Pathologist Peter Pytel, MD
Neuropathologist Peter Pytel, MD, left, is an expert in the examination of nervous system tissues, a role that plays a critical step in the diagnosis and identification of specific types of brain tumors.

Primary Brain Tumors

A brain tumor is a mass formed by abnormal cells growing in the brain. Most are thought to be caused by random cell mutations that take place as we age. Some tumors are caused by inherited genetic conditions like neurofibromatosis, von Hippel-Lindau disease and tuberous sclerosis. In rare instances, they may also be caused by treatments for another cancer.

Primary tumors are growths that start in the brain. These tumors grow and behave differently from other cancers; they usually do not spread to other parts of the body. Most of these tumors do not spread outside of the brain or spinal cord. They cause problems by pushing on the brain or growing into it. Symptoms can include headaches, seizures, weakness or difficulty speaking – the type of symptom is related to the location of the tumor in the brain. 

Physicians use the World Health Organization (WHO) grading system to describe how aggressive a tumor is. These grades range from I to IV. Grade I tumors grow very slowly, while grade IV tumors grow very quickly and are considered aggressive. Sometimes slower-growing tumors are classified as “low-grade” to set them apart from fast-growing “high-grade” tumors.


Gliomas are created by glial cells, which help make up the connective tissue of the brain. Gliomas can grow anywhere in the central nervous system and can affect your movements, speech, thought, emotion, balance or vision. Some gliomas are caused by genetic disorders. Exposure to radiation may also play a role in rare cases. Types of gliomas include:

  • Glioblastomas are the most common aggressive, high-grade brain tumor in adults. They are one of the fastest-growing types of brain tumors. Different types of glioblastomas can now be identified.
  • Astrocytomas are a group of tumors that include slow growing, low-grade tumors as well as high-grade tumors. High-grade astrocytomas can be as aggressive as glioblastomas. The type of astrocytoma determines how it behaves and should be treated. 
  • Oligodendrogliomas start from oligodendrocytes, the cells responsible for making the insulating fatty foam around nerve cells in brain tissue. Oligodendrogliomas are almost exclusively found in adults. 
  • Ependymomas grow from cells that line the fluid-filled spaces (ventricles) in the brain and related cells in the spinal cord. Where these tumors grow depends on the age of the patient. Most are low-grade. 


Meningiomas are one of the most common tumors in the brain. They grow from the surface coverings of the brain called the meninges. They typically grow on the brain rather than in it. They can compress brain or spinal cord tissue, causing neurological problems like headaches, seizures and even loss of smell. Meningiomas can also occur along the base of the skull beneath the brain; these meningiomas can be challenging to surgically remove because of their location.


Lymphomas grow out of abnormal white blood cells. Most lymphomas grow in other parts of the body and often involve the lymph nodes. There are, however, rare forms that start within the brain. 


Medulloblastomas are caused by a growth of immature cells that normally contribute to the formation of nerve cells in the back lower part of the brain, the cerebellum. Medulloblastomas are the most common aggressive, high-grade brain tumor in children. Different types of medulloblastomas exist, and molecular and pathologic studies can help classify these tumors and predict how well treatments will work.

Pineal Tumors

The pineal gland is a small structure tucked deep within the brain that secretes melatonin, a substance that affects your sleep-wake cycles. These very rare tumors happen most often to children and adults younger than 40. They can cause problems by pressing against other parts of the brain, and they can also block the normal flow of fluid that bathes the brain and spine, causing increased pressure, headaches, nausea and vomiting. Primary pineal tumors range from slow-growing, low-grade (pineocytomas) to fast growing, high-grade (pineoblastomas).

Skull Base Tumors

The skull base refers to the bottom part of your skull, which is where the brain rests. Tumors located at the skull base involve delicate blood vessels, nerves and other structures. If left untreated, skull base tumors can lead to serious consequences, such as blindness or stroke. Types of skull base tumors include:

  • Pituitary tumors: A pituitary tumor is an abnormal growth in the pituitary gland, a small gland located behind your nose. The pituitary gland is the master regulator of other hormone-producing glands throughout the body. Pituitary tumors can disrupt the normal balance of hormones by causing an increase or decrease in hormone production. These tumors can also press against the nearby optic nerves, which triggers vision problems. If a pituitary tumor isn’t causing noticeable symptoms, it may not be discovered until a routine brain imaging or blood test occurs. Learn more about other pituitary disorders.
  • Vestibular schwannoma (acoustic neuroma): Schwannomas grow out of nerve coverings in the head, spine or outer tissues. Within the head, they most commonly grow from the nerve that controls balance (the vestibular nerve). This tumor presses on the inner ear’s hearing and balance nerves; a large tumor may press on a person’s facial nerve or brain structures. Patients may experience hearing loss on one side, ringing in the ears, dizziness, facial numbness, tingling or headaches. Patients with neurofibromatosis type 2, a rare inherited disease, often develop vestibular schwannomas on both sides of their head.
  • Chordomas: Chordomas are a rare form of bone cancer that occurs along the length of the spine, including the base of the skull. Skull-based chordomas commonly affect the nerves that control movement of the face, eyes and swallowing. Symptoms include pain or changes in nerve function, headache, face/neck pain, double vision, facial numbness or paralysis, changes in speech or swallowing problems. 
  • Meningiomas

Learn more about skull base tumor conditions and treatments

Metastatic (Secondary) Brain Tumors

A metastatic brain tumor is cancer that has started elsewhere in the body but spread to the brain. Examples may include lung cancer or breast cancer that has spread to the brain. In adults, brain metastases are actually more common than primary brain tumors. 

Learn more about metastatic brain tumor conditions and treatments.

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