Lung Cancer

What is lung cancer?

Lung cancer refers to the uncontrolled growth of abnormal cells in the tissue of one or both lungs, which takes the form of a malignant tumour.11  The cancer can be found in the airway tubes (bronchus) or in the spongy lung tissue (alveoli). Lung tumours may also be caused by cancer which has spread from another part of the body but these are not considered as lung cancer per se.

There are two main sub-classifications of primary lung cancer:

  • Non-small cell lung cancer (NSCLC) – this is the most common form of lung cancer, making up approximately 85% of all lung cancer cases. NSCLC can be classified into a number of types, including:1
    • Adenocarcinoma – typically found on the outer area of the lungs, in cells that produce mucus
    • Squamous cell carcinoma – typically found in the airways of the lungs
    • Large cell undifferentiated carcinoma – this type of cancer can not be classified as either adenocarcinoma or squamous cell carcinoma.
  • Small cell lung cancer (SCLC) – this type of lung cancer tends to spread faster than NSCLC, however it is less common than NSCLC, accounting for approximately 15% of all lung cancers.1

Lung cancer is the second and third most common cancer in males and females in Singapore respectively.11

Is lung cancer hereditary?

For most lung cancer cases, genetic mutations are somatic (meaning they happen in cells only specific to that individual and are not inherited).4

In rare cases, genetics may play a role in the development of lung cancer, particularly for people who have inherited gene mutations on chromosome 6 (which accounts for approximately 6% of all DNA in cells).2,3

However the most common cause of lung cancer is cigarette smoking. 1

Stages of lung cancer

The stages of lung cancer are classified by the TNM system which stands for: 7

  • Tumour (T) – describes the size of the tumour and the extent the cancer has spread into the tissue of the lung. The tumour can be graded from T1a (which describes a tumour under 1cm) to T4 (which describes a tumour larger than 7cm).
  • Nodes (N) – describes whether the tumour has spread to nearby lymph nodes. Nodes can be graded from N0, where there has been no spread, through to N3, where the cancer has spread to other areas of the body, such as the other side of the chest or collarbone.
  • Metastasis (M) – describes whether the cancer has spread to other areas of the body outside of the lung. Metastasis can be graded from M0, where there has been no spread through to M1c, where the cancer has spread to other organs of the body and produced additional tumours.

Signs and symptoms of lung cancer

There are a number of conditions that can cause the below symptoms besides lung cancer; however, it is important to see your doctor and discuss your individual symptoms. Seeking treatment as soon as you notice symptoms will enable the best chance for successful treatment. 6

Some common symptoms of lung cancer include: 5

Difficulty breathing, wheezing or coughing

Difficulty swallowing

Coughing up blood

Unexplained tiredness or fatigue

Swollen face

or enlarged veins in the neck

A chronic (ongoing) cough

that doesn’t go away

Shoulder or chest pain

that may be worse with breathing

Chronic infections

such as bronchitis or pneumonia

Some lung cancers can also cause a collection of specific symptoms which are termed syndromes. Syndromes which have been associated with lung cancer include:

  • Superior Vena Cava (SVC) syndrome – the SVC is a large blood vessel that carries blood away from the head and arms to the heart. Tumours near the lung area can press against this large blood vessel causes swelling in the face and neck, chest and upper arm area.6
  • Paraneoplastic syndromes – some lung cancers make substances which act like hormones and can affect other tissues and organs in the body. Some paraneoplastic syndromes include:
    • Cushing Syndrome – adrenal glands in the body may produce too much cortisol (due to cancer cells producing specific hormones), this can lead to weight gain, as well as symptoms of dizziness/tiredness and weakness.6
    • SIADH (Syndrome of inappropriate anti-diuretic hormone) – cancer cells can make a hormone which encourage the kidneys to hold onto water, reducing the amount of salt in the blood. Symptoms can include; cramps and muscle weakness, tiredness, nausea and/or vomiting. In severe cases without treatment, seizures and coma may occur.6

Treatment for lung cancer

Frequently asked questions

Are there risk factors for lung cancer?

Exact causes of lung cancer are not fully known, especially in those people who develop lung cancer without any known risk factors. 1

However, there are a number of lifestyle-related factors which increase the risk of developing lung cancer, including: 8

  • Smoking and vaping – cigarette smoking carries a significantly higher risk of developing lung cancer when compared with non-smokers. It is estimated that lung cancer cases as a result of cigarette smoking contribute to 90% of all cases in men and 65% in women. While e-cigarettes and vaping remain relatively new and research is still being done to identify the long-term health effects, they have been shown to pose significant health risks with some substances found in e-cigarette vapor linked to an increased risk of cancer.
  • Second-hand smoking – there is an increased risk for non-smoking people who breath in the cigarette smoke of others. Living with someone who smokes can increase your risk for lung cancer by approximately 20-30%. 1
  • Exposure to asbestos and other toxins – people who have been exposed to asbestos (traditionally used in building materials) and other toxins such as radon (a radioactive gas used in the mining industry) have an increased risk of developing lung cancer.1

Additional risk factors include:

  • Age – the risk of developing lung cancer increases as people age. Most lung cancers are diagnosed in people over the age of 60.1
  • Medical history – for people who have a medical history of lung disease such as emphysema or fibrosis of the lung may have an increased risk of developing lung cancer. 1


For a full list of references, click here.
  1. Cancer Council. (2018). Lung Cancer. Retrieved on 22nd April 2019 from
  2. American Cancer Society. (2016). What causes non-small cell lung cancer? Retrieved on 22ndApril 2019 from
  3. Genetics Home Reference. (2019). Chromosome 6. Retrieved on 22nd April 2019 from
  4. Genetics Home Reference. (2019). Lung Cancer. Retrieved on 22nd April 2019 from
  5. Australian Government: Cancer Australia. (2018). Lung Cancer. Retrieved on 22nd April 2019 from
  6. American Cancer Society. (2016). Signs and Symptoms of Lung Cancer. Retrieved on 22nd April 2019 from
  7. Cancer Council. (2018). Staging and prognosis for lung cancer. Retrieved on 22nd April 2019 from
  8. Australian Government: Cancer Australia. (2018). What are the risk factors for lung cancer?Retrieved on 25th April 2019 from
  9. Australian Government: Cancer Australia. (2014). Risk factors for lung cancer: an overview of the evidence. Retrieved on 25th April 2019 from
  10. Australian Institute of Health and Welfare. (2011). Lung cancer in Australia: an overview. Retrieved on 7th November 2019 from
  11. Singapore Cancer Society. (2016). Lung Cancer. Retrieved on 26 March 2020 from

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