Primary Brain Tumors

Primary brain tumors originate from brain cells; whereas, secondary or metastatic tumors arise in other organs and spread to the brain through the bloodstream. The most common primary brain tumors are called gliomas.

These tumors arise from glial cells, which are the supporting cells of the central nervous system. In contrast, neurons or nerve cells of the brain rarely give rise to tumors. There are three main types of gliomas: astrocytomas, oligodendrogliomas and ependymomas.

Astrocytoma

These tumors arise from star-shaped brain cells called astrocytes. (VISIT LINK)
Astrocytomas can arise anywhere in the brain, but in adults they usually arise in the largest part of the brain known as the cerebrum. In children, they develop in the cerebellum, brain stem, and cerebrum. Astrocytomas are graded from I to IV with the least aggressive designated grade I and the most aggressive, or rapidly growing, designated grade IV. Grades I and II astrocytomas are called low grade astrocytoma.

Grade III astrocytomas are sometimes also called anaplastic astrocytomas (pictured at right) and grade IV astrocytomas are usually referred to as glioblastoma multiforme or GBM.

Glioblastoma multiforme

Glioblastoma (pictured right) is the most common and one of the most aggressive primary brain tumors. It can arise from changes in the growth pattern of either a low grade astrocytoma or an anaplastic astrocytoma. Alternatively, GBM may arise de novo without any prior history of a lower grade primary brain tumor. Because of its aggressive nature, treatment of glioblastoma usually involves a combination of surgery, radiation therapy and chemotherapy.

Brain stem glioma

This type of tumor (pictured left) is usually an astrocytoma that is distinguished by the specific brain location in which it arises. Brain stem gliomas are most frequently diagnosed in young children and in middle-aged adults.

They can produce serious neurologic symptoms due to their location in close proximity to critical brain structures. Treatment usually involves a combination of radiation therapy and chemotherapy. Surgical treatment is possible only rarely.

Ependymoma

This tumor (pictured right) arises from cells that line the ventricles, which are the fluid-filled spaces within the brain, or from the central canal of the spinal cord. They more commonly occur in children and young adults and can develop either in the ventricles or within the substance of the brain.

Oligodendroglioma

This is a type of glioma (pictured below) arises from cells that produce a fatty substance called myelin that covers the nerves like electrical insulation. These tumors usually occur in the cerebrum. They may grow slowly and tend not to spread into the surrounding brain tissue as extensively as astrocytomas do. They are most common in young and middle-aged adults. Oligodendrogliomas can be graded much like astrocytomas.

Anaplastic oligodendrogliomas are of a higher grade than low grade oligodendrogliomas and are more aggressive. Chemotherapy treatment is particularly effective for some anaplastic oligodendrogliomas. Some gliomas contain a mixture of cells that look like oligodengrogliomas and other cells that look like astrocytomas. Such tumors are called mixed gliomas or oligoastrocytomas. Mixed gliomas tend to behave more like astrocytomas than like oligodendrogliomas.

Other Gliomas

There are other specific types of gliomas with their own individual characteristics and modes of growth. They include: juvenile pilocytic astrocytoma, subependymal giant cell astrocytoma, ganglioglioma, subependymoma and pleomorphic xanthoastrocytoma or PXA.

Some types of primary brain tumors do not arise from glial cells. The most common of these are:

Meningioma

This common tumor (pictured right) arises from the meninges which are the protective coverings of the brain located between the skull and the brain itself. Meningiomas are usually benign, although they can occasionally be malignant. They usually press on the brain, but do not invade it. Meningiomas may grow slowly and can reach a very large size, given sufficient time. Treatment is usually surgical, although radiation therapy and gamma knife (radiosurgery) can be of help for certain meningiomas.

Schwannoma

This is a tumor that arises from the Schwann cell. These cells are present in nerves, including those that control balance and hearing. One common site of schwannoma growth is on the vestibular nerve, which carries signals from the inner ear to the brain stem. Tumors arising in this location are called acoustic neuroma (AN), although a more correct name is vestibular schwannoma (VS). These tumors occur most often in adults and produce progressive hearing loss in one ear. Some patients with a genetic condition called neurofibromatosis or NF have vestibular schwannomas on both sides (see picture). Patients with this genetic disorder may have schwannomas in other locations and can develop meningiomas as well.

Metastatic Brain Tumors

Cancer (pictured right) can spread from its site of origin through the bloodstream to another part of the body. It can lodge in other organs and grow in these sites. The new tumors have the same kind of abnormal cells as the primary tumor. Cancer that spreads to the brain from another part of the body is quite different from a primary glioma. When cancer cells spread to the brain from another organ, such as the lung, breast, skin, kidney or colon, physicians call the brain tumor a metastatic or secondary brain tumor. Metastatic tumors of the brain are much more common than primary brain tumors. Treatment can take the form of surgery, radiation therapy, gamma knife (radiosurgery), and in some cases chemotherapy.

Craniopharyngioma

This tumor (pictured left) grows at the base of the brain and arises from the band of tissue that connects the brain and the pituitary gland. Craniopharyngiomas occur in both adults and in children and generally consist of solid tumor tissue and a fluid-filled cyst. Treatment usually involves microneurosurgery; however, radiation therapy and gamma knife (radiosurgery) may be used in some cases as well.

Pituitary Adenoma

These are common tumors that arise from the pituitary gland located at the base of the brain. If they grow large enough, they can compress the optic nerves causing serious vision problems. Such tumors are called macroadenomas (pictured right) . Smaller tumors are known as microadenomas. Some pituitary tumors produce excessive amounts of hormones that can disrupt the bodyﾒs metabolism. Pituitary tumors compress the normal pituitary gland and can adversely affect its function. Some pituitary tumors can be treated medically with drugs like bromocryptine and octreotide. Others must be treated surgically. For some patients, conventional radiation therapy and gamma knife (radiosurgery) can be used effectively as well.