How do we test for cancer?

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If a patient has symptoms that indicate they may have cancer, their doctor will perform a series of tests to find out more. The doctor will perform tests to confirm whether cancer or another disease is causing the symptoms.1 If cancer is diagnosed, then the doctor will conduct additional tests to identify where the cancer is growing and how advanced its growth is.2 They may also perform tests to identify additional biomarkers of the cancer, which give doctors an indication as to what is driving the cancer’s growth and how best to treat it.3

Diagnosing the presence of cancer

In order to diagnose cancer, a doctor will usually begin by asking their patient questions, including about: 1

  • Their medical history. For example, the types of symptoms they are experiencing and how long they have been experiencing these symptoms.
  • Their family’s medical history. For example, whether or not other family members have had cancer.

The doctor may also perform a physical examination. 1 For example, cancerous tumours may produce a lump that the doctor can feel during a physical examination. If a woman has breast cancer, the doctor may be able to feel a lump in her breast.4

If these tests indicate the patient has cancer, additional tests that may be performed include:

  • Laboratory tests of the patient’s blood, urine, stool or other body fluids. The composition of these fluids can give the doctor clues regarding whether or not the patient has cancer, and if so what type of cancer they have. However, abnormal lab results alone are not sufficient for a cancer diagnosis. Lab tests are a useful tool, but other tests will be needed. 1
  • Imaging tests enable the doctor to look inside the patient’s body. These scans may produce images of the internal organs, or enable the doctor to view internal processes such as the flow of substances through the body. 1 They include:
    • Computer assisted x-rays (also called computed tomography scans): An x-ray machine linked to a computer produces detailed images of the internal organs which are suspected to be affected by cancer. Often a dye is used to increase the contrast between the organs of interest and other body parts.1
    • Ultrasound: A device which sends out inaudible sound waves is attached to a computer. The ultrasound device directs sound waves to the internal structures being studied. The computer produces images of the internal structures, based on the echoes of these inaudible sound waves.1
    • Medical resonance imaging (MRI): A strong magnet attached to a computer is used to excite electrical charges in body fluid. When the magnet is removed, studying how the electric charges return to normal enables the computer to produce three-dimensional images of internal structures.5
  • Tissue biopsy involves removing cells from the body and testing them in a laboratory to see if they are cancerous. 1 Depending on the location and amount of tissue required, a biopsy may be taken by:
    • Needle: A hollow needle is inserted through the skin to the location of the tissue that will be tested for cancer. The doctor can then extract the tissue sample by drawing it up through the hollow needle.6
    • Endoscope, which is a lighted tube. When the cancer is located within a body cavity such as the mouth or rectum, the doctor may insert an endoscope into the cavity and remove the tissue sample for biopsy via the tube.1
    • Surgery: The entire cancer tumour (an excisional biopsy) or part of the tumour (an incisional biopsy) may be removed using surgical techniques.1

The results of a number of these tests can be used to inform doctors about the stage of the cancer growth.7

 

References

  1. National Cancer Institute. About cancer: Diagnosis. 2015 (cited 11 December 2016). Available from: [URL link]
  2. National Cancer Institute. About cancer: Staging. 2015 (cited 11 December 2016). Available from: [URL link]
  3. Henry NL, Hayes DF. Cancer biomarkers. Mol Oncol. 2012;6(2):140-6. [Full text]
  4. Australian Government Cancer Australia. Breast cancer. 2017 (cited 11 April 2017). Available from: [URL link]
  5. National Institutes of Biomedical Imaging and Bioengineering. Medical resonance imaging (MRI). 2017 (cited 11 April 2017). Available from: [URL link]
  6. Mayo Clinic. Needle biopsy. 2015 (cited 11 April 2017). Available from: [URL link]
  7. Cancer Research UK. Stages of cancer. 2014 (cited 11 April 2017). Available from: [URL link]
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