Astrocytomas—American Cancer Society

There are many types of brain tumors.

Glioma is a general term for tumors that start in glial cells. A number of tumors can be considered gliomas, including:

• Astrocytomas (which include glioblastomas)
• Oligodendrogliomas
• Ependymomas

About 3 out of 10 of all brain tumors are gliomas. Most fast-growing brain tumors are gliomas.

Astrocytomas are tumors that start in glial cells called astrocytes. About 2 out of 10 brain tumors are astrocytomas.

Most astrocytomas can spread widely throughout the brain and blend with the normal brain tissue, which can make them very hard to remove with surgery. Sometimes they spread along the cerebrospinal fluid (CSF) pathways. It is very rare for them to spread outside of the brain or spinal cord.

Astrocytomas (like other brain tumors) are classified into 4 grades.

• Non-infiltrating (grade I) astrocytomas do not usually grow into nearby tissues and tend to have a good prognosis. These include pilocytic astrocytomas and subependymal giant cell astrocytomas (SEGAs). They are more common in children than in adults.
• Low-grade (grade II) astrocytomas, such as diffuse astrocytomas, tend to be slow growing, but they can grow into nearby areas and can become more aggressive and fast growing over time.
• Anaplastic (grade III) astrocytomas grow more quickly.
• Glioblastomas (grade IV) are the fastest growing. These tumors make up more than half of all gliomas and are the most common malignant brain tumors in adults.

https://www.cancer.org/cancer/brain-spinal-cord-tumors-adults/about/types-of-brain-tumors.html