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, astrocytoma. They also do tests to learn if the 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 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 is not possible, the doctor may suggest other tests that will help make a diagnosis.

How astrocytoma is diagnosed

There are many tests used for diagnosing astrocytoma. Not all tests described here will be used for every person. 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 astrocytoma:

• 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 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 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.

• Biopsy. Other tests can suggest that a tumor is present, but only a biopsy can make a definite diagnosis. For astrocytoma, a biopsy is done to determine the type and grade of the tumor. It can also be used to identify certain molecular features that help the doctor plan treatment (see below). During a biopsy, a doctor called a neurosurgeon will remove a small piece of tissue from the tumor. A neurosurgeon specializes in treating a CNS tumor using surgery. A pathologist then analyzes the sample. A pathologist is a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease.

• Biomarker testing of the tumor. Your child's doctor may recommend running laboratory tests on a tumor sample 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 can help determine your child’s treatment options (see Types of Treatment).

After diagnostic tests are done, your child’s doctor will review the results with you. If the diagnosis is astrocytoma, 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 astrocytoma. Use the menu to choose a different section to read in this guide.