How is cancer diagnosed?

This section describes the most common tests that a child might have to investigate their symptoms and diagnose their cancer.

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Medical history and physical examination

A medical history and physical examination are basic tools used to help diagnose diseases, including cancer.

A medical history is a description of your child’s health throughout their life. The doctor will ask about your child’s current and past health, including any surgery, immunisations, accidents, symptoms and illnesses. Because some cancers run in the family, the doctor will also ask about your family medical history.

Giving a complete and accurate medical history is very important because it helps the medical team decide on the types of tests needed, as well as the best treatment program.

In a physical examination, the doctor will examine various parts of the child’s body to check for any abnormalities, such as lumps and bumps, or to see if there is any pain. They will also listen to the child’s heart and lungs, and check the child’s nervous system by testing muscle strength and tone, reflexes, vision, sensation and hearing.

Physical examinations and medical histories cannot be used on their own to diagnose cancer. They help the doctor decide which other diagnostic tests need to be done.

Blood tests

Blood tests are important to help diagnose many types of cancer, and to check for general health and organ function. Some cancers produce compounds (called cancer markers or tumour markers) that can be detected in the blood. If tumour markers are found in the blood, the child will have other tests to determine whether they have cancer.

To do a blood test, a small needle will be placed in your child’s arm (usually in a vein on the inside of their elbow), and the doctor will collect a small amount of blood to be tested in a laboratory.

The most common blood tests are:

full blood count (FBC, also known as a complete blood count or CBC). This test measures the numbers of different cell types in the blood, including white blood cells, red blood cells and platelets. Cell counts that are too high or too low can indicate disease, such as cancer
blood chemisty. These tests measure the levels of different substances in your child’s body, including minerals, enzymes, hormones and waste products. The tests are used to check whether organs – such as the kidneys, liver, lungs and heart – are functioning properly. They are also used to see if any tumour markers are present.

Your child might have several blood tests at different times. If the diagnosis is confirmed, more blood tests will be needed during and after treatment.

Because the blood tests need to be done in special laboratories, it can sometimes be a few days before you find out the results.

Urine tests

Urine tests can be used to check that your child’s liver or kidneys are working properly, and to check for tumour markers.

Your child will be asked to urinate (wee) into a plastic cup. If the child is not yet toilet trained, a bag will be placed in their nappy to collect the urine.

The urine will be 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 can be used, depending on what type of cancer is suspected and where it is in the body. The doctor uses these tests to determine exactly where the cancer is, how big it is and whether it has spread.

In many cases, several different types of medical imaging tests are done to get an accurate diagnosis.

Medical imaging itself is not painful, but, for some tests, your child may need to be given a contrast agent – a dye that helps to give a clearer picture. In some cases, this is an injection; in others, it is a liquid for the child to drink.

In very rare cases, the contrast agent may cause an allergic reaction. If your child has ever had a reaction to contrast agents or dyes before, or has any allergies (especially to iodine), be sure to let the health professionals know.

For most medical imaging tests, the child has to be very still while the images are being taken. This can be difficult for children, especially young children. Encourage your child to stay very still during the tests so the health professionals can take good images. Infants or young children may be given a medicine (a sedative) to calm them down and help them stay still, or may be given a general anaesthetic so that they sleep through the test.

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

Because medical imaging scans are complex and detailed, 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 there is cancer in the lungs or around the heart.

X-rays are painless. Your child will be asked to stand in front of the X-ray machine and keep very still while the images are being taken.

Sometimes, depending on the type of cancer that is suspected, 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 a very important tool for diagnosing cancer. The amount of radiation that your child is exposed to during an X-ray is very small. However, because X-rays are a type of radiation, there is an extremely small chance that they can contribute to the development of cancer. This risk is very low, but, if you are concerned about it, 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. It is a completely painless test. The doctor will let you know if there is anything your child needs to do to prepare for the ultrasound.

During the ultrasound procedure, a small wand is covered with gel and then moved slowly over your child’s body part. There is no pain, but the wand may be pressed down firmly to get a better picture, which might be uncomfortable.

Your child might need a follow-up CT scan or MRI if the ultrasound suggests that there is a tumour or growth. These other scans can confirm what the ultrasound found.

The sound waves used in an ultrasound cannot be heard by the human ear. They are completely safe, and there are no long-term effects or risks to your child.

Computed tomography (CT) scan

CT scans (also called CAT scans) are a very complex series of X-rays that provide a highly detailed picture of the inside of the body. CT scans can be used to create three-dimensional 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 health care team decide on the best treatment.

A CT machine is shaped like a large doughnut ring 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.

Because the child needs to stay very still during the scan, they may be given a medicine (a sedative) before the scan to keep them calm. If the child is young or nervous, they may be given a general anaesthetic so that they sleep through the scan.

CT scans are painless.

Contrast agents are often used for CT scans. These make soft tissues and organs appear on the image, as well as bones. Contrast agents can be given as an injection or a drink, or both may be given.

The amount of radiation that your child is exposed to during a CT scan is very small, but more than the amount of radiation from a standard X-ray. Because X-rays are a type of radiation, there is an extremely small chance that they can contribute to the development of cancer. This risk is very low, but, if you are concerned about it, discuss it with your child’s doctor.

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

Magnetic resonance imaging (MRI)

MRI scans use radio waves and magnets to create an image of the inside of the body.

An MRI can provide specific information about the body that other scans may not detect. 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 health care team decide on the best treatment.

An MRI machine is shaped like a long, narrow tube. Your child will be asked to lie very still on a table that slides into the tube. This might be distressing for the child, especially if they are not comfortable with closed or confined spaces. The machine also makes loud noises, which can be scary for children. Your child will be given earplugs or headphones to block out these noises.

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.

You will be able to talk to your child through an intercom during the scan, which can help them relax.

MRI scans are painless.

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 given as an injection.

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.

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 health care team decide on the best treatment.

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

A PET scanner is similar in shape to a CT scanner. It is 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 by the ring. 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, and the risk to your child from exposure to the radioactivity is very low. 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, a particular type of cancer in children. MIBG is a radioactive dye that attaches specifically to neuroblastomas 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 one day and will have the scan the next day. The scan takes about 90 minutes. Your child might need more than one scan over a day or two, but they will only need one 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 be asked to lie on a table while a ring-shaped camera moves back and forth over their body.

MIBG scans are painless.

Bone scan

Bone scans provide specific and 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 later, they will have 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 on a table while a ring-shaped camera moves back and forth over their body. The scan takes about an hour.

Because the child needs to stay very still during the scan, they may be given a medicine (a sedative) before the scan to keep them calm.

Bone scans are painless.

Biopsy

A biopsy procedure involves a doctor taking a sample of the tumour or mass to be looked at under a microscope. This is the most reliable way to tell if cells are cancerous.

The sample from the tumour can be collected in several ways, depending on where the tumour is and the tests that need to be done on it:

Fine needle aspiration biopsy is where a very thin needle and syringe are used to remove some fluid for testing.
Core needle biopsy is where a thick needle is used to remove a sample of tissue, such as part of a tumour.
Surgical biopsy is where a surgeon removes part (incisional biopsy) or all (excisional biopsy) of a lump as part of a surgical procedure. 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, the sample will be sent to a pathologist, who will examine it under a microscope. The pathologist will do specialised diagnostic tests to determine whether the sample contains cancerous cells. This will take several days.

Because a biopsy is a (usually very minor) surgical procedure, which can be painful, your child will usually be given a general anaesthetic, which will put them to sleep so that they do not feel any pain during the procedure. Very rarely, in older children, the biopsy might be done with a local anaesthetic, which numbs the area around the biopsy to prevent pain.

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

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 the doctor thinks they have a type of blood cancer (such as leukaemia), or another cancer that may have spread to the bone marrow.

Because bone marrow samples need to be sent to a laboratory for analysis, it usually takes 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, the 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. This is why children are given a general anaesthetic to put them to sleep so that they do not 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, and both procedures are done in around 10 minutes.

Your child will have a general anaesthetic so that they sleep through the procedure and do not feel pain.

Lumbar puncture

Sometimes, cancers such as leukaemia can spread into the fluid around the brain and spine. This fluid is called cerebrospinal fluid (CSF). In these cases, it is important to take a sample of the fluid to see if it contains cancer cells. This is done by a procedure called a lumbar puncture.

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 health care team will use the results of a lumbar puncture to guide treatment options.

A lumbar puncture is often called a ‘spinal tap’. It is similar to bone marrow tests, except 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. The procedure takes around 20 minutes.

Lumbar punctures are painful, and your child needs to stay still during the procedure. The doctor may give your child either a general anaesthetic (to put them to sleep so that they don’t feel any pain) or another drug for ‘conscious sedation’ (where your child will be awake during the procedure but will feel no pain).

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

The sample of CSF is sent to a pathologist, who will look at it under a microscope. The pathologist will determine whether the sample contains cancerous cells. Part of the sample may also be sent to a laboratory to check for tumour markers. It usually takes a few days for you to find out the results.

More information

The Royal Children’s Hospital Melbourne has videos that show children having some of these diagnostic tests, as well as helpful 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 provides tips to help children prepare for the tests.