Condition: Astrocytoma

An astrocytoma is a tumor that arises from the star-shaped cells (astrocytes) that form the supportive tissue of the brain. Other supportive cells of the brain include oligodendrocytes and ependymal cells. Collectively, these cells are known as glial cells and the tissue they form is known as glial tissue. Tumors that arise from the glial tissue, including astrocytomas, are collectively referred to as gliomas.

The World Health Organization (WHO) classifies astrocytomas into four grades depending on how fast they are growing and the likelihood that they will spread (infiltrate) to nearby brain tissue. Noninfiltrating astrocytomas usually grow more slowly than the infiltrating forms. Infiltrating, or diffuse astrocytomas are more common than noninfiltrating astrocytomas. They are generally more common in men and are most common in the cerebral hemispheres of adult patients. In children they occur both in the cerebral hemispheres as well as the brain stem. Tumors from oligodendrocytes (oligodendrodendrogliomas) are also in the category of infiltrating gliomas and can occasionally be difficult to distinguish from astrocytomas. Some infiltrating gliomas are categorized as mixed oligodendroglioma-astrocytoma (oligoastrocytoma).

Grade I astrocytoma is usually a noninfiltrating tumor. The most common type of grade I astrocytoma is pilocytic astrocytoma which is also known as juvenile pilocytic astrocytoma or JPA. This tumor grows slowly but can become very large. Pilocytic astrocytoma occurs most often in the cerebellum, cerebrum, optic nerve pathway and brainstem. This tumor occurs most often in children and teens and accounts for 2% of all brain tumors.

Grade II astrocytoma is also called low-grade astrocytoma or diffuse astrocytoma and is usually an infiltrating tumor. This tumor grows relatively slowly and usually does not have well-defined borders. It occurs most often in adults between the ages of 20 and 40.

Grade III astrocytoma is also called anaplastic (malignant) astrocytoma because this tumor grows more quickly than a grade II astrocytoma. Anaplastic astrocytoma occurs most often in adults between the ages of 30 and 50, and accounts for 4% of all brain tumors.

Grade IV astrocytoma is also called glioblastoma or GBM and is the most aggressive type of nervous system tumor. It is also referred to as glioblastoma multiforme because of its wide variety of appearances under the microscope. Rarely, non-glial tissue elements can exist in a glioblastoma. The most common variant of GBM showing these additional tissue elements is called a mixed glioblastoma-sarcoma, or gliosarcoma. GBM occurs most often in adults between the ages of 50 and 80, is more common in men, and accounts for 23% of all primary brain tumors.