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Frequently Asked Questions
What are the different types of brain tumors?
There are many different kinds of brain tumors.
The first way to divide brain tumors is based on whether they are primary
or secondary. Primary tumors are tumors that begin in the brain.
Secondary tumors are tumors that started our elsewhere in the body and
spread, or metastasized, to the brain. For example, secondary brain
tumors could have begun as breast cancer or lung cancer.
Primary brain tumors can be further divided based on what type of cell the tumor
began as. Some types of primary brain tumors are astrocytomas, oligodendrogliomas, meningiomas,
medulloblastomas, neuronomas, ependymomas, craniopharingiomas, pineal tumors,
germ cell tumors, and schwannomas. The name of a tumor depends on
what kind of cell it comes from. Astrocytomas come from astrocytes,
oligodendrogliomas from oligodendrocytes, meningiomas from meningeal cells,
medulloblastomas from medulloblasts, etc. For more information on
specific tumor types (and treatments) go to National Cancer Institute's Brain Tumor Information Page.
What is a glioma?
A glioma is a tumor of the glial cells. Glial
cells are the supportive cells of the central nervous system; they help
neurons, nerve cells, do their jobs. Glial cells include astrocytes,
oligodendrocyts, and ependymal cells, so gliomas can be astrocytomas, oligodendrogliomas,
or ependymomas. Gliomas are the
most common type of primary brain tumor, but not every brain tumor is a
glioma. Because there are different types of gloimas and because factors
such as patient age or tumor location can affect tumor behavior, two people with
gliomas may have very different experiences.
What are the parts of the brain?
The brain is complicated organ that is only partially
understood. There are several references on the web that explain
what the parts of the brain are, where they are, what they do, and what
might happen if they are damaged, including
http://www.waiting.com/brainanatomy.html.
What does grade mean?
Grading is a way of telling how bad a tumor is.
The grade of a tumor depends on how the cells look to a pathologist using
a microscope. Generally, higher grade tumors look less like the specialized
cells they came from and more like unspecialized cells that can divide indefinitely.
Such cells are described as anaplastic, so tumors that are described as anaplastic
are often higher grade than those that are not.
Many patients have the grade of their tumor change
during the course of the disease. This change can happen for two
reasons. First, tumors can become more aggressive, making them a higher
grade than they were initially. Second, the grade is based entirely on the piece
of a tumor removed for a biopsy. Tumors are often heterogeneous,
so one part of a tumor may be one grade and another part of a tumor another
grade. The pathologist will usually assign to a tumor the highest
grade he or she sees, but there may be higher grade cells lurking elsewhere,
especially if the biopsy sample is small. Although there are rules for determining tumor type
and grade, it is as much an art as a science. Therefore, it is important
to have your biopsy samples looked at by a neuropathologist who sees a
large number of brain tumors.
The most common system for grading gliomas is called
the WHO system because it is approved by the World Health Organization.
In the WHO system, there are four grades of astrocytomas. Grade I
are the slowest growing, least aggressive tumors and grade IV are the fastest
growing, most aggressive tumors. In the WHO system, grade III is
synonymous with anaplastic astrocytomas and grade IV is synonymous with
glioblastoma multiforme. For a detailed description of this system for all types
of gliomas and a chart showing how it compares
to a couple of other systems for grading astrocytomas, go to http://neurosurgery.mgh.harvard.edu/newwhobt.htm
. One system not included in that link ranks tumors from 1 to 3, with 1 combining
WHO grades I and II, 2 being equivalent to WHO grade III, and 3
being glioblastomas. There are also other systems used at individual
institutions, so it is worth asking a doctor to explain what system he or she
is using.
My doctor says a brain tumor is not cancer. Is that true?
Technically, yes. A tumor is cancerous
if it will spread, or metastasize, beyond it's original site to other parts
of the body. Primary brain tumors rarely, if ever, spread outside
the brain, so they are not technically cancer. However, psychologically
and practically, brain tumors are a lot like cancerous tumors. The
treatments are often the same, and resources that are helpful to cancer
patients, such as cancer support groups, the American Cancer Society, and
the National Cancer Institute, are helpful to patients with brain tumors.
Is a benign brain tumor safe?
There are two meanings of the word benign
in reference to brain tumors. Just as brain tumors are not cancerous,
brain tumors are benign because they do not spread outside the brain.
However, growths in the brain are dangerous because of the importance of
the brain and the limited amount of space inside the skull. Therefore,
this meaning of the word benign is meaningless and misleading when applied
to brain tumors.
Brain tumors are often divided between benign and
malignant tumors based on grade. Low grade tumors are considered
benign, while high grade tumors are considered malignant. Generally,
the term malignant includes grade III and IV astrocytomas, including glioblastoma
multiforme, and grade III oligodendroglioma. In this division, benign
tumors are slower growing and less intertwined with normal brain tissue
than malignant tumors. Benign tumors often can be removed more completely
and respond better to treatment than malignant tumors.
If you have a question not answered here or a suggestion about questions
or answer, let us know.
Last Updated: 7/10/2003
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