell tumours, tumours of nerve tissue and lymph gland tumours (lymphoma) can arise in the mediastinum. These are not strictly lung cancer. Primary tumours of bone, cartilage or muscle can also arise in the chest wall but these are rare.

Mesothelioma

A type of cancer that affects the covering of the lung (the pleura). It is different to lung cancer. There are two main types of mesothelioma: pleural and peritoneal. In most cases, exposure to asbestos is the only known cause of pleural mesothelioma.

For more information see mesothelioma or call Cancer Council 13 11 20 for more information.

How common is lung cancer?

Each year, about 11,000 Australians are diagnosed with lung cancer.1 The average age at diagnosis is 71. It is the fifth most common cancer in Australia and accounts for close to 9% of all cancers diagnosed.

More men than women develop lung cancer.2 The risk of being diagnosed before the age of 85 is 1 in 13 for men and 1 in 22 for women.

What are the risk factors?

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

Tobacco smoking

Smoking causes almost 9 out of 10 lung cancers. Compared with nonsmokers, smokers are 25 times more likely to develop lung cancer.3 In Australia, about 84% of lung cancer cases in males, and 74% in females, are estimated to be a result of tobacco smoking.4

The risk of developing lung cancer is strongly linked to the age a person starts smoking, how long they smoke and the number of cigarettes they smoke.

Second-hand smoking

Breathing in other people’s tobacco smoke (passive or second-hand smoke) can cause lung cancer.

People who have never smoked but who have been frequently exposed to second-hand smoke are 20–30% more likely to develop lung cancer than nonsmokers who have not been exposed. People who have never smoked and have not been around second-hand smoke have about a 0.5% risk of developing lung cancer.

Exposure to asbestos 

People who are exposed to asbestos have a greater risk of developing cancer, particularly pleural mesothelioma (see above).

Although the use of asbestos in building materials has been banned nationally since 2003, it may still be in some older buildings. People who have been exposed to asbestos and are, or have been, a smoker are at even greater risk.

It can take many years after being exposed to asbestos for mesothelioma to develop. This is called the latency period or latent interval, and it is usually between 20 and 60 years.

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 particulate matter, also increases the risk of lung cancer.

Family history

Having a family member diagnosed with lung cancer increases the risk.

Personal history

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

Older age

Lung cancer is most commonly diagnosed in people aged 60 years and older, though it can occur in younger people.

If you are concerned about any of these risk factors, talk to your doctor.

What are the symptoms?

The main symptoms of lung cancer are:

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

A person may have also experienced symptoms such as fatigue, weight loss, hoarse voice, wheezing, difficulty swallowing, and abdominal or joint pain. Lung cancer symptoms can be vague and the disease is often discovered when it is advanced (has 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. However, if you have symptoms, see your doctor without delay.

Sometimes, there are no symptoms and the cancer is found 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: Dr Dishan Herath, Medical Oncologist, Royal Melbourne Hospital, VIC; Sue Lilley, 13 11 20 Consultant, Cancer Council SA; Nev Middleton, Consumer; A/Prof Matthew Peters, Professor of Respiratory Medicine, Faculty of Medicine and Health Sciences, Macquarie University, and Senior Staff Specialist, Department of Respiratory Medicine, Concord Hospital, NSW; Dr Shawgi Sukumaran, Medical Oncologist, Flinders Medical Centre, SA; and A/Prof Shalini Vinod, Radiation Oncologist, Liverpool Hospital, NSW.
1. Australian Institute of Health and Welfare (AIHW), Australian Cancer Incidence and Mortality (ACIM) books: Lung cancer, AIHW, Canberra, 2016.
2. Australian Institute of Health and Welfare (AIHW), Cancer in Australia: an overview 2014, AIHW, Canberra, 2014.
3. Let’s make the next generation tobacco-free: your guide to the 50th Anniversary Surgeon General’s Report on Smoking and Health, Centers for Disease Control and Prevention, Atlanta, 2014.
4. N Pandeya, et al., ‘Cancers in Australia in 2010 attributable to tobacco smoke’, Australian and New Zealand Journal of Public Health, vol. 39, 2015, pp. 464–70.
Updated: 01 Nov, 2016