Neuro-Oncology University of Washington Medical Center

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About Brain Tumors: Types of Brain Tumors A glioma is a tumor involving the supportive cells (or glial cells), found in the white matter of the brain. There are three main types of glial cells - the astrocytes, the oligodendrocytes, and the ependymal cells. Tumors originating from these cells are called astrocytomas, oligodendrogliomas, and ependymomas. Tumors other than gliomas also can occur in other brain structures. Some of the more common areas involved include the meninges (tissue coverings of the brain), the pituitary gland, and the cranial nerves. Benign and Malignant Tumors Tumors of the nervous system can be benign or malignant. These determinations are based on how the tumor cells look under the microscope, their potential for growth, and their potential rate of growth. Generally, benign tumors are tumors that if removed completely do not recur, or recur very slowly. Malignant tumors tend to recur. Any tumor, benign or malignant, that is not completely removed will recur or to continue to grow. If the tumor is malignant, it has the potential to recur at a more rapid rate than benign tumors. Tumors that are "inoperable" because they are located in a critical area of the brain, may be described as malignant by location. These tumors are considered to be malignant because the tumor may continue to grow unless it can be eradicated by radiation therapy or chemotherapy. Astrocytomas and Oligodendrogliomas Astrocytomas and oligodendrogliomas are tumors that have "finger-like" extensions into the brain substance. This feature makes it very difficult to remove the entire tumor. The surgeon may remove all the tumor that is visible but there may still be microscopic tumor cells remaining. This means that these tumors can recur - at a slow rate for benign, low-grade, tumors and a faster rate for malignant, high-grade, tumors. This is why further treatment after surgery is often recommended with radiation therapy and/or chemotherapy. Chemotherapy is generally reserved for malignant tumors or for tumors which have recurred. Astrocytomas are graded according to how benign or malignant they appear under the microscope. Grades 1 and 2 astrocytoma (low-grades) are considered "benign" and are slow-growing. Both grades 3 and 4 (high-grades) astrocytomas are malignant. A grade 3 astrocytoma is called an anaplastic astrocytoma; a grade 4 astrocytoma is more malignant and faster growing than a grade 3, and is called a glioblastoma multiforme. For more information regarding brain tumor classification, see the booklet "Brain Tumors, a Guide" from the National Brain Tumor Foundation.   Top of Page   |  Next Page