How pediatric brain and spinal cord tumors are diagnosed

Diagnosis is the process of finding out which disease is observed symptoms. Only after this is done can doctors determine the best treatment plan. In many cases, diagnosing a brain tumor can be challenging because the early symptoms can mimic those of other, less serious conditions. However, once a diagnosis of a brain tumor is considered, an imaging evaluation of the brain is required to confirm the suspicion. Following examination and evaluation of signs and symptoms, MRI and CT scans are useful in determining the presence of a brain or spinal cord tumor, but a biopsy is the only reliable way to confirm a specific diagnosis.

Diagnostic tools

MRI (magnetic resonance imaging) scans combine high-frequency radio waves and a strong magnetic field to produce a picture of the inside of the brain. No X-ray radiation is involved.
CT (computerized tomography) scans use a sophisticated X-ray machine combined with a computer to create a picture of the inside of the brain.
PET (positive emission tomography) scans provide a picture of brain activity. They may be used when trying to tell whether a CT or MRI scan is showing the return of a tumor or damaged tissue caused by radiation. A PET scan may be used in addition to a CT or MRI.
SPECT (Single Photon Emission Computed Tomography) provides information similar to the PET scan, but is more widely available.
A biopsy is a procedure in which a sample of tumor tissue is removed so that doctors can study its characteristics. The sample can be taken through an open or surgical biopsy, or a needle biopsy. If the tumor is difficult or impossible to resect (remove) safely, a doctor may perform a needle biopsy to identify the type of tumor and determine what treatment would be most useful. If the tumor is surgically resectable, tissue removed during the resection process should be examined by a neuropathologist to confirm the diagnosis.

What's the difference between a benign tumor and a malignant tumor?

Brain and spinal cord tumors are also referred to as tumors of the central nervous system (CNS). CNS tumors are classified as "benign" or "malignant" based on the appearance of their cells under a microscope. In general, benign tumors are grow slowly and do not spread to areas of the CNS that are distant from their initial site of origin. In some cases, they also have well-defined borders that help in their removal. However, when located in vital areas of the brain or spinal cord, a benign tumor can be life-threatening.

A malignant tumor, also called "cancer," is always a threat to life. Malignant tumors invade and destroy healthy tissue. They usually grow rapidly, and can send "roots" into normal tissue. Individual cells from malignant CNS tumors sometimes break free from the mass and travel to other parts of the CNS.

There are many pediatric tumor types. Their name or classification is based on the tumor's cell structure, composition, the location of the tumor, and the function of the tissue involved. Tumors are also "graded," with Grade I tumors considered benign (non-cancerous). Grade IIs are a significant step higher, with cells that become malignant more easily. Grade III and IV tumors are malignant with increased severity. The more aggressive and dangerous the tumor, the higher the grade. Assigning a grade helps doctors communicate clearly about the tumor.

Staging is another way to categorize a CNS tumor. The "stage" of the cancerous tumor is based on its size and the extent to which it has spread beyond the site of its origin. Staging is very useful for some childhood brain tumors, especially medulloblastoma and primitive neuroectodermal tumors (PNET). For others, including benign tumors, its usefulness is limited.

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Additional resources

Click here for more information on the diagnosis of childhood brain tumors.