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This is the most common primary CNS tumor, composed of neoplastic astrocytes (non-neoplastic astrocytes are a normal type of brain cell). These are usually located in the cerebral hemispheres. Astrocytomas come in 4 grades of biological aggressiveness (1-4); grade 3 tumors are often called anaplastic astrocytomas and grade 4 tumors glioblastomas. Thus, astrocytoma usually refers to a grade 1 or grade 2 tumor. Grade 2 tumors are often called "low-grade astrocytomas." Such tumors are characterized by slow growth, cyst formation and invasion of surrounding area. they have the capacity to develop into a more malignant type of astrocytoma.
Anaplastic Astrocytoma
This is a type of intermediate-grade astrocytoma most common in middle-aged people. It is sometimes called a grade 3 astrocytoma. | 
