(AS-troh-sy-TOH-muh) 
A type of glioma that forms in star-shaped cells called astrocytes in the brain and spinal cord. Astrocytomas may be benign (not cancer) or malignant (cancer). They are grouped based on their grade, which is determined by how abnormal the tumor cells look under a microscope and how quickly the tumor is likely to grow, spread, and come back after treatment. Low-grade astrocytomas, such as pilocytic astrocytomas, tend to grow slowly and are more common in children. High-grade astrocytomas, such as glioblastoma, tend to grow and spread within the brain and spinal cord quickly and are more common in adults.
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Figure
Anatomy of the brain showing the cerebrum, ventricles (with cerebrospinal fluid shown in blue), cerebellum, brain stem (pons and medulla), and other parts of the brain.