Astrocytoma at 20x Magnification
Astrocytomas are the most common variety of glioma (tumor that arises from glial cells) and may be benign or malignant. Like all brain tumors, astrocytomas are very serious and are usually described by the medical community based upon their grade. The grade of a tumor can generally be determined by observing the tumor cells under a microscope. High-grade tumors are characterized by a greater presence of abnormal cells and more rapid cell growth than low-grade tumors. The brisk pace of high-grade tumor cell growth allows these tumors to quickly invade the central nervous system, making them much more difficult to treat than low-grade brain tumors. In children, the majority of astrocytomas that occur are classified as low-grade, but in adults most of the tumors are of the high-grade variety. The most advanced astrocytomas (grade IV) are usually described as glioblastoma multiforme.