Childhood Cancer: Diagnosis

Approved by the Cancer.Net Editorial Board, 01/2022

ON THIS PAGE: You will find a list of common tests, procedures, and scans that doctors use to find the cause of a medical problem. Use the menu to see other pages.

Doctors use many tests to find, or diagnose, cancer. They also do tests to learn if cancer has spread to another part of the body from where it started. If the cancer has spread, it is called metastasis. Doctors may also do tests to learn which treatments might work best.

For most types of cancer, a biopsy is the only sure way for the doctor to know if an area of the body has cancer. In a biopsy, the doctor takes a small sample of tumor tissue for testing in a laboratory. If a biopsy is not possible, the doctor may suggest other tests that will help make a diagnosis.

How childhood cancer is diagnosed

There are many tests used for diagnosing childhood cancer. Your child’s doctor may consider these factors when choosing a diagnostic test:

  • The type of cancer suspected

  • Your child’s signs and symptoms

  • Your child’s age and general health

  • The results of earlier medical tests

Not all tests described here will be used for every person. If possible, it is important to have tests done in a pediatric specialty center where tests can be supervised by pediatric specialists. These are medical professionals who specialize in diagnosing and treating younger patients. In addition to a physical examination, the following tests may be used to diagnose childhood cancer:

  • Blood tests. Routine blood tests measure the number of different types of cells in a person’s blood. Levels of certain cells that are too high or too low can indicate the presence of certain types of cancer.

  • Biopsy. A biopsy is the removal of a small amount of tissue for examination under a microscope. Other tests can suggest that cancer is present, but only a biopsy can make a definite diagnosis, except for certain types of brain tumors. A biopsy can be guided by imaging tests (such as a computed tomography (CT) or magnetic resonance imaging (MRI) scan; see below) to make the procedure accurate and precise. The type of biopsy performed depends on the location of the tumor and part of the body involved. The sample removed during the biopsy is analyzed by a pathologist. A pathologist is a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease.

  • Bone marrow aspiration and biopsy. These 2 procedures are similar and often done at the same time to examine the bone marrow, which is the spongy, fatty tissue found inside larger bones. Bone marrow has both a solid and a liquid part. A bone marrow aspiration removes a sample of the fluid with a needle. A bone marrow biopsy is the removal of a small amount of solid tissue using a needle.

    A pathologist then studies the samples in a lab. A common site for a bone marrow aspiration and biopsy is the pelvic bone, which is located by the hip. Doctors generally give a type of medication called anesthesia beforehand to numb the area. Anesthesia is medication that blocks the awareness of pain.

  • Lumbar puncture (spinal tap). A lumbar puncture is a procedure in which a needle is used to take a sample of cerebral spinal fluid (CSF) to look for cancer cells or tumor markers. Tumor markers are substances found in higher than normal amounts in the blood, urine, or body tissues of people with certain kinds of cancer. CSF is the fluid that flows around the brain and the spinal cord. Patients are often given an anesthetic to numb the lower back before the procedure or other medications to calm or relax your child (sedation).

  • Ultrasound. An ultrasound uses sound waves to create a picture of the internal organs. Patients are usually awake during an ultrasound.

  • Computed tomography (CT or CAT) scan. A CT scan takes pictures of the inside of the body using x-rays taken from different angles. A computer then combines these pictures into a detailed, 3-dimensional image that shows any abnormalities or tumors. A CT scan can also be used to measure the tumor’s size. Sometimes, a special dye called a contrast medium is given before the scan to provide better detail on the image. This dye can be injected into a patient’s vein or given as a pill or liquid to swallow. When possible, it is best to have this test done in a pediatric specialty center where it can be supervised by pediatric radiologists. These centers are aware of the potential risks of radiation exposure from a CT scan.

  • Magnetic resonance imaging (MRI). An MRI uses magnetic fields, not x-rays, to produce detailed images of the body. MRI can also be used to measure the tumor’s size. A special dye called a contrast medium is given before the scan to create a clearer picture. This dye can be injected into a patient’s vein or given as a pill or liquid to swallow.

  • Positron emission tomography (PET) or PET-CT scan. A PET scan is usually combined with a CT scan (see above), called a PET-CT scan. However, you may hear your doctor refer to this procedure just as a PET scan. A PET scan is a way to create pictures of organs and tissues inside the body. A small amount of a radioactive sugar substance is injected into the patient’s body. This sugar substance is taken up by cells that use the most energy. Because cancer tends to use energy actively, it absorbs more of the radioactive substance. However, the amount of radiation in the substance is too low to be harmful to patients. A scanner then detects this substance to produce images of the inside of the body.

  • Scans or radioisotope studies. In these procedures, a material with a small amount of radioactive substance (called a tracer) is injected into the body and then followed with a special camera or x-ray to see where the material goes. These studies can find abnormalities in the liver, brain, bones, kidneys, and other organs.

Many of these tests may be repeated during and after the child's treatment period to find out how well the treatment is working. Review tips and guidance on how to prepare your child for medical procedures.

After diagnostic tests are done, your child’s doctor will review the results with you. If the diagnosis is cancer, these results also help the doctor categorize or describe the cancer. This is called staging.

Information about the cancer from diagnostic testing will help the doctor recommend a specific treatment plan. The next section in this guide is Types of Treatment. Use the menu to choose a different section to read in this guide.