Primary brain cancer starts within the substance of the brain, spinal cord or nerves. Some tumors which arise from the brain or spine coverings (meninges) are also considered primary brain tumors. Metastatic brain tumors have spread from cancer in other parts of the body, most frequently from the lungs, breast and colon.
The overall lifetime risk of getting a brain tumor is less than 1%.There are many different types of brain tumors, based on what cells are affected and how they appear under a microscope. Tumors can be classified into four general categories:
Gliomas
These tumors occur in the glial cells, which help support and protect critical areas of the brain. Gliomas are the most common type of brain tumor in adults, responsible for about 42% of all adult brain tumors. Gliomas are further characterized by the types of cells they affect:
Astrocytoma: Star-shaped cells that protect neurons. Tumors of these cells can spread from the primary site to other areas of the brain, but rarely spread outside the central nervous system. Astrocytomas are graded from I to IV depending on the speed of progression:
Grade I (pilocytic astrocytoma): Slow growing, with little tendency to infiltrate surrounding brain tissue. Most common in children and adolescents.
Grade II (diffuse astrocytoma): Fairly slow-growing, with some tendency to infiltrate surrounding brain tissue. Mostly seen in young adults.
Grade III (anaplastic/malignant astrocytoma): These tumors grow rather quickly and infiltrate surrounding brain tissue.
Grade IV (glioblastoma multiforme, GBM): An extremely aggressive and lethal form of brain cancer. Unfortunately, it is the most common form of brain tumor in adults, accounting for 67% of all astrocytomas.
Oligodendroglioma: These cells make myelin, a fatty substance that forms a protective sheath around nerve cells. Oligodendrogliomas, which make up 4% of brain tumors, mostly affect people over 45 years of age. Some subtypes of this tumor are particularly sensitive to treatment with radiation therapy and chemotherapy. Half of patients with oligodendrogliomas are still alive after five years.
Ependymoma: These tumors affect ependymal cells, which line the pathways that carry cerebrospinal fluid throughout the brain and spinal cord. Ependymomas are rare and make up 2% of all brain tumors, however they are the most common brain tumor in children. They generally don’t affect healthy brain tissue and don’t spread beyond the ependyma. Although these tumors respond well to surgery, particularly those on the spine, ependymomas cannot always be completely removed. The five-year survival rate for patients over age 45 approaches 70%.
Meningiomas
These tumors affect the meninges, the tissue that forms the protective outer covering of the brain and spine. One-quarter of all brain and spinal tumors are meningiomas, and up to 85% of them are benign. Meningiomas can occur at any age, but the incidence increases significantly in people over age 65. Women are twice as likely as men to have meningiomas. They generally grow very slowly and often don’t produce any symptoms. In fact, many meningiomas are discovered by accident. Meningiomas can be successfully treated with surgery, but some patients, particularly the elderly, may be candidates for watchful waiting to monitor the disease.
Acoustic Neuroma / Schwannomas
Schwann’s cells are found in the sheath that covers nerve cells. Vestibular schwannomas, also known as acoustic neuromas, arise from the 8th cranial nerve, which is responsible for hearing. Specific symptoms of vestibular schwannoma include buzzing or ringing in the ears, one-sided hearing loss and/or balance problems. Schwannomas are typically benign and respond well to surgery.
Medulloblastoma
This a common brain tumor in children, usually diagnosed before the age of 10. Medulloblastoma occurs in the cerebellum, which has a crucial role in coordinating muscular movements. Some experts believe that medulloblastomas arise from fetal cells that remain in the cerebellum after birth. Tumors grow quickly and can invade neighboring portions of the brain, as well as spreading outside the central nervous system. Medulloblastoma is slightly more common in boys.
Depending on the location and size of the tumor, brain cancer and brain tumorsymptoms experienced by each patient may vary. Most of the common symptoms are due to increased intracranial pressure as the growing tumoraffects surrounding structures:
- Frequent headaches (reported by 50% of patients)
- Blurry vision
- Nausea and/or vomiting
- Personality or cognitive changes
Other brain cancer and brain tumor symptoms are site-specific, including seizures, speech impairment, weakness or numbness on one side and problems with coordination, balance or mobility.