Types of Brain Cancer
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Types of Primary Brain Tumors
Primary brain tumors are tumors that form from cells within the brain. The tumors are categorized by the type of cell in which it first develops.
There are over 120 different types of brain tumors (National Brain Tumor Society). The most common primary brain tumors are called gliomas, which originate in the glial (supportive) tissue. About one third of all primary brain tumors and other nervous system tumors form from glial cells.
There are a number of different types of gliomas, including the following:
- Astrocytomas develop from small, star-shaped cells called astrocytes, and may arise anywhere in the brain or spinal cord. Astrocytomas are the most common primary CNS tumor. In adults, astrocytomas most often occur in the cerebrum, which is the largest part of the brain. The cerebrum uses sensory information to tell us what’s going on around us and how our body should respond. The left hemisphere controls the muscles on the right side of the body, while the right hemisphere controls the muscles on the left. The cerebrum also controls speech, movement, and emotions, as well as reading, thinking and learning.
- Grade I: Pilocytic astrocytoma
- Grade II: Diffuse astrocytoma / Low-grade astrocytoma
- Grade III: Anaplastic astrocytoma
- Grade IV: Glioblastomas (also called glioblastoma multiforme, GBM, or grade IV astrocytoma). Anaplastic astrocytomas and glioblastomas are malignant astrocytomas that grow and spread aggressively, accounting for more than 50 percent of all astrocytomas. Glioblastomas occur most often in adults between the ages of 50 and 70.
- Brain stem gliomas arise in the brain stem, which controls many vital functions, such as body temperature, blood pressure, breathing, hunger, and thirst. The brain stem also serves to transmit all the signals to the body from the brain. The brain stem is in the lowest part of the brain, and connects the brain and spinal cord. Tumors in this area can be difficult to treat. Most brain stem gliomas are high-grade astrocytomas.
- Ependymomas usually occur in the lining of the ventricles, or spaces in the brain and around the spinal cord. Although ependymomas can develop at any age, these brain cancer tumors most commonly arise in children and adolescents. Ependymomas are also a common spinal cord tumor.
- Oligodendrogliomas develop in the cells that produce myelin, the fatty covering that protects nerves in the brain and spinal cord. These tumors are very rare, and usually occur in the cerebrum. They are slow growing and generally do not spread into surrounding brain tissue. These brain tumors occur most often in middle-aged adults. They generally carry a more favorable prognosis as compared to astrocytomas.
- Mixed gliomas have two types of tumor cells: oligodendrocytes and astrocytes. This type of brain tumor most often forms in the cerebrum.
Other Brain Tumors
There are other types of brain tumors that do not begin in glial tissue, including the following:
- Meningiomas (also called meningeal tumors) grow from the meninges, which are the three thin membranes that surround the brain and spinal cord. These tumors are usually benign (non-cancerous). Because these tumors tend to grow very slowly, the brain may be able to adjust to their presence. Meningiomas frequently grow quite large before they cause symptoms. This type of brain cancer occurs most often in women ages 30 to 50.
- Pituitary tumors develop from the pituitary gland. Most pituitary tumors are benign. They are divided by size into macroadenomas (greater than 1 cm in size) and microadenomas (less than 1 cm in size). Arising from the pituitary gland (master gland of the body), these tumors can over-produce a variety of hormones. This overproduction of hormones typically causes symptoms, such as fatigue, menstrual irregularities, and weight gain or loss, among many others. Most pituitary tumors, however, do not produce hormones. These tumors, which are common among 30-50 year olds, can still create problems when they become large enough to push on the nearby optic nerves.
- Craniopharyngiomas develop in the area of the brain near the pituitary gland (the main endocrine gland which produces hormones that control other glands and many body functions, especially growth) near the hypothalamus. These brain tumors are usually benign. However, they may sometimes be considered malignant because they may create pressure on, or damage, the hypothalamus and affect vital functions (such as body temperature, hunger and thirst). These tumors occur most often in children and adolescents, or adults over age 50.
- Germ cell tumors arise from developing sex (egg or sperm) cells, also known as germ cells. The most common type of germ cell tumor in the brain is the germinoma. Aside from the brain, germinomas can form in the ovaries, testicles, chest, and abdomen. Most germ cell tumors occur in children.
- Pineal region tumors occur in or around the pineal gland, a small organ located in the center of the brain. The pineal gland produces melatonin, a hormone that plays an important role in the sleep-wake cycle. These brain cancer tumors can be slow growing (pineocytoma) or fast growing (pineoblastoma). Since the pineal region is very difficult to reach, it requires a high level of surgical expertise to remove these tumors.
- Medulloblastomas are fast-growing brain tumors that develop from the neurons of the cerebellum. The cerebellum is the lower back of the brain and controls movement, balance and posture. These tumors are usually found in children or young adults.
- Primary CNS lymphomas develop in lymph tissue of the brain or spinal cord. This type of brain tumor is usually found in people whose immune systems are compromised.
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