Diagnosis

Doctors use many tests to diagnose a tumor and determine if it has metastasized (spread). Some tests may also determine which treatments may be the most effective. For most types of tumors, a biopsy is the only way to make a definitive diagnosis of cancer. If a biopsy is not possible, the doctor may suggest other tests that will help make a diagnosis. Imaging tests may be used to find out whether the tumor has metastasized. Your doctor may consider these factors when choosing a diagnostic test:

• Age and medical condition
  
  
• The type of tumor suspected
  
  
• Severity of symptoms
  
  
• Previous test results

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 cancer is present, but only a biopsy can make a definite diagnosis. The sample removed during the biopsy is analyzed by a pathologist (a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease).

Computed tomography (CT or CAT) scan. A CT scan creates a three-dimensional picture of the inside of the body with an x-ray machine. A computer then combines these images into a detailed, cross-sectional view that shows any abnormalities or tumors. Sometimes, a contrast medium (a special dye) is injected into a vein to provide better detail.

Magnetic resonance imaging (MRI). An MRI uses magnetic fields, not x-rays, to produce detailed images of the body. A contrast medium may be injected into a patient’s vein to create a clearer picture.

Lumbar puncture (spinal tap). A lumbar puncture is a procedure in which a doctor takes a sample of cerebral spinal fluid (CSF) to look for cancer cells, blood, or tumor markers (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. Doctors generally give an anesthetic to numb the lower back before the procedure.

Learn more about what to expect when having common tests, procedures, and scans.

Find out more about common terms used during a diagnosis of cancer.