Medulloblastoma - Childhood: Diagnosis

Approved by the Cancer.Net Editorial Board, 02/0219

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. They also do tests to learn if a cancerous tumor has spread to another part of the body from where it started. If this happens, it is called metastasis. For example, imaging tests can show if the tumor has spread. Imaging tests show pictures of the inside of the body. Doctors may also do tests to learn which treatments could work best.

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

This section describes options for diagnosing medulloblastoma. Not all tests listed below will be used for every child. Your child’s doctor may consider these factors when choosing a diagnostic test:

  • 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 medulloblastoma:

  • Biopsy. A biopsy is the removal of a small amount of tissue for examination under a microscope. Other tests can suggest that a tumor is present, but looking at the tumor tissue removed during a biopsy, sometimes using surgery (see below), is the only way to make a definite diagnosis. A pathologist then analyzes the sample(s). A pathologist is a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease.

  • Surgical removal of the tumor. During surgery, a neurosurgeon removes as much of the tumor as possible (see the Types of Treatment section). A neurosurgeon is a doctor who specializes in removing a tumor from the brain or spine with surgery. A sample of the removed tissue is then examined under a microscope by a pathologist for a biopsy (see above).

  • 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.

  • Magnetic resonance imaging (MRI). An MRI uses magnetic fields, not x-rays, to produce detailed images of the body. MRI can 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.

  • 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, blood, 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. The child is given an anesthetic that numbs the lower back before the procedure. For people with medulloblastoma, doctors usually perform a lumbar puncture after the tumor is removed through surgery (see the Types of Treatment section).

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

The next section in this guide is Stages. 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.