The extent or spread of cancer is usually described as stages. There is no standard staging system for brain tumors. Primary brain tumors may spread within the central nervous system (brain and spinal cord), but they rarely spread to other parts of the body. For treatment, brain tumors are classified by the type of cell in which the tumor began, the location of the tumor in the central nervous system, and the grade of the tumor.

Types of adult brain tumors include the following:

BRAIN STEM GLIOMAS

These are tumors that form in the brain stem, the part of the brain connected to the spinal cord. They are often high-grade. Brain stem gliomas that are high-grade or spread widely throughout the brain stem are difficult to treat successfully. To prevent damage to healthy brain tissue, brain stem glioma is usually diagnosed without a biopsy.

(Refer to the PDQ summary on Childhood Brain Stem Glioma Treatment for more information.)

PINEAL ASTROCYTIC TUMOR

Pineal tumors form in or near the pineal gland. The pineal gland is a tiny organ in the brain that produces the hormone melatonin, a substance that helps control our sleeping and waking cycle. There are several kinds of pineal tumors. Pineal astrocytic tumors are astrocytomas that occur in the pineal region and may be any grade.

PILOCYTIC ASTROCYTOMA (GRADE I)

Astrocytomas are tumors that start in brain cells called astrocytes. Pilocytic astrocytomas grow slowly and rarely spread into the tissues around them. These tumors occur most often in children and young adults. They usually can be treated successfully.

DIFFUSE ASTROCYTOMA (GRADE II)

Diffuse astrocytomas grow slowly, but they often spread into nearby tissues. Some of them progress to a higher grade. They occur most often in young adults.

ANAPLASTIC ASTROCYTOMA (GRADE III)

Anaplastic astrocytomas are also called malignant astrocytomas. They grow rapidly and spread into nearby tissues. The tumor cells look different from normal cells. The average age of patients developing anaplastic astrocytomas is 41 years.

GLIOBLASTOMA (GRADE IV)

Glioblastomas are malignant astrocytomas that grow and spread aggressively. The cells look very different from normal cells. Glioblastoma is also called glioblastoma multiforme or grade IV astrocytoma. They occur most often in adults between the ages of 45 and 70 years.

Refer to the following PDQ summaries for more information on astrocytomas:

• Childhood Cerebral Astrocytoma/Malignant Glioma Treatment
• Childhood Cerebellar Astrocytoma Treatment
• Childhood Visual Pathway and Hypothalamic Glioma Treatment

OLIGODENDROGLIAL TUMORS

Oligodendroglial tumors begin in the brain cells called oligodendrocytes, which support and nourish nerve cells. Grades of oligodendroglial tumors include the following:

• OLIGODENDROGLIOMA (GRADE II): Oligodendrogliomas are slow-growing tumors with cells that look very much like normal cells. These tumors occur most often in patients between the ages of 40 and 60 years.
• ANAPLASTIC OLIGODENDROGLIOMA (GRADE III): Anaplastic oligodendrogliomas grow quickly and the cells look very different from normal cells.