Overview of Brain Tumor Types
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A brain tumor is an abnormal growth of cells in or around the brain. Brain tumors can be benign (noncancerous) or malignant (cancerous) and can start in or on the brain itself (primary brain tumors) or spread to the brain from other parts of the body (secondary or metastatic brain tumors).
The effects of a brain tumor depend on its size, location, and type. Common symptoms include headache, nausea and vomiting, seizures, confusion, and vision or hearing problems. Brain tumors can be diagnosed using medical imaging techniques like magnetic resonance imaging (MRI) and computed tomography (CT) scans. Treatment options for brain tumors include surgery, radiation therapy, chemotherapy, and other medications, and depend on the type of tumor and its location.
Not every brain tumor causes the same symptoms or has the same long-term outlook, so a surgeon should identify the type of brain tumor you have to determine the best treatment. In this article, we’ll explain more about how brain tumors are categorized and give an overview of the different types of brain tumors.
How Are Tumors Categorized?
Brain tumors can be categorized in several different ways based on where the tumor originates, level of malignancy, original cell type, and location within the brain. It is helpful to become familiar with these terms because they are frequently used by medical and surgical professionals to describe your tumor and may be used when determining treatment.
- Primary vs. Secondary: Brain tumors that start in the brain are called primary brain tumors. Brain tumors that have spread from a tumor located somewhere else in the body, such as tumors in the lungs or breasts, are called secondary or metastatic tumors.
- Benign vs. Malignant: Brain tumors can also be categorized based on how aggressive they are. Slow-growing and less invasive tumors are considered benign (noncancerous). Aggressive fast-growing brain tumors that invade healthy brain tissue or spread to surrounding tissues are considered malignant (cancerous).
- Original Cell Type: Another way brain tumors are categorized is by the type of cell they are made of. Glial cells are the support cells of the brain. Brain tumors can be categorized as glial (composed of glial cells such as astrocytes, ependymal cells, and oligodendroglia) or non-glial (developed on or in other structures of the brain).
- Location: Brain tumors in adults are likely to be found above the tentorium, which is a membrane that separates the cerebellum from the lobes of the brain; these tumors are referred to as supratentorial. In contrast, brain tumors in children often form below the tentorium and are described as infratentorial.
What Are the Different Types of Brain Tumors?
There are many different types of brain tumors, but the ones described below are the 3 most common types:
- Meningioma: This type of tumor starts in the meninges, which are the protective layers surrounding the brain and spinal cord. Meningiomas are usually slow-growing benign tumors, but they can still cause symptoms by putting pressure on nearby structures like brain, nerves, and blood vessels. Meningiomas are often found during an exam or scan for a different medical reason. They occur more often in women, possibly because these tumors carry estrogen receptors. Meningiomas are also more common in older persons, but they can occur in younger patients who previously received brain radiation therapy.
- Glioma: This type of tumor starts growing from the supportive tissue of the brain, called glial cells. Glial cells provide support and protection for the neurons (nerve cells) in the brain. Gliomas can be somewhat benign or malignant, and include subtypes such as astrocytomas, oligodendrogliomas, and ependymomas.
- Pituitary tumor: These tumors develop in the pituitary gland, which is located at the base of the brain and controls the production of hormones responsible for growth, metabolic, reproductive, and other body functions. Pituitary tumors can be mostly benign or rarely malignant and may lead to hormonal imbalances.
These 3 types of tumors make up 80% of all brain tumors. Within these, there are several related subtypes:
- Astrocytoma: Originate from astrocytes (cells that support nerve cells). Astrocytomas can grow slowly (low grade) or fast (high grade) are found in the brain or spinal cord.
- Oligodendroglioma: Rare, slow-growing tumors that develop from oligodendrocytes (glial cells that support and myelinate (insulate) nerve cells in the central nervous system). They are primarily located in the frontal lobes of the brain.
- Ependymoma: Originate from the epithelial lining of the ventricles (4 cavities in the brain that cerebrospinal fluid passes through). When found in the fourth (lowest) ventricle, they cause obstructive hydrocephalus — an accumulation of cerebrospinal fluid within the brain that is associated with a less favorable outlook.
- Glioblastoma (GBM): Aggressive, high-grade, malignant astrocytomas. These tumors are also referred to as brain cancer.
- Pilocytic astrocytoma: Benign, low-grade, well-defined astrocytomas. They often appear in the cerebellar region and usually have a good prognosis.
- Pituitary adenoma: Benign tumors that develop in the pituitary gland. Some are “functional,” meaning they overproduce various key hormones that are then released into the bloodstream, whereas others can result in the underproduction of hormones.
Important note: Brain metastases account for approximately 50% of all brain tumors. Metastatic brain tumors originate elsewhere in the body and metastasize (spread) to the brain. Common primary tumors that metastasize to the brain include melanoma, lung, breast, colon, and kidney tumors.
Less Common Brain Tumor Types
Rare brain tumors are those that are less commonly seen and can be more challenging to diagnose and treat. Some of the rarer brain tumor types include the following:
- Chordoma: Benign, slow-growing tumors commonly located at the skull base or the lower spine. They can apply pressure on nearby neural tissue (responsible for transmitting and processing sensory information and coordinating movement and other bodily functions).
- Craniopharyngioma: Relatively benign but often recur, supratentorial tumors. These tumors can cause compression of the optic chiasm (where visual information is transmitted from the eyes to the brain), leading to defects in vision, or of the nearby pituitary gland, resulting in problems with growth, metabolism, and reproductive function.
- Acoustic neuroma: Also known as vestibular schwannomas, are derived from Schwann cells, which are responsible for insulating peripheral nerves. These tumors can cause hearing loss, ringing in the ear, and balance problems.
- Hemangioblastoma: Tumors originating from blood vessels. They are commonly found in the cerebellar region at the base of the brain and can be associated with inherited conditions, such as von Hippel-Lindau syndrome, which can cause tumors in various parts of the body.
- Gangliocytoma: Tumors composed of gangliocytes (neuron cells in the central nervous system). They may be classified as well-differentiated gangliocytomas (composed of cells that grow slowly and look like normal cells) or anaplastic gangliocytomas (composed of cells that divide rapidly and look little or nothing like normal cells).
- Pinealoma: Rare tumors of the pineal gland that most commonly occur in children younger than 12 years of age. They may cause obstructive hydrocephalus, a disruption of cerebrospinal fluid flow that results in increased pressure within the skull. Pinealomas may produce b-HCG, a hormone that leads to early puberty.
- Medulloblastoma: Highly malignant cancer that most commonly occurs in children. They are often found in the cerebellum, where they produce symptoms such as a wide-based, uncoordinated manner of walking.
Differences Between Brain Tumors in Adults and Children
Brain tumors can occur in people of all ages, but the symptoms and treatment options can be different between children and adults, and diagnosis may be more difficult in children because they cannot always clearly describe their symptoms. Certain types of tumors also are more common in certain age-groups, which we have outlined below.
Metastatic brain tumors that have spread from other tumor sources are the most common type in adults. Of primary brain tumors, meningioma is most common in adults, accounting for 30% of cases. Because meningiomas are most often located near the surface of the brain, they are easier to remove with surgery and have an excellent prognosis.
Glioblastoma is the most common primary malignant brain cancer in adults and is associated with a less favorable outlook. Other common brain tumors in adults include pituitary adenomas, acoustic neuromas, oligodendrogliomas, and hemangioblastomas.
The most common brain tumors in young adults are pituitary adenomas. This benign tumor affects the pituitary gland, which is a small gland located at the base of the brain that regulates hormones.
Craniopharyngiomas are more common in children, but they can also occur in young adults. A relatively benign tumor that unfortunately often recurs, craniopharyngioma affects the pituitary gland and the hypothalamus, which regulate important functions like growth and hormone regulation. Meningiomas and gliomas can also affect young adults, although gliomas are more common in older adults.
Brain tumors in children are rare, but they can have a significant impact on a child's health and development. The types of brain tumor most likely to be found in children include:
- Pilocytic astrocytoma: A slow-growing, benign tumor that is the most common primary brain tumor found in children.
- Medulloblastoma: A malignant tumor that originates in the brain's cerebellum and is the most common malignant brain tumor to occur in children.
- Craniopharyngioma: A benign tumor affecting the pituitary gland and the hypothalamus, which regulate important functions like growth and hormone regulation.
- Ependymoma: A type of tumor found in children that starts in the cells that line the ventricles of the brain and spinal cord.
- Diffuse intrinsic pontine glioma (DIPG): An aggressive tumor that grows in the brainstem and is usually diagnosed when children are 5 to 7 years of age; sometimes called a brainstem glioma.
- Pinealoma: A tumor that may be benign or malignant and occurs in or around the pineal gland, which produces melatonin and regulates the body’s sleep-wake cycle
Benign and Malignant Brain Tumor Types
Benign, or noncancerous, brain tumors are usually slow growing and have little potential to spread. Common benign primary brain tumors include:
- Craniopharyngioma (although this tumor often recurs)
- Well-differentiated gangliocytoma
- Some pinealomas
- Most pituitary adenomas
- Acoustic neuroma
Malignant brain tumors are more aggressive and carry a high risk of spreading to surrounding tissues. Glial tumors comprise approximately 78% of malignant brain tumors. These brain tumors are often described using a grading system. The grade of the tumor (roman numerals I-IV) is determined by specific microscopic features that indicate aggressive behavior.
- Grade I tumors are slow growing, unlikely to spread, and often treated with surgery alone.
- Grade II tumors are less likely to grow and spread, but they may come back after surgery.
- Grade III tumors have cells that are more abnormal than those of a grade I or II tumor. These cells tend to grow and divide more quickly, and are more likely to spread to other parts of the body.
- Grade IV tumors are the highest grade of tumors (are considered cancerous) and are characterized by rapidly dividing cancer cells surrounding an area of dead cells (necrosis). These tumors are often surrounded by new blood vessels, which help maintain a tumor’s rapid growth.
Glioblastoma is the most common malignant primary brain tumor in adults. It is a grade IV glial tumor — the highest, most aggressive grade — and is known as the deadliest brain tumor. Astrocytoma is the most common type of glioma; they are commonly low grade in children but high grade in adults. Other tumors that carry a high risk of malignancy include ependymomas, oligodendrogliomas, anaplastic gangliocytomas, and medulloblastomas. Metastatic (secondary) brain tumors can also behave aggressively in the brain.
- A brain tumor is an abnormal growth of cells in the brain, and the effects you experience depend on its size, location, and type.
- Brain tumors are categorized based on tumor origin (primary vs. secondary), level of malignancy, original cell type, and location within the brain.
- Brain tumors can occur in people of all ages, but certain types of tumors are more common in certain age-groups.
- Not every brain tumor causes the same symptoms or has the same long-term outlook, so it’s important for a doctor to identify the type of brain tumor you have to determine the best treatment.