After the childhood cerebellar astrocytoma has been removed, tests are done to find out if there is tumor remaining. The extent or spread of cancer is usually described as stages. For childhood cerebellar astrocytoma, the grade of the tumor is used instead of stages. The grade of the tumor refers to how abnormal the cancer cells look under a microscope and how quickly the tumor is likely to grow and spread. It is important to know the grade of the tumor and if there were any cancer cells remaining after surgery in order to plan treatment.

There are two grades for childhood cerebellar astrocytoma:

• Grade I pilocytic tumors are very slow-growing and rarely spread. These tumors form inside cysts.
• Grade II diffuse or fibrillary tumors spread slowly within the brain.

The following procedure may be used to determine if any cancer cells remain in the brain after surgery:

• MRI (magnetic resonance imaging): A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the brain and spinal cord. A substance called gadolinium is injected into the patient through a vein. The gadolinium collects around the cancer cells so they show up brighter in the picture. This procedure is also called nuclear magnetic resonance imaging (NMRI).

Cerebellar astrocytomas do not usually spread from the cerebellum to other parts of the brain or body.