Brain tumors are also called intracranial tumors. A brain tumor is an unusual mass of tissue where the cell growth is uncontrollable and unregulated. There are over 150 types of brain tumors but the two main groups are primary and metastatic.
Tumors that come from the brain tissues or immediate surrounding are primary brain tumors. Primary tumors are groups as glial or non glial and benign or malignant.
Metastatic brain tumors come from other areas in the body such as lungs or breast and move to the brain. They can usually move to the brain through the bloodstream. Metastatic tumors are cancerous and malignant.
25% of patients with metastatic tumors to the brain will get cancer. This is around 150,000 people a year. Nearly 40% of people with lung cancer might develop metastatic brain tumors. With better technology people may survive for a couple of years.
TYPES OF BENIGN BRAIN TUMORS
- Chordomas: these tumors grow slowly and are benign. They are most common in 50-60 year olds. They usually are at the base of the skull or the lower portion of the spine. They can be invasive towards nearby bones and add pressure to the neural tissue. These are rare: 0.2% of primary brain tumors
- Craniopharyngiomas: These are usually benign tumors that are hard to remove as they are located near important structures. They typically come from a part of the pituitary gland, which regulates hormones, so patients will usually need hormone replacement therapy
- Gangliocytomas: these rumors are rare. They include neoplastic nerve cells that are very different from one another. This happens most in young adults.
- Glomus jugulare: They are usually benign tumors that locate underneath the base of the skull on top of the jugular vein. This is the most common type of a glomus tumor. These tumors are only 0.6% of neoplasms in the head/neck.
- Meningiomas: this is the most common tumor in the brain. This is a benign tumor that consists of 10-15% of all neoplasms of the brain. They come from the meninges. The meninges is a membrane-like structures surrounding the brain and the spinal cord
- Pineocytomas: These usually come from pineal cells and are benign. They occur mostly in adults. They are usually well defined, not invasive, similar, and grow very slow
- Pituitary adenomas: These are an extremely common brain tumor behind gliomas, meningiomas, and schwannomas. Most of these tumors will be benign and grow slowly. Adenomas are the most frequent disease affecting the pituitary. This can be diagnosed in children but is mostly in younger adults. Most of these tumors can be cured.
- Schwannomas: These are typical brain tumors that occur in adults. They show up along nerves and are made up of cells that typically provide the electrical insulation for nerve cells. Schwannomas do not invade the nerve but instead displace it. The most common type of schwannome appears on the eighth cranial nerve and is called an acoustic neuromas. These tumors can have severe complications that could lead to death if they continue to grow and put pressure on nerves and the brain. These can occur very rarely on the spine or on nerves that go to the limbs.
TYPES OF MALIGNANT BRAIN TUMORS
The most common brain tumor in adults are gliomas. Gliomas make up 78% of malignant brain tumors. They come from glia which are the supporting cells of the brain. Gliomas can be divided into astrocytes, ependymal cells and oligodendroglial cells.
- Astrocytomas: These make up 50% of primary brain/ spinal cord tumors. They are also the most common type of glioma. Astrocytes are glial cells that are supportive tissue of the brain and this is where astrocytomas develop from. They mostly occur in the cerebellum. Astrocytomas mostly appear in adults but they can show up in all ages. Younger children usually get astrocytomas in the base of the brain and make up the majority of the brain tumors children get. These tumors are typically lower grade in children but higher grade in adults.
- Ependymomas: These are only 2-3% of brain tumors. They arise from a neoplastic change of the ependymal cells that line the ventricular system.
- Glioblastoma multiforme (GBM): This is an extremely invasive glial tumor. They will grow fast and spread to other tissues. The prognosis usually does not look good. These can be made up of multiple cells such as astrocytes and oligodendrocytes. GBM are mostly in men around the ages of 50 to 70 years old.
- Medulloblastomas: They usually show up in the cerebellum of children. While this is a high grade tumor, radiation and chemotherapy may help.
- Oligodendrogliomas: The cell that makes myelin make up these tumors. Myelin is the insulation for the structure of the brain.
OTHER TYPES OF BRAIN TUMORS
- Hemangioblastomas: These tumors grow slowly and are usually in the cerebellum. They come from blood vessels and are usually large. The tumor typically shows up with a cyst. These tumors are common in 40-60 years old men.
- Rhabdoid tumors: these tumors are extremely rare and also extremely aggressive. They can spread through the CNS. They sometimes appear in multiple areas such as the kidneys. They happen mostly in children but can also appear in adults.
PEDIATRIC BRAIN TUMORS
Brain tumors in children could appear from different tissues than adults. Younger children may have imparied development after treatments like radiation therapy.
Pediatric Brain Tumor Foundation says that nearly 4200 children are diagnosed with a brain tumor in the US. 72% of the diagnosed are 15 years old or younger. Most of the brain tumors are in the back of the brain. Children usually get hydrocephalus and their body is not functioning properly.
The brain tumors that appear most in children are medulloblastomas, low grade astrocytomas, ependymomas, craniopharyngiomas, and brainstem gliomas.
WORLD HEALTH ORGANIZATION
The WHO has created a scale system to indicate how benign or malignant a tumor is.
- Low grade
- Grade 1: most benign, likely curable, non infiltrative, grows slow, long term survival
Ex: Pilocytic astrocytoma, craniopharyngioma, gangliocytoma, ganglioglioma
- Grade 2: slow growing, a little infiltrative, can return as a higher grade
Ex: Diffuse astrocytoma, pineocytoma, pure oligodendroglioma
- High grade
- Grade 3: malignant, infiltrative, can come back as higher grade
Ex: anaplastic astrocytoma, anaplastic ependymoma, anaplastic oligodendroglioma
- Grade 4: Most malignant, grows fast, aggressive, infiltrative, often recurs, necrosis prone
Ex: Glioblastoma multiforme, pineoblastoma, medulloblastoma, ependymoblastoma
INCIDENCE IN ADULTS
The National Cancer Institute suggests nearly 22,910 adults will be diagnosed with a brain or nervous system tumor in 2012. In 2012, 13,700 of these tumors will cause death.
From 2005 to 2009, the median age for death from a brain tumor or nervous system tumors was 64 years old.
BRAIN TUMOR CAUSES
When particular genes on the chromosomes of a cell are not functioning properly, a brain tumor can arise. The cell may be dividing uncontrollably, have damaged genes, and apoptosis is not working correctly. Sometimes people can be born with partial defects to certain genes and environmental factors continue to do damage. Sometimes the only cause is environmental.
When a cell has uncontrolled division and unregulated growth, the cell can grow into a tumor. Tumors might make substances that inhibit the immune system from recognizing tumor cells and so the tumor cells will overpower anything inhibiting it’s growth.
Tumors that grow fast could need extra oxygen and nutrients than the blood supply for normal tissues. Angiogenesis factors can be made by tumors that make blood vessels grow. The tumor becomes reliant on these blood vessels for the extra nutrients and oxygen.
Symptoms will vary but can include:
- Trouble speaking and thinking
- Changes in personality
- Balance loss/ dizziness
- Vision changes
- Hearing changes
- Facial numbness
- Nausea, vomiting, swallowing issues
Imaging can show brain tumors. The imaging taken can include a CT scan and MRI. Intraoperative MRIs can be used to guide tissue biopsies and aid in removal of the tumor. MRS can be used to look at the chemical profile of the tumor. PET scans can be used to see if a brain tumor is recurring. A biopsy is sometimes the only way to make a sure diagnosis of a brain tumor. The surgeon and pathologist can see if the tumor is benign or malignant.
BRAIN TUMOR TREATMENT
Brain tumors are typically treated with surgery, radiation, or chemotherapy. This is determined case by case.
A surgeon will try to remove as much of the tumor as possible without damaging brain tissue. Neurosurgeons will usually enter the brain through a craniotomy to make sure they can access and remove as much tumor as possible. A drain can be put in the brain fluid cavities during surgery to drain brain fluid while the brain is in recovery.
A stereotactic biopsy can sometimes be performed before a craniotomy. This allows for the tissues to be examined for a complete diagnosis. A frame is attached to the head of the patient and a scan is obtained. The patient goes to the operating room to get a small hole drilled into the skull to get access to certain areas. A small sample will be taken and examined under a microscope.
Surgical navigation systems were introduced in the early 1990s. This helps guide the surgeon during the operation. This allows for tumors that have been deemed inoperable to be removed. A limitation to these systems is that they use a scan taken before surgery to guide the surgeon and cannot show movements in the brain during the operation.
Intraoperative language mapping is important for patients that have tumors that can affect language function like a dominant-hemisphere gliomas. The patient is awake during surgery to assess language function so the surgeon can decide where to resect.
Ventriculoperitoneal shunting can be needed. CSF in the brain and spine is always circulating. If the flow of CSF is inhibited, the sacs that contain CSF can grow in size and cause pressure on the brain. This leads to hydrocephalus. A shunt can divert the CSF away from the brain to decrease the pressure. The CSF usually is transferred to the peritoneal cavity. The shunt is often permanent. If the system does not work, the patient can get headaches, nausea, visual issues, confusion, lethargy. An endoscopic third ventriculostomy can divert fluid around the blockage without a shunt and may also be used.
Radiation therapy is using high energy X-rays to harm cancer cells and shrink tumors. If a tumor cannot be treated with surgery radiation could be used.
- Standard external beam radiotherapy uses multiple radiation beams to target the tumor and limit exposure to normal structures.
- Proton beam treatment uses a type of radiation where protons are directed to the tumor. Less tissue surrounding the tumor will be damaged
- Stereotactic Radiosurgery uses radiation to multiple beams on a target tissue. This damages less to tissues near the tumor.
For pediatric tumors, lymphomas, and some oligodendrogliomas, chemotherapy is helpful. Chemotherapy usually only improves about 20% of patients. Chemotherapy can cause lung scarring, suppression of the immune system, nausea, etc.
Chemotherapy causes cell damage that is repaired best by normal tissue rather than tumor tissue. Resistance to chemotherapy can cause survival of tumor tissues that cannot respond to the drug or the drug cannot pass into the brain from the bloodstream. The blood brain barrier is a barrier between the bloodstream and brain tissue. Sometimes chemotherapy disrupts the barrier or injects the drug into the tumor or the brain. The task is to block tumor growth.
In 1996, the US Food and Drug Administration approved chemotherapy-impregnated wafer which can be used by the neurosurgeon at surgery. The wafers slowly put the drug into the tumor and the patient can get chemotherapy without the side effects.
Laser thermal ablation is a new technique used on small tumors that may be difficult to reach. This places a small catheter within the area, completing a biopsy, then using a laser to remove the tumor.
Many new therapies are being researched. Right now being researched is immunotherapy, targeted toxins, anti-angiogenesis therapy, gene therapy, and differentiation therapy.