Brain tumors: an introduction
A tumor (also called a neoplasm
or lesion) is abnormal tissue that grows by
uncontrolled cell division. Normal cells grow
in a controlled manner as new cells replace
old or damaged ones. For reasons not fully understood,
tumor cells reproduce uncontrollably.
Brain tumors are named after the cell type from
which they grow. They may be primary (starting
in the brain) or secondary (spreading to the
brain from another area). Treatment options
vary depending on the tumor type, size and location;
whether the tumor has spread; and the age and
medical health of the person. Treatment options
may be curative or focus on relieving symptoms.
Of the more than 120 types of brain tumors,
many can be successfully treated. New therapies
are improving the life span and quality of life
for many people.
What is a brain tumor?
A primary brain tumor is an abnormal growth that starts in the brain
and usually does not spread to other parts of
the body. Primary brain tumors may be benign
A benign brain
tumor grows slowly, has distinct boundaries,
and rarely spreads. Although its cells are
not malignant, this tumor composed of benign
cells and located in vital areas can be considered
A malignant brain tumor grows
quickly, has irregular boundaries, and spreads
to nearby brain areas. Although they are sometimes
called brain cancer, malignant brain tumors
do not fit the definition of cancer because
they do not spread to organs outside the brain
and spinal cord.
brain tumors begin as cancer elsewhere
in the body and spread to the brain. They form
when cancer cells are carried in the blood stream
to the brain. The most common cancers that spread
to the brain are lung and breast.
Whether a brain tumor is benign,
malignant, or metastatic, all are potentially
life-threatening. Enclosed within the bony skull,
the brain cannot expand to make room for a growing
mass. As a result, the tumor compresses and
displaces normal brain tissue (Fig. 1). Some brain tumors
cause a blockage of cerebrospinal fluid (CSF)
that flows around and through the brain. This
blockage increases intracranial pressure and
can enlarge the ventricles (hydrocephalus).
Some brain tumors cause swelling (edema). Size,
pressure, and swelling all create "mass
effect," which cause many of the symptoms.
Figure 1. Brain tumors may grow from nerves (neuroma), dura (meningioma), pituitary gland (craniopharyngioma or pituitary adenoma). They may also grow from the brain tissue itself (glioma). As they grow they may compress normal tissue and cause symptoms.
Types of brain tumors
There are over 120 different types
of brain tumors. Common brain tumors include:
- Pilocytic Astrocytoma (grade I)
- Diffuse Astrocytoma (grade II)
- Anaplastic Astrocytoma (grade III)
- Glioblastoma Multiforme (grade IV)
- Oligodendroglioma (grade II)
- Anaplastic Oligodendroglioma (grade
- Ependymoma (grade II)
- Anaplastic Ependymoma (grade III)
Pinealoma (pineocytoma, pineoblastoma)
The World Health Organization (WHO) developed
a classification and grading system to standardize
communication, treatment planning, and predict
outcomes for brain tumors. Tumors are classified
by their cell type and grade by viewing the
cells, usually taken during a biopsy, under
Cell type. Refers to the
cell of origin of the tumor. For example,
nerve cells (neurons) and support cells (glial
and schwann cells) give rise to tumors. About
half of all primary brain tumors grow from
glial cells (gliomas). There are many types
of gliomas because there are different kinds
of glial cells.
Grade. Refers to the way
tumor cells look under the microscope and
is an indication of aggressiveness (e.g.,
low grade means least aggressive and high
grade means most aggressive) (Table 1). Tumors
often have a mix of cell grades and can change
as they grow. Differentiated and anaplastic
are terms used to describe how similar or
abnormal the tumor cells appear compared to
Table 1. Glioma Grading Scale
Slow growing cells
Almost normal appearance
Usually associated with long-term
Relatively slow growing cells
Slightly abnormal appearance
Can invade nearby tissue
Sometimes recur as a higher grade
Actively reproducing abnormal cells
Infiltrate normal tissue
Tend to recur, often as a higher grade
Rapidly reproducing abnormal cells
Very abnormal appearance
Area of dead cells (necrosis) in center
Form new blood vessels to maintain
What causes brain tumors?
Medical science neither knows what causes
brain tumors nor how to prevent primary tumors
that start in the brain. People most at risk
for brain tumors include those who have:
- cancer elsewhere in the body
- prolonged exposure to pesticides, industrial
solvents, and other chemicals
- inherited diseases, such as neurofibromatosis
What are the symptoms?
Tumors can affect the brain by
destroying normal tissue, compressing normal
tissue, or increasing intracranial pressure.
Symptoms vary depending on the tumor’s
type, size, and location in the brain (Fig.
2). General symptoms include:
- headaches that tend to worsen in the morning
- stumbling, dizziness, difficulty walking
- speech problems (e.g., difficulty finding
the right word)
- vision problems, abnormal eye movements
- weakness on one side of the body
- increased intracranial pressure, which
causes drowsiness, headaches, nausea and vomiting,
Figure 2. Brain tumor symptoms are related to the functional
areas of the brain, giving doctors clues as
to the tumor location.
Specific symptoms include:
lobe tumors may cause behavioral and emotional
changes, impaired judgment, impaired sense of smell, memory loss,
paralysis on one side of the body,
reduced mental abilities, and vision loss.
- Parietal lobe tumors
may cause impaired speech,
inability to write,
lack of recognition, and spatial disorders.
- Occipital lobe tumors
may cause vision loss in one
or both eyes.
- Temporal lobe tumors
may cause impaired speech and memory difficulty.
- Brainstem tumors may
cause behavioral and emotional
changes, difficulty speaking and swallowing,
drowsiness, hearing loss, muscle weakness on one side of the face
(e.g., head tilt, crooked smile), muscle weakness on one side of the body, uncoordinated gait,
drooping eyelid or double vision, and vomiting.
- Pituitary gland tumors
may cause increased secretion
of hormones (Cushing’s Disease,
acromegaly), a stop in menstruation, abnormal secretion of milk, and decreased libido.
Who is affected?
The American Brain Tumor Association estimates
that about 78,000 people will be diagnosed with
a primary brain tumor in the US this year. Metastatic (secondary)
brain tumors are more common than primary brain
tumors by at least 10 to 1, and they occur in
20% to 40% of cancer patients. The exact number
of brain metastases is unknown, but it has been
estimated that 200,000 to 300,000 people are
diagnosed in the US each year. Unfortunately,
each year about 17,000 people die of brain tumors
in the US. Although brain tumors can occur at
any age, they are most common in children 3
to 12 years old and in adults 40 to 70 years
How is a diagnosis made?
First, the doctor will obtain your personal
and family medical history and perform a complete
physical examination. In addition to checking
your general health, the doctor performs a neurological
exam to check mental status and memory, cranial
nerve function (sight, hearing, smell, tongue
and facial movement), muscle strength, coordination,
reflexes, and response to pain. Additional tests
- Audiometry, a hearing test performed by
an audiologist, detects hearing loss due to
tumors near the cochlear nerve (e.g., acoustic
- An endocrine evaluation measures hormone
levels in your blood or urine to detect abnormal
levels caused by pituitary tumors (e.g., Cushing’s
- A visual field acuity test is performed
by a neuro-ophthalmologist to detect vision
loss and missing areas in your field of view.
- A lumbar puncture (spinal tap) may be performed to examine cerebrospinal fluid for tumor cells, proteins, infection, and blood.
Tomography (CT) scan is a safe, noninvasive
test that uses an X-ray beam and a computer
to make 2-dimensional images of the brain.
Similar to an MRI, it views the brain in slices,
layer-by-layer, taking a picture of each slice.
A dye (contrast agent) may be injected into
your bloodstream. CT is especially useful
for viewing changes in bony structures.
Resonance Imaging (MRI) scan is a noninvasive
test that uses a magnetic field and radiofrequency
waves to give a detailed view of the soft
tissues of the brain. It views the brain 3-dimensionally
in slices that can be taken from the side
or from the top as a cross-section. A dye
(contrast agent) may be injected into your
bloodstream. MRI is very useful to evaluate
brain lesions and their effects on surrounding
brain (Fig. 3).
Figure 3. MRI scans of a benign and malignant brain tumor. Benign tumors have well defined edges and are more easily removed surgically. Malignant tumors have an irregular border that invades normal tissue with finger-like projections making surgical removal more difficult.
If a diagnosis
cannot be made clearly from the scans, a biopsy
may be performed to determine what type of tumor
is present. Biopsy is a procedure to remove
a small amount of tumor cells to be examined by a
pathologist under a microscope. A biopsy can
be taken as part of an open surgical procedure
to remove the tumor or as a separate diagnostic
procedure, known as a needle biopsy via a small
hole drilled in the skull . A hollow needle is
guided into the tumor and a tissue sample is
removed (Fig. 4). A stereotactic biopsy is like a needle
biopsy but is performed with the use of a stereotactic
frame and a computer to precisely locate
the tumor and direct the needle. This more complex
procedure is used for deep tumors in critical
Figure 4. During a needle biopsy, a hollow cannula is inserted into the tumor. Small biting instruments remove bits of tumor for the pathologist to examine and determine the exact tumor cell type.
Who treats brain tumors?
Because there are so many kinds of brain tumors
and some are complex to treat, many doctors
may be involved in your care. Your team may
include a neurosurgeon, oncologist, radiation
oncologist, radiologist, neurologist, and neuro-ophthalmologist.
What treatments are available?
Treatment options vary depending on the type,
grade, size and location of the tumor; whether
it has spread; and your age and general health.
The goal of treatment may be curative or focus
on relieving symptoms (palliative care). Treatments
are often used in combination with one another.
The goal is to remove all or as much of the
tumor as possible through surgery to minimize
the chance of recurrence. Radiation therapy
and chemotherapy are used to treat tumors that
cannot be removed by surgery alone. For example,
surgery may remove the bulk of the tumor and
a small amount of residual tumor near a critical
structure can later be treated with radiation.
Sometimes the best treatment is observation.
For example, benign, slow growing tumors that
are small and have few symptoms may be observed
with routine MRI scans every year until their
growth or symptoms necessitate surgery. Observation
may be the best option for older patients with
other health conditions.
Medications are used to control
some of the common side effects of brain tumors.
- Corticosteroid medications, such as dexamethasone
(Decadron), are prescribed to reduce swelling
and inflammation around the tumor. Because
steroid medications can cause stomach ulcers
and gastric reflux, famotidine (Pepcid) or
pantoprazole (Protonix) are prescribed to
reduce the amount of acid produced in the
- Furosemide (Lasix) or mannitol (Osmitrol)
may be used to control edema and intracranial
- Anticonvulsant medications are used to prevent
or control seizures. The most common ones
include phenytoin (Dilantin), valproic acid
(Depakote), carbamazepine (Tegretol), and
Surgery is the treatment of choice for brain tumors that can be reached without causing major injury to vital parts of the brain. Surgery can help to refine the diagnosis, remove as much of the tumor as possible, and release pressure within the skull. A neurosurgeon performs a craniotomy to open the skull and remove the tumor (Fig 5). Sometimes
only part of the tumor is removed if it is near critical areas of the brain. A partial removal can still relieve symptoms. Radiation or chemotherapy may be used on the remaining tumor cells.
Improvements in techniques, particularly image-guided surgery, intraoperative MRI/CT, and functional brain mapping have improved the surgeon’s ability to precisely locate the tumor, define the tumor’s borders, avoid injury to vital brain areas, and confirm the amount of tumor removal while in the operating room.
Figure 5. Surgery involves cutting a window in the skull (craniotomy) to remove the tumor.
therapy uses controlled high-energy rays
to treat brain tumors. Radiation works by damaging
the DNA inside cells making them unable to divide
and reproduce. The goal of radiation therapy
is to maximize the dose to abnormal cells and
minimize exposure to normal cells. The benefits
of radiation are not immediate but occur over
time. Aggressive tumors, whose cells divide
rapidly, typically respond more quickly to radiation.
There are two ways to deliver radiation, external
and internal beams.
External beam radiation is delivered from outside
the body by a machine that aims high-energy
rays (x-rays, gamma rays) at the tumor (Fig. 6).
Figure 6. A machine rotates around the patient, aiming radiation beams at the tumor. The radiation beams are shaped to match the tumor and minimize exposure to normal brain tissue.
- Stereotactic radiosurgery (SRS) delivers a high dose of radiation during a single session. Although it is called surgery, no incision is made.
- Fractionated stereotactic radiotherapy
(FSR) delivers lower doses of radiation
over many visits. Patients return daily over
several weeks to receive the complete radiation
- Whole brain radiotherapy (WBRT) delivers the radiation dose to the entire brain. It is often used to treat multiple brain tumors and metastases.
Internal radiation (brachytherapy)
is delivered from inside the body by surgically
placing radioactive material (sealed in catheters,
seeds, or balloons) directly into the
tumor. After the patient undergoes a craniotomy
to remove the tumor, the radioactive material
is placed inside the tumor cavity. The radiation
dose is delivered to the first few millimeters
of tissue that surrounded the tumor cavity where
malignant cells may still remain. Patients have
no risk of radiation injury to other parts of
their own body or to others around them because
the radiation dose is precisely delivered and
Chemotherapy drugs work by interrupting cell
division. However, it affects not only tumor
cells but normal cells, thus causing side effects,
especially in fast growing cells (e.g., hair,
digestive, blood). Treatment is delivered in
cycles with rest periods in between to allow
the body to rebuild healthy cells.
Chemotherapy drugs can be administered orally
as a pill, intravenously (IV), or as a wafer
placed surgically into the tumor. The drugs
most commonly used to treat brain tumors are
carmustine (BCNU), lomustine (CCNU), and temozolomide
(Temodar). Chemotherapy is also used as a radio-sensitizing
agent that increases tumor cell death during
radiation therapy. Agents that often work in
high-grade gliomas include procarbazine, platinum
analogs (cisplatin, carboplatin), the nitrosureas
(BCNU, CCNU), and alkylating agents (temozolomide,
vincristine). BCNU has been proven effective
when applied locally to the tumor bed after
the tumor has been removed. By applying it directly
to the diseased area of the brain, side effects
are limited and the drug has a more beneficial
effect. Chemotherapy is not routinely used for
Figure 7. Chemotherapy for high-grade gliomas is usually taken as a pill daily for a set period of time called a cycle. The drug circulates through the bloodstream to the brain where it crosses the blood-brain-barrier to the tumor.
- Immunotherapy or biotherapy activates the
immune system (T-cells and antibodies) to
destroy cancer cells. Experimental research
is exploring ways to prevent or treat cancer
- Gene therapy uses viruses or other vectors
to introduce new genetic material into tumor
cells. This experimental therapy can cause
tumor cells to die or increase their susceptibility
to other cancer therapies.
- Hyperbaric oxygen uses oxygen at higher
than normal levels to promote wound healing
and help fight infection. It may also improve
the tumor’s responsiveness to radiation
and is being studied experimentally. Currently
it is being used to help the body naturally
remove dead tumor cells and treat radiation
Clinical trials are research studies in which new treatments—drugs, diagnostics, procedures, and other therapies—are tested in people to see if they are safe and effective. Research is always being conducted to improve the standard of medical care. Information about current clinical trials, including eligibility, protocol, and locations, are found on the Web. Studies can be sponsored by the National Institutes of Health (see clinicaltrials.gov) as well as private industry and pharmaceutical companies (see www.centerwatch.com).
Recovery & prevention
Your primary care doctor and oncologist should
discuss any home care needs with you and your
family. Supportive measures vary according to
your symptoms. For example, canes or walkers
can help those having trouble walking. A plan
of care to address changes in mental status
should be adapted to each patient’s needs.
Driving privileges may be suspended while taking
anticonvulsant medication. As each state has
different rules about driving and seizures,
discuss this issue with your doctor.
It may also be appropriate to discuss advance
medical directives (e.g., living will, health
care proxy, durable power of attorney) with
your family to ensure your medical care and
wishes are followed.
Because brain tumors develop in parts of the
brain that control movement, speech, vision
and thinking, rehabilitation may be a necessary
part of recovery. Although the brain can sometimes
heal itself after the trauma of treatment, it
will take time and patience. A neuropsychologist
can help patients evaluate changes caused by
their brain tumor and develop a plan for rehabilitation.
A neuropsychological evaluation assesses the
patient's emotional state, daily behavior, cognitive
(mental) abilities, and personality.
Physical therapy, occupational therapy, and
speech therapy may be helpful to improve or
correct lost functions.
How well a tumor will respond to treatment,
remain in remission, or recur after treatment
depends on the specific tumor type and location.
A recurrent tumor may be a tumor that still
persists after treatment, one that grows back
some time after treatment destroyed it, or a
new tumor that grows in the same place as the
When a brain tumor is in remission, the tumor
cells have stopped growing or multiplying. Periods
of remission vary. In general, benign tumors
recur less often than malignant ones.
Since it is impossible to predict whether or
when a particular tumor may recur, lifelong
monitoring with MRI or CT scans is essential
for people treated for a brain tumor, even a
benign lesion. Follow-up scans may be performed
every 3 to 6 months or annually, depending on
the type of tumor you had.
Sources & links
If you have more questions, please contact
Mayfield Brain & Spine at 800-325-7787 or 513-221-1100.
Support groups provide an opportunity for patients
and their families to share experiences, receive
support, and learn about advances in treatments
anaplastic: when cells divide
rapidly and bear little or no resemblance to
normal cells in appearance or function.
astrocytoma: a tumor arising
in the supportive cells (astrocytes) of the
brain or spinal cord; most often in the cerebrum.
benign: does not invade nearby
tissues or spread; noncancerous.
biopsy: a sample of tissue
cells for examination under a microscope to
determine the existence or cause of a disease.
brachytherapy: a type of radiation
therapy where capsules containing radioactive
substances are surgically implanted into the
tumor to deliver radiation; also called internal
cancer: generic term for more than
100 different diseases caused by uncontrolled,
abnormal growth of cells. Cancer cells can invade
and destroy normal tissue, and can travel through
the bloodstream and lymphatic system to reach
other parts of the body.
chemotherapy: treatment with
toxic chemicals (e.g., anticancer drugs).
chondrosarcoma: a rare, malignant bone tumor
arising from primitive notochord cells and composed
chordoma: a rare, bone tumor
arising from primitive notochord cells; usually
occurs at the base of the spine (sacrum) or
at the skull base (clivus).
craniopharyngioma: a benign tumor arising from
cells located near the pituitary stalk.
differentiation: refers to how developed
cancer cells are in a tumor. Well-differentiated
tumor cells resemble normal cells and tend to
grow and spread at a slower rate than undifferentiated,
which lack the structure and function of normal
cells and grow uncontrollably.
edema: tissue swelling caused
by the accumulation of fluid.
ependymoma: a tumor arising
from the ependyma cells lining the ventricles
of the brain and central canal of the spinal
epidermoid: a benign, congenital tumor
arising from ectodermal cells; also called pearly
glioma: any tumor arising
from glial tissue of the brain, which provides
energy, nutrients, and other support for nerve
cells in the brain.
hydrocephalus: an abnormal
build-up of cerebrospinal fluid usually caused
by a blockage of the ventricular system of the
brain; also called “water on the brain.”
immunotherapy: treatment designed
to improve or restore the immune system’s
ability to fight infection and disease.
intracranial pressure (ICP): pressure within the skull. Normal ICP is 20
lesion: a general term that
refers to any change in tissue, such as tumor,
blood, malformation, infection, or scar tissue.
lymphoma: a rare tumor arising
from lymph cells; may metastasize to the brain
from lymphoma tumor elsewhere in the body.
malignant: having the properties
of invasive growth and ability to spread to
mass effect: damage to the brain due
to the bulk of a tumor, the blockage of fluid,
and/or excess accumulation of fluid within the
medulloblastoma: a tumor arising
from primitive nerve cells; most often in the
meningioma: a tumor arising
from the meninges, the membrane that surrounds
the brain and spinal cord.
metastasis: the spreading of
metastatic: cancerous tumor
that has spread from its original source through
the blood or lymph systems.
oligodendroglioma: a tumor
arising from the support cells (oligodendroglia)
that produce myelin, the fatty covering around
pituitary adenoma: a tumor
arising from cells in the pituitary gland; tumor
may be hormone-secreting (prolactin, adrenocorticotropic,
growth hormone) or not.
radiation: high-energy rays
or particle streams used to treat disease.
schwannoma (also called neuroma): a tumor arising from Schwann cells that produce
stereotactic: a precise method
for locating deep brain structures by the use
of 3-dimensional coordinates.
tumor: an abnormal growth of
tissue resulting from uncontrolled multiplication
of cells and serving no physiological function;
can be benign or malignant.
updated > 3.2018
reviewed by > Ronald Warnick, MD, Christopher McPherson, MD, Mayfield Clinic
Mayfield Certified Health Info materials are written and developed by the Mayfield Clinic. We comply with the HONcode standard for trustworthy health information. This information is not intended to replace the medical advice of your health care provider.