This "Grade-4" astrocytoma has a clear demarcation or margin that separates the major area of tumorous cells from the remaining brain tissue. However, all astrocytomas involve some infiltration into surrounding tissue. This results in recurrence of the tumor after surgical decompression and resection.

Astrocytoma: Normal astrocytes exist as a fibrous type within the white matter of the brain and a protoplasmic variety residing in the gray matter. Both are involved in metabolism and general function of neurons. They are also involved in maintaining the blood-brain barrier. A group of these cells may proliferate and transform into a malignant tumor. This malignant transformation may be graded according to the categories outlined in the introduction.