A brain tumor is an abnormal mass of tissue in which cells grow and multiply seemingly unchecked by the mechanisms that control normal cells. The two main brain tumor groups are primary and metastatic.
Primary Brain Tumors
Primary brain tumors include those which originate from the tissues of the brain, or the brain’s immediate surroundings. Primary tumors are categorized as glial or non-glial, and benign or malignant.
In general, brain tumors are treated with surgery, radiation, and/or chemotherapy – alone or in various combinations. Although radiation and chemotherapy are more often used for malignant, residual or recurrent tumors, treatment decisions are made on a case-by-case basis, depending on a number of factors. There are risks and side effects associated with each type of therapy.
Gliomas account for 78 percent of malignant brain tumors. They arise from the supporting cells of the brain, called the glia. These cells are subdivided into astrocytes, ependymal cells and ologodendroglial cells (or oligos).
Meningiomas are the most common benign brain tumors comprising 10 to 15 percent of all brain neoplasms. These tumors originate from the meninges, the membrane-like structures that surround the brain and spinal cord and are rarely malignant. Meningiomas may also arise in the spine.
The most common brain tumor after gliomas, meningiomas and schwannomas are pituitary adenomas. The large majority of pituitary adenomas are benign and fairly slow growing. Even malignant pituitary tumors rarely spread to other parts of the body. Adenomas are the most common disease affecting the pituitary. They most often occur in people in their 30s or 40s, but may also be diagnosed in children. Most can be treated with successful outcomes.
An acoustic neuroma is a benign primary brain tumor of the myelin-forming cells of the vestibulocochlear nerve. About 25% of all acoustic neuromas are treated with medical management; periodic monitoring of the patient’s neurological status, and serial imaging studies.
Microsurgery for acoustic neuroma is the only technique that actually removes the tumor. Radiation treatment is commonly used to slow or stop the growth of the tumor and is effective approximately 90% of the time. Most tumors will stabilize in size, and then will shrink slowly. Shrinkage occurs in approximately 1/3 of tumors within a year after treatment. After 4 years, 2/3 of tumors are smaller, and within 10 years, more than 90% have diminished in size.
In the rare cases that radiosurgery does not result in control of the tumor, it can generally be repeated, or the patient may undergo surgery at that time.
Schwannomas are common benign brain tumors in adults. They arise along nerves, comprised of cells that normally provide the “electrical insulation” for the nerve cells. Schwannomas often displace the remainder of the normal nerve instead of invading it. Acoustic neuromas are the most common schwannoma, arising from the eighth cranial nerve, or vestibular-cochlear nerve, which travels from the brain to the ear. Although these tumors are benign, they can cause serious complications if they grow and exert pressure on nerves and eventually on the brain. Schwannomas may also be found in the spine.
Metastatic brain tumors
Metastatic brain tumors are tumors which arise elsewhere in the body (such as the breast or lungs) and migrate to the brain, usually through the bloodstream. Metastatic tumors are considered cancer, and are malignant.
Metastatic tumors to the brain affect nearly one in four patients with cancer, or an estimated 150,000 people a year. In the past, the outcome for patients with these tumors was very poor. Newer sophisticated diagnostic tools and innovative surgical and radiation approaches can now lead to longer survival and a better quality of life, measured in months to years.