Diagnosis and tests

How is cancer diagnosed?

When a child has been diagnosed with cancer or a cancer is suspected, they will undergo a series of tests to find out what is happening inside their body.

The tests may feel like an unnecessary delay causing a worrying wait but by having accurate information about the type and stage of the child’s illness, the Consultant can plan the best individual treatment for them.

The tests will also find out about the child’s general health, which may also influence what type of treatment they receive.

Below is a list of the most common tests that are used to diagnose cancer. Parents can speak to their child’s care team if they are unsure about why any of these tests are being performed. The information is provided for general guidance only. Please scroll down the page, or use the quick links below.

This involves removing a small part of the tumour either with a specially designed needle (a needle biopsy), or during a small operation (open biopsy). The sample of the tumour is tested in a laboratory to discover what type of tumour it is. Most but not all suspected tumours will be biopsied.

Bone marrow is the spongy tissue found in the middle of certain bones. It is the ‘factory’ that produces the body’s blood cells. It contains stem cells (or ‘mother’ cells) which develop into one of the three different types of blood cell:

• Red – which carry oxygen around the body
• White – which fight infection
• Platelet – which form clots to control bleeding and bruising.

Leukaemia and other types of cancer affect the bone marrow. To find out if this has happened, a needle is put into the bone and a small amount of bone marrow is removed. This test is usually done under sedation or general anaesthetic.

From this the specialists will be able to study the type of cells in the bone marrow to see if any are leukaemic (malformed or immature and rapidly reproducing) or if there is an imbalance of cells being produced.

This test is also used to see if a cancer has spread into the bone marrow and to assess how treatment is progressing.

A bone marrow aspirate can sound like an unpleasant test for a child to undergo.  Most parents report however, that there are few, if any after-effects of the test.

Blood tests are usually carried out before, during and after treatment. The blood taken is often tested for many different reasons including to assess if the child has an infection, to test how the systems in their body are working (such as liver function) and to match the child’s blood to a donor’s blood in case a transfusion is needed.

Also, certain tumours send out hormones or proteins that can be detected in the blood. These are known as 'tumour markers'. Because of these, a blood test will be used to detect certain types of tumour and also to see if the tumour is responding to treatment.

Blood will also be tested for its ‘blood count’ – which shows the number of red, white and platelet cells present in the blood. A reduction of the total number of blood cells is a common side-effect of treatment and will be monitored regularly.

For more information on blood counts and how chemotherapy can affect them, visit our section on chemotherapy side-effects.

This is a procedure that tests the fluid surrounding the spinal cord to see if it contains any cancer cells. The fluid is known as the cerebrospinal fluid (as it surrounds the spinal cord and the brain). A needle is inserted between two bones in the lower spine to draw out a few drops of the fluid for analysis.  This is usually done when the child is under general anaesthetic.

A lumbar puncture is often used to diagnose leukaemia, lymphoma and occasionally brain tumours. It is also used to test if cancer cells have spread into the fluid from elsewhere.
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X-rays are used when there is a suspected tumour in the chest, bones and tummy area. Tumour tissue can look very different to healthy tissue in an X-ray. However, sometimes tumour tissue looks normal on an X-ray so doctors have a variety of scans that they can use to get a more detailed picture.

This scan lets the doctors view the soft tissues of the body. It is painless but because the child will have to lie still, a sedative or general anaesthetic may be given.

The child lies in a narrow tunnel within the machine whilst the scan is taking place. The magnetic waves the scanner uses create a detailed image of inside their body. As the machine can be noisy, a sedative or general anaesthetic may be given to help a child stay still. Soothing music or sounds can be played through headphones to help relax them too. Though the scan may be daunting, it is completely painless.

This scan turns sound waves (that we cannot hear) into pictures that reveal the presence of unhealthy tissue. They are commonly used to look at the heart or the tummy area.

This scan involves small amounts of radioactive substances being injected into the vein which travel into abnormal areas of bone. The scan will then show how much of the bone is affected by a tumour.