Central Nervous System Tumors (Brain and Spinal Cord) - Childhood: Diagnosis

Approved by the Cancer.Net Editorial Board, 09/2023

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, a tumor in a child's central nervous system (CNS). They also do tests to learn if a tumor has spread to another part of the body from where it started. If a tumor has spread, it is called metastasis. Doctors may also do tests to learn which treatments could work best.

For most tumor types, a biopsy is the only sure way for the doctor to know if an area of the body has a tumor and learn its type. In a biopsy, the doctor takes a small sample of 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 a CNS tumor is diagnosed

There are different tests used for diagnosing a CNS tumor. Not all tests described here will be used for every child. Your child’s doctor may consider these factors when choosing a diagnostic test:

  • The type of tumor suspected

  • Your child’s signs and symptoms

  • Your child’s age and general health

  • The results of earlier medical tests

In addition to a physical examination, the following tests may be used to diagnose a CNS tumor:

  • Magnetic resonance imaging (MRI). This is the primary test used to find a brain tumor and plan treatment. An MRI produces detailed images of the inside of the body using magnetic fields, not x-rays. 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.

  • 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 combines these pictures into a detailed, 3-dimensional image that shows any abnormalities or tumors. A CT scan can 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. Although MRI (see above) is the preferred test, a CT scan may be an option for diagnosing a brain tumor.

  • Biopsy. A biopsy is the only way to make a definite diagnosis, even if other tests can suggest a tumor is present. A biopsy for a CNS tumor is usually done using surgery to remove a small amount of tissue for examination under a microscope. A pathologist analyzes the sample(s). A pathologist is a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease. The type of biopsy performed depends on the location of the tumor.

  • Biomarker testing of the tumor. Your doctor may recommend running laboratory tests on a tumor to identify specific genes, proteins, and other factors unique to the tumor. This may also be called molecular testing of the tumor. Results of these tests may help determine your child's treatment options. Biomarker testing is not currently done for all types of childhood CNS tumors, but it may be done for some tumor types and in clinical trials (see Latest Research).

After diagnostic tests are done, your child’s doctor will review the results with you. If the diagnosis is a CNS tumor, these results also help the doctor describe the tumor. This is called staging and grading.

The next section in this guide is Stages and Grades. It explains the system doctors use to describe the extent of the disease. Use the menu to choose a different section to read in this guide.