How is cancer diagnosed?

Cancer in children can be hard to recognise because some symptoms may be similar to more common illnesses or injuries. Your doctor may need to do a number of tests to determine that your child’s symptoms are related to cancer.

Below is information about the most common tests a child may have in order to diagnose cancer.

Medical history and physical examination

A medical history and physical exam are basic tools used to help diagnose many conditions, including cancer.

A medical history is a description of your child’s health throughout their life. Your doctor will ask about your child’s current and past health, such as:

surgeries
immunisations
accidents
symptoms
illnesses.

Because some cancers run in the family, the doctor will also ask about your family medical history.

It’s important to give as complete and accurate medical history as you can. This helps the doctors decide on the types of tests needed, as well as the best treatment program for your child.

In a physical exam, the doctor will:

examine your child’s body to check for any abnormalities, such as lumps and bumps, or to check if there is any pain
listen to your child’s heart and lungs
check your child’s nervous system by testing
- muscle strength and tone
- reflexes
- vision
- sensation
- hearing.

A physical examination and medical history does not diagnose cancer. Rather, it helps the doctor decide what other diagnostic tests need to be done.

Blood tests

Blood tests are important to help diagnose many types of cancer. Blood tests are also used to check for general health and organ function.

Some cancers produce substances (called cancer markers or tumour markers) that can be detected in the blood. If the blood tests show tumour markers, your child will have other tests to determine if they have cancer.

To do a blood test, the doctor will insert a small needle in your child’s arm (usually in a vein on the inside of their elbow). The doctor will collect a small amount of blood to be tested in a laboratory. The blood test shouldn’t be painful but might be cause a little discomfort to your child initially.

Your child may have several blood tests at different times. If your child does have cancer, they will need to have more blood tests during and after treatment.

Blood samples need to be sent to a special laboratory to check them. It can sometimes be a few days before you find out the results.

The most common blood tests are a full blood count and blood chemistry.

You can find links to further support and advice at our Find support and more information page.

Full blood count (FBC)

A full blood count (FBC) is sometimes called a complete blood count (CBC). This test measures the numbers of different cell types in the blood, including;

white blood cells
red blood cells
platelets.

Cell counts that are too high or too low can indicate cancer.

Blood chemistry

Blood chemistry tests measure the levels of different substances in your child’s body, including:

minerals
enzymes
hormones
waste products
tumour markers (sometimes called biomarkers).

Doctors use these tests to check whether organs are functioning properly. This could include the kidneys, liver, lungs and heart.

Urine Tests

Doctors may use urine tests to check if your child’s liver or kidneys are working properly. Tumour markers may also show up in a urine test.

Your child will need to urinate (wee) into a plastic cup. If your child is not yet toilet trained, you can use a special bag that can be placed in their nappy to collect the urine.

The urine sample is tested in a laboratory, and the results may take a few days to come back.

Medical imaging

Medical imaging is a very important tool to diagnose cancer. It involves taking a picture (scan) of the inside of your child’s body. Several different types of imaging might be used, depending on the type of cancer and where it’s located in the body. These tests help to determine:

exactly where the cancer is
how big it is
whether it has spread.

In many cases, your doctor will order several different types of medical imaging tests to get an accurate diagnosis.

Medical imaging itself isn’t painful. However, for some tests, your child may need to be given a dye that helps to give a clearer picture. This dye is called a contrast agent. In some cases, the dye may need to be injected; in others, it is in liquid-form for your child to drink. If your child needs an injection, they should only experience a small amount of discomfort (if any), as the needle is inserted.

In very rare cases, the contrast agent may cause an allergic reaction. For this reason, it’s important to advise your doctor if your child has:

ever had a reaction to contrast agents or dyes before
any allergies, especially to iodine.

Most medical imaging tests will require your child to remain very still while the images are being taken. This can be difficult for some children, especially young ones. However, explaining to your child that it’s important they remain still so the doctor can take clear pictures may help. In some cases, infants or young children may be given a sedative (medicine to calm them down and help them stay still). Other children may be given a general anaesthetic so that they sleep through the test.

Some medical imaging tests use small amounts of radiation or radioactivity to give a picture of the inside of the body. Tests such as X-rays and CT scans use radiation and are done in radiology departments. Tests such as PET scans, MIBG scans and bone scans use radioactivity, and are done in nuclear medicine departments.

Medical imaging scans are complex so it will be a few days before you find out the results.

X-ray

X-rays are a type of radiation that are used to look inside the body. They create a black-and-white picture of the inside of the body.

X-rays can help diagnose different types of cancer, such as bone cancer. Chest X-rays are used to see whether cancer is in the lungs or around the heart.

In order to get a clear picture, it will be important for your child to remain still while the x-rays are being done. The radiographer will show your child the correct position before taking the X-ray.

X-rays are painless. However, your child might be given a contrast agent to make other body structures (e.g. their bladder or stomach) appear on the X-ray. Contrast agents for X-rays are usually given as a liquid for the child to drink.

X-rays are an important tool for diagnosing cancer, however they do give off a very small amount of radiation. There is an extremely small chance that an X-ray can increase the risk of cancer in the future, but this risk is very low. If you are concerned, make sure you discuss it with your child’s doctor.

Ultrasound

Ultrasound uses sound waves to create black-and-white images of the inside of the body. It can be used to detect lumps, masses or tumours. The doctor will let you know if there is anything your child needs to do to prepare for the ultrasound.

During the ultrasound, a small wand is covered with gel and then moved slowly over the area of your child’s body that is being investigated.

Ultrasound is painless, but the wand may be pressed down firmly to get a better picture. This may be uncomfortable.

If the ultrasound suggests that there is a tumour or growth, your child might need a follow-up CT scan or MRI to confirm what the ultrasound found.

This kind of test is completely safe. The sound waves used in an ultrasound can’t be heard, and there are no long-term effects or risks to your child.

Computed tomography (CT) scan

CT scans (also called CAT scans) are a complex series of X-rays that provide a very detailed picture of the inside of the body. CT scans can be used to create 3D images.

CT scans are used to:

detect abnormal growths, including tumours, in the body
determine the stage of a tumour (how big it is and whether it has spread)
guide where a biopsy should be taken
help the doctors decide on the best treatment.

A CT machine is shaped like a large doughnut with a table that slides in and out of the middle. The ring contains the X-ray machine.

Your child will be asked to lie very still on the table while the images are being taken. Infants or young children may be given a sedative (medicine to calm them down and help them stay still). Some children may be given a general anaesthetic so that they sleep through the test.

A CT scan will show your child’s bones. If your doctor also wants to see soft tissues and organs on the CT scan, your child may need to take a contrast agent. Contrast agents can be given as an injection or a drink, or both.

CT scans are painless. However, an injection of contrast agent may cause a little discomfort when the needle is inserted.

CT scans are a type of X-ray, and X-rays give off radiation. CT scans give off a small amount of radiation, but more than the amount of radiation from a regular X-ray. There is an extremely small chance that a CT scan can increase the risk of cancer in the future. This risk is very low. However, if you are concerned about it, discuss it with your child’s doctor.

The Australian Radiation Protection and Nuclear Safety Agency has further information on:

Medical resonance imaging (MRI)

MRI scans use radio waves and magnets to create an image of the inside of the body. An MRI machine is shaped like a long, narrow tube.

An MRI can provide information about the body that other scans may not be able to. MRIs are used to:

detect abnormal growths, including tumours, in the body
help determine the stage of a tumour (how big it is and whether it has spread)
help the doctors decide on the best treatment.

Your child will need to lie very still on a table that slides into the tube. The actual MRI is painless however, your child may find being in a confined space distressing. The machine also makes loud noises, which can be scary or overwhelming for kids. However, your child can wear earplugs or headphones to help block out these noises.

If your child is anxious, reassure them that you will be able to talk to them through an intercom during the scan. This may help them relax. Infants or young children may be given a sedative (medicine to calm them down and help them stay still). Some children may be given a general anaesthetic so that they sleep through the test.

MRI scans take longer than X-rays or CT scans, and your child might need to be in the machine for up to an hour, depending on the parts of the body that need to be scanned. If your child is anxious, speak to the technician about your concerns.

Contrast agents are often given before an MRI scan, which can make different parts of the body stand out better in the image. These are usually injected. You child may experience some discomfort when having the injection.

The Royal Children’s Hospital Melbourne has videos that show children having some of these diagnostic tests. It also has some tips for parents to reduce their child’s discomfort during the tests. There is also a section on medical imaging, including photos.

Positron emission tomography (PET) scan

PET scans use radioactivity to create images of the body. Before the scan, your child will be injected with a very small amount of radioactivity. Because cancer cells tend to absorb more radioactivity than normal cells, they will look different on the scan.

PET scans are painless, although your child may experience some discomfort when receiving the injection.

A PET scan is used to:

detect cancer
help determine the stage of a tumour (how big it is and whether it has spread)
help the doctors decide on the best treatment.

PET scans are used with other types of imaging, to provide a better picture of what is happening in your child’s body.

A PET scanner is shaped like a CT scanner. It’s a ring-shaped machine that slides back and forth over a table. Your child will be asked to lie very still on the table while the images are being taken.

Infants or young children may be given a sedative (medicine to calm them down and help them stay still). Some children may be given a general anaesthetic so that they sleep through the test. The scan can take up to an hour.

The radioactivity given to your child before the scan only stays in their body for a short time. The risk to your child from exposure to the radioactivity is very low. However, if you are concerned about this risk, discuss it with your child’s doctor.

Metaiodobenzylguanidine (MIBG) scan

An MIBG scan is a test used to diagnose neuroblastoma. MIBG is a radioactive dye that attaches to neuroblastoma cells anywhere in the body, so they can be easily seen on a scan.

If your child needs an MIBG scan, they will have an injection of MIBG on the first day and will have the scan the next day. The scan takes about 90 minutes. Your child might need more than 1 scan over 1 or 2 days, but they will only need 1 injection of MIBG. They will also need to drink a small amount of liquid that contains iodine 2 days before and 4 days after the MIBG scan.

The scanner looks similar to a CT scanner or a PET scanner. Your child will need to lie very still on a table while a ring-shaped camera moves back and forth over their body.

MIBG scans are painless, although your child may experience some discomfort when receiving the injection.

Bone scan

Bone scans provide detailed information about your child’s bones. They are used to diagnose bone cancer and to determine whether a cancer has spread to the bones. They can also help to diagnose other bone disorders or injuries.

If your child needs a bone scan, they will first have an injection of a radioactive dye a few hours prior to having the scan. The radioactivity settles in areas of damaged bone, which appear as ‘hot spots’ on the scan.

The machine is very similar to a CT scanner. Your child will be asked to lie very still on a table while a ring-shaped camera moves back and forth over their body. The scan takes about an hour.

Infants or young children may be given a sedative (a medicine to calm them down and help them stay still). Some children may be given a general anaesthetic so that they sleep through the test.

Bone scans are painless, although your child may experience some discomfort when receiving the injection.

You can find links to further support and advice at our Find support and more information page.

Biopsy

A biopsy is done so that a doctor can look at a piece of tumour or cells under a microscope. This is the most reliable way to tell if cells are cancerous.

The doctor may collect the sample in 3 ways. Collection depends on where the tumour is, and which tests need to be done on it:

Fine needle aspiration biopsy. A very thin needle and syringe are used to remove some fluid for testing.
Core needle biopsy. A thick needle is used to remove a sample of tissue, such as part of a tumour.
Surgical biopsy. A surgeon removes part (incisional biopsy) or all (excisional biopsy) of a lump as part of a surgery. A needle biopsy is usually done first to make sure the surgery is necessary.

Doctors often use medical imaging (such as a CT scan, MRI or ultrasound) to help determine where to take the biopsy from.

After the biopsy is taken, a pathologist will look at it under a microscope. The pathologist will test the sample to see if it contains cancerous cells. It will take several days before your get the test results back.

A biopsy is usually a minor surgical procedure. However, it can be painful, so your child will usually be given a general anaesthetic. This will put them to sleep so that they don’t feel any pain during the procedure. Very rarely, in older children, the biopsy might be done with a local anaesthetic. This numbs the area around the biopsy to prevent pain.

Your child will probably have some soreness in the biopsy area afterwards, and they might need to stay in hospital for a short time to recover.

You can find links to further support and advice at our Find support and more information page.

Bone marrow tests

Bone marrow produces blood cells, including red blood cells, white blood cells and platelets. Bone marrow is found inside the large bones in the body, such as the pelvic bone (the hips). It consists of liquid parts and solid parts.

Your child might have a bone marrow test if your doctor thinks they have a type of blood cancer (such as leukaemia). Your doctor might also use this test to see if cancer has spread to the bone marrow.

Bone marrow samples need to be sent to a laboratory for analysis, so it will usually take a few days for you to find out the results.

Bone marrow tests are almost always done under a general anaesthetic, where your child is asleep.

Bone marrow biopsy

A bone marrow biopsy involves removing a piece of the solid part of the bone marrow from inside a bone, usually the pelvic bone. During the procedure, your doctor will insert a thick needle into the bone to remove a sample of bone marrow. The procedure usually takes less than 10 minutes.

Bone marrow biopsies are painful, which is why children are given a general anaesthetic to put them to sleep so that they don’t feel pain during the procedure.

It is normal for the biopsy site to be bruised and sore for a few days.

Bone marrow aspiration

For a bone marrow aspiration, the doctor will insert a fine needle into a bone (often the pelvic bone) and remove some of the liquid part of the bone marrow. This is done at the same time as a bone marrow biopsy. Both procedures are done in around 10 minutes.

Your child will have a general anaesthetic so that they sleep through the procedure and don’t feel pain.

You can find links to further support and advice at our Find support and more information page.

Lumbar puncture

A lumbar puncture is often called a ‘spinal tap’.

Some cancers can spread into the fluid around the brain and spine. This fluid is called cerebrospinal fluid (CSF). A doctor will use a lumbar puncture to collect the CSF.

Cancer cells or tumour markers in the CSF indicate whether a brain or spinal cord tumour, or another cancer such as leukaemia, has spread to the CSF. The doctors will use the results of a lumbar puncture to guide treatment options.

A lumbar puncture is similar to bone marrow tests. The difference is that the needle is inserted into the lower back, between the bones of the lower part of the spine (also called the lumbar spine), to remove a sample of CSF. This procedure takes around 20 minutes.

Lumbar punctures are painful, and your child needs to stay still during the procedure. Your doctor may give your child either:

a general anaesthetic, to put them to sleep so that they don’t feel any pain, or
another medicine for ‘conscious sedation’, where your child will be awake during the procedure but will not feel pain.

Your child may also need to lie on their back for up to an hour after the procedure to reduce the chance of developing a headache.

A pathologist will look at the sample under a microscope to determine whether the sample contains cancerous cells. Part of the sample may also be sent to a laboratory to check for tumour markers. It will usually take a few days for you to find out the results.

You can find links to further support and advice at our Find support and more information page.

More information

The Royal Children's Hospital Melbourne has videos that show children having some of these diagnostic tests. It also has some tips for parents to reduce their child's discomfort during the tests. There is also a section on medical imaging, including photos.

Lab Tests Online also has tips to help children prepare for the tests.

The Australian Radiation Protection and Nuclear Safety Agency has fact sheets on CT imaging and children, and what parents should know about CT scans.

You can find links to further support and advice at our Find support and more information page.

About children’s cancer