Brain Tumors

Brain tumors are categorized as primary or secondary. Primary brain tumors start in the brain and may be either benign or malignant. About 190,000 Americans are diagnosed each year with a primary brain tumor.  Children usually have primary tumors. This is the leading cause of solid tumor deaths in children under the age 20 and is the third leading cause of cancer death in young adults ages 20-39.

Secondary brain tumors are malignant and are more common.  About 90,000 cases are diagnosed each year in the United States. Secondary tumors result from cancer that started elsewhere and metastasized to the brain. Adults usually have secondary tumors which have spread there from the lung, breast, or other parts of the body. This is not considered brain cancer.  This occurs in 10-15% of cancer patients.

Many brain tumors can be treated successfully with either surgery, radiation therapy, chemotherapy or a combination of any of these.  Brain tumor patients have poorer survival rates than many other types of cancer patients.  This includes certain benign brain tumors.

A brain tumor that develops from glial cells is called a glioma. Glial cells often surround the neurons in the nervous system.  The neurons send signals to and from the nerves.  Glial cells protect and support the neurons.  About half of all primary brain tumors and one-fifth of all primary spinal cord tumors form from glial cells. Gliomas tend to grow in the brain, but may also grow in the brain stem, optic nerves, spinal cord, or cerebellum.  Gliomas are divided into subgroups depending on the origin of the glial cells.

The most common type of glioma is an astrocytoma which develops from star-shaped glial cells that support nerve cells. These tumors can be found anywhere in the brain, but the frontal lobe is the most common. Astrocytomas are the most common primary tumor found in the central nervous system.

Chordomas are most common in young adults in their 20s and 30s.  They develop from leftover remnants of the flexible spine-like structure that forms and dissolves early in fetal development, but is later replaced by the spinal cord. These tumors are usually slow-growing, but they can metastasize or recur after treatment. The usual treatment is a combination of surgery and radiation therapy.

Craniopharyngiomas grow in the area of the optic nerves and the hypothalamus. Like chordomas, they grow from cells that remain from early fetal development. Craniopharyngiomas cause problems with vision and hormones.  They slow children's growth and cause poor regulation of their water balance. Benign craniopharyngiomas usually affect infants and children, but can occur in adults. They can be removed with minimal or no brain damage in many cases because of the precise instruments and techniques now available.  If the tumor continues to grow and cannot be removed surgically, radiation therapy may also be required.

Medulloblastomas are the most common primitive neuroectodermal tumor (PNET), representing more than 25% of all childhood brain tumors. They occur in children more often than in adults. Medulloblastoma most often arises in the cerebellum, located in the lower back part of the brain and causes symptoms that include headache, nausea, vomiting and problems with muscle coordination (ataxia). Unlike other primary brain tumors, medulloblastoma has a tendency to spread throughout the nervous system if it remains untreated. In unusual cases, medulloblastomas may spread outside the nervous system, to the lymph nodes, bone marrow, lungs or other parts of the body. In many cases, they are treated with surgery and radiation therapy alone. They are fast-growing tumors, but because they are very sensitive to radiation therapy and chemotherapy they can often be treated effectively.

Most brain tumours are named after the type of cells from which they develop. Medulloblastomas are malignant tumours formed from poorly developed cells at a very early stage of their life. They develop in the cerebellum (see diagram below), in a part of the brain called the posterior fossa, but may spread to other parts of the brain. Very rarely they may spread to other parts of the body. If they do spread to other parts of the brain or to the spinal cord, this is usually through the cerebrospinal fluid (CSF). CSF is the fluid around the brain and the spinal cord.

Medulloblastomas usually occur in children, particularly between the ages of three and eight. They make up about 20% of all childhood brain tumours. The tumour is more common in males than females. They can also occur in adults but this is extremely rare. 

Meningioma

A meningioma is a common brain tumor that originates from the meninges, the thin membranes or lining that cover the brain and spinal cord. As they grow, meningiomas compress adjacent brain tissue. Meningioma symptoms are often related to this compression of brain tissue, which can also affect cranial nerves and blood vessels. In some cases, meningioma growth can also extend into the bones of the head and face, which may produce visible changes. Meningiomas account for about 27% of all primary brain tumors and tend to affect more women than men. Most meningiomas are considered benign tumors. However, unlike benign tumors elsewhere in the body, benign brain tumors can sometimes cause disability and may sometimes be life threatening. In many cases meningiomas appear to grow slowly. Other meningiomas grow more rapidly or have sudden growth spurts. There is no way to predict the rate of growth of a meningioma or to know for certain how long a specific tumor was growing before diagnosis. Although most people develop a single meningioma, it is also possible to have several tumors growing simultaneously in different parts of the brain and spinal cord. Because recurrent tumors cannot be predicted, it is very important for meningioma survivors to receive regular follow up scans as part of their lifetime health care in order to avoid critical care being neglected.

Pineal Tumors

These tumors arise in the region of the pineal gland, a small structure deep within the brain. They account for about 1% of brain tumors, but make up 3% to 8% of the intracranial tumors that occur in children. At least 17 different types of tumors may occur in this area, many of which are benign. The three most common types of pineal region tumors are gliomas, germ cell tumors and pineal cell tumors. Surgery is absolutely necessary to obtain a sample of tumor tissue so the pathologist can confirm a precise histological diagnosis, which is essential in planning the appropriate therapy. Benign pineal tumors can be removed surgically. The germinoma, the most common malignant tumor in this area, can be cured in more than 90% of patients. Other malignant germ cell tumors occurring in this region are treated with chemotherapy followed by radiation therapy. Over the past 5 years, the prognosis for children with pineal tumors has improved dramatically.

Pituitary Adenoma

The pituitary gland is a small oval structure located at the base of the brain in the center of the head, behind the eyes and optic nerve. It is about the size of a pea but is very important because it secretes several chemical messengers known as hormones, which help control the body's other glands and regulate growth, metabolism, maturation and other essential body processes. A tiny tumor located just next to the gland, pituitary adenomas account for about 10% of brain tumors. Doctors classify pituitary tumors into two groups - secreting and nonsecreting. Secreting tumors release unusually high levels of pituitary hormones, triggering a constellation of symptoms. They are usually much smaller than the gland when they begin to cause symptoms and the symptoms depend on the tumor's size and the kind of hormone the tumor secretes. Prolactin-secreting adenomas affect sexual characteristics and cause impotence in men. Adenomas secreting growth hormone cause acromegaly (abnormal body growth, enlarged facial features, hands and feet) and gigantism (excessive size and stature). The less common adrenocorticotropic hormone-secreting adenoma causes Cushing's disease. Some adenomas secrete a combination of these or other hormones and some secrete none. Almost all adenomas are benign, but their slow expansion compresses normal structures that surround it, suppressing normal pituitary function and sometimes causing headaches or problems with vision. Pituitary adenomas rarely metastasize or spread to other areas of the body. They are removed in an operation using microsurgical techniques, a very successful form of treatment for the majority of patients.

Primitive Neuroectodermal Tumors

Primitive Neuroectodermal Tumors (PNETs) usually affect children and young adults. Their name reflects the belief, held by many scientists, that these tumors spring from primitive cells left over from early development of the nervous system. PNETs are usually very malignant, growing rapidly and spreading easily within the brain and spinal cord. In rare cases, they cause cancer outside the central nervous system. Medulloblastomas are the most common PNET. Other more rare PNETs include neuroblastomas, pineoblastomas, medulloepitheliomas, ependymoblastomas and polar spongioblastomas. Because their malignant cells often spread in a scattered, patchy pattern, PNETs are difficult to remove totally through surgery. Doctors usually remove as much tumor as possible with surgery then prescribe high doses of radiation and, in some cases, chemotherapy.

Schwannoma

Schwannomas arise from the cells that form a protective sheath around the body's nerve fibers. They are usually benign and are surgically removed when possible. One of the more common forms of schwannoma affects the eighth cranial nerve, which contains nerve cells important for balance and hearing. Also known as vestibular schwannomas or acoustic neuromas, these tumors may grow on one or both sides of the brain.

Vascular Tumors