Astrocytomas are tumors that arise from astrocytes, which are cells that form the supportive tissue in the brain. These tumors are graded from I to IV, with grade I being slightly abnormal and grade IV being very abnormal in appearance.
Grade I – Cerebellar pilocytic astrocytomas are found in the cerebellum, which is the part of the brain that controls balance. The majority of these tumors are considered to be benign. In most cases, complete surgical removal is the only treatment required. If total removal of the tumor is not possible, radiation and/or chemotherapy is used. The majority of pilocytic astrocytomas occur in infants and children.
Grade II – Astrocytomas are usually located in the hemispheres of the brain. Surgical removal is the main method of treatment, and radiation may be necessary if the tumor is in an area of the brain responsible for speech, understanding or movement, or if the tumor cannot easily be removed. Chemotherapy is also sometimes considered. Astrocytomas are common in persons age 20-45. These astrocytomas make up about 25% of all gliomas and a significant portion of grade II astrocytomas become more aggressive over time, transitioning into grade III and IV astrocytomas.
Grade III – Anaplastic astrocytomas are moderately fast growing and less well-defined astrocytomas. These tumors are malignant and more aggressive, and therefore, treatment is usually more aggressive than that for lower-grade tumors. Anaplastic astrocytomas are dispersed throughout the surrounding tissue of the brain, and their tentacle-like projections make them harder to remove. Treatment usually involves removal of as much of the tumor as possible plus radiation and chemotherapy. Most patients diagnosed with anaplastic astrocytomas are in their forties.
Grade IV – Glioblastoma multiformes contain various cell types, the most common being astrocytes. The majority of these tumors occur in the cerebral hemispheres. Glioblastoma multiforme cells grow quickly, are not well-defined and frequently spread throughout the brain. Surgery may be performed to remove as much of the tumor as possible, but radiation and chemotherapy are often then used to control the growth of the tumor. Glioblastoma multiforme is the most common type of primary malignant brain tumor and average survival, even with aggressive treatment, is less than one year.