Brain cancer occurs when normal brain cells change into abnormal cells, grow uncontrollably, and invade the surrounding tissue. A mass of abnormal brain cells is called a brain tumor. Tumors can be benign (noncancerous) or malignant (cancerous).

Malignant brain tumors can invade or spread (metastasize) into healthy brain tissue and, rarely, to distant organs within the body. Benign brain tumors do not invade nearby tissues or spread to other parts of the body.

There are two main types of brain tumors. Primary brain tumors originate in the brain. Secondary brain tumors—also called metastatic brain tumors—start in another part of the body and then spread to the brain. An example of a secondary brain tumor is lung cancer that spreads to the brain.

Symptoms of brain cancer depend on factors like the location and type of tumor. They may generally include headaches, seizures, nausea, vomiting, and/or neurological changes. Diagnosis of a brain tumor involves multiple steps, including a physical exam, imaging tests, and a tissue biopsy.

Depending on several factors, including the type, location, and extent of the cancer, treatment may involve surgery, radiation, chemotherapy, or some combination.

Types

There are over 120 different types of tumors that affect the brain and central nervous system (CNS). The World Health Organization (WHO) has classified these tumors by cell type and behavior—least aggressive (benign) to most aggressive (malignant).

Secondary or metastatic brain tumors are four times more common than primary brain tumors.

Primary Brain Tumors

While not an exhaustive list, here are some examples of primary brain tumors. Provided also is a brief description of where in the brain these tumors are generally located and whether they are benign, malignant, or can be both.

  • Glioma: Glioma is a common type of brain tumor derived from glial cells, which support neurons in the brain. Gliomas can be benign or malignant, and there are several types—astrocytomas, brain stem gliomas, ependymomas, oligodendrogliomas, mixed gliomas, and optic pathway gliomas.
  • Astrocytoma: This brain tumor (a type of glioma) can be benign or malignant. Benign astrocytomas may develop in the cerebrum, optic nerve pathways, brain stem, or cerebellum. A malignant astrocytoma called glioblastoma multiforme primarily develops in the cerebral hemispheres.
  • Chordoma: This brain tumor usually occurs at the base of the skull. Even though a chordoma grows slowly, it’s considered malignant because it can spread, often to distant organs like the lungs, liver, or bones.
  • CNS lymphoma: CNS lymphoma is a rare form of non-Hodgkin’s lymphoma that is malignant and often develops in the areas next to the brain ventricles.
  • Ependymoma: This tumor (a type of glioma) is commonly found near the ventricles in the brain. While some ependymomas are slow-growing and benign, others, like anaplastic ependymoma, are fast-growing and malignant.
  • Medulloblastoma: A medulloblastoma is a fast-growing, malignant brain tumor that forms in fetal cells that remain after birth. This tumor is often located in the cerebellum or near the brain stem and occurs more commonly in children but can occur in adults.
  • Meningiomas: Meningiomas grow on the surface of the brain, where the membrane (meninges) that covers the brain is located. Meningiomas can be slow-growing and benign or fast-growing and malignant.
  • Oligodendroglioma: This type of tumor (a glioma) is usually found in the frontal lobe or temporal lobe. It can be benign or malignant.
  • Pineal tumor: Pineal tumors develop in the pineal gland—a small organ located deep within the brain that makes melatonin (a hormone that affects your sleep-wake cycle). This tumor can be benign or malignant.
  • Pituitary tumor: This type of tumor is located on or near the pituitary gland, which is a pea-sized organ located in the center of the brain. Most pituitary tumors are benign.
  • Primitive neuroectodermal tumor (PNET): This is a highly aggressive, malignant tumor typically located in the cerebrum.
  • Rhabdoid tumors: These are highly aggressive, malignant tumors that more often occur in young children than adults. Rhabdoid tumors in the brain tend to be located in the cerebellum or brain stem.
  • Schwannoma: Also known as acoustic neuroma, this tumor is usually benign (rarely malignant) and typically grows around the eighth cranial nerve.

Gliomas are the most common primary brain cancer in adults, accounting for approximately 75% of malignant brain tumors. In children, brain stem glioma, ependymoma, medulloblastoma, pineal tumors, PNET, and rhabdoid tumors are the most common forms.

Metastatic Brain Tumors

Metastatic, or secondary, brain tumors frequently develop as multiple, rather than single, tumors in the brain. In terms of brain distribution, 80% of metastatic brain tumors occur in the cerebral hemispheres, 15% in the cerebellum, and 5% in the brain stem.

Primary brain cancer generally stays within the central nervous system, rarely spreading to distant organs.

Symptoms

With any tumor (benign or malignant), symptoms begin when the tumor grows and causes pressure on the brain tissues. This increased intracranial pressure often first manifests as a headache.

As the pressure on the brain increases, symptoms like nausea, vomiting, blurry vision, personality changes, and drowsiness may develop. In babies, the increased pressure can cause swelling or bulging of their fontanelles (“soft spots”).

Depending on the size and location of the tumor, additional symptoms may occur. Examples of these symptoms based on the affected area within the brain include:

  • Brain stem: Problems swallowing (dysphagia) or speaking, drooping eyelid or double vision (diplopia), or muscle weakness on one side of the face or body
  • Cerebellum: Uncoordinated muscle movements, difficulty walking, dizziness, uncontrolled eye movements, problems swallowing, and changes in speech rhythm
  • Frontal lobe (front of the brain): Changes in personality and behavior, impaired judgment, and thinking and language problems (such as an impaired ability to form words)
  • Occipital lobe (back of the brain): Changes or loss of vision and hallucinations
  • Parietal lobe: Difficulty with speaking, writing, and reading, and problems recognizing objects or navigating spaces
  • Temporal lobe: Impaired short-term and long-term memory, problems speaking and understanding language, and seizures (often associated with unusual smells or sensations)

Causes

In 2020, around 24,000 adults in the United States were estimated to have been newly diagnosed with a brain or spinal cord tumor. A little over 18,000 adults were estimated to have died from such a cancer. Overall, a person’s lifetime risk of developing brain or spinal cord cancer is less than 1%.

Unlike regular headaches, a headache from a brain tumor typically wakes people up at night and worsens over time. Brain tumor headaches also usually intensify when the Valsalva maneuver is performed (in which you pinch your nostril and try to exhale forcefully).

Brain cancer develops when one or more gene mutations (a change in the DNA sequence) causes a normal brain cell to suddenly divide out of control. Without the normal stopgaps that limit a cell’s life—namely apoptosis (programmed cell death)—the cell essentially becomes “immortal,” multiplying out of control.

What precisely causes these gene mutations to occur in the first place is not well understood. Some may be inherited, but the vast majority likely occur randomly.

Primary Brain Cancer

Factors that have been linked to the development of primary brain tumors include:

  • Genetics: Brain tumors are closely linked to mutations of tumor suppressor genes, such as tumor protein 53. They are also common in people with inheritable disorders such as multiple endocrine neoplasia, neurofibromatosis type 2, tuberous sclerosis, Li-Fraumeni syndrome, Turcot syndrome, Von Hippel-Lindau disease, and others.
  • Infections: Epstein-Barr virus (EBV) is closely linked to CNS lymphoma. Cytomegalovirus (CMV) is tangentially linked to glioblastoma in adults and medulloblastoma in children.
  • Environment: Few environmental risk factors are strongly linked to brain cancer other than prior radiation exposure and exposure to vinyl chloride in industrial settings. Cell phones, wireless headphones, and electromagnetic fields have long been suggested as having carcinogenic potential, but there has yet to be solid evidence of this.

Men are generally more likely to get brain cancer than women, although certain types, like meningioma, are more common in women. Similarly, Whites are more likely to get brain cancers in general, but Blacks are more inclined to get meningioma.

Metastatic Brain Tumor

A metastatic brain tumor occurs when cancer cells from another part of the body migrate through the blood-brain barrier—a unique structure comprised of tight junctions that strictly regulates the movement of various materials into the brain.

With brain metastases, the blood-brain barrier is selectively disrupted, allowing for the passage of cancerous cells. The types of cancer that most commonly metastasize to the brain are:

  • Lung
  • Breast
  • Skin (melanoma)
  • Kidney
  • Colon

Diagnosis

Although the signs and symptoms of brain cancer are highly variable, a brain tumor is generally suspected when abnormal neurological symptoms develop and worsen. This is especially true for people diagnosed with advanced cancer.

Primary lung tumors account for 30%–60% of all metastatic brain cancers, and occur in 17%–65% of patients with primary lung cancer.

The procedures and tests used to diagnose brain cancer include the following:

Neurological Examination

If you are experiencing symptoms of a possible brain tumor, your healthcare provider will perform a neurological examination, which consists of testing your muscle strength, balance, level of awareness, response to sensation, and reflexes.

If any of the results of this exam are abnormal, you may be referred to a neurologist or neurosurgeon for further assessment.

Also, if you are having changes in your vision and your healthcare provider suspects a possible brain problem, you may be referred to an ophthalmologist, who can perform a visual field test.

Imaging Studies

Imaging studies provide a way for healthcare providers to visualize the brain tumor and get an idea of its type, based on the tumor’s appearance and location. The main imaging studies used to help diagnose brain cancer are magnetic resonance imaging (MRI) and computed tomography (CT) scans.

Once a tumor is identified, advanced MRI techniques are often used to better understand and evaluate the tumor. These advanced MRI techniques include:

  • Functional MRI (fMRI): This tool measures blood flow and activity within the brain and maps out critical areas of the brain (like those used for speaking and moving).
  • Diffusion tensor imaging (DTI): This tool measures the probable location and orientation of white matter tracts (nerve signaling pathways) in the brain. This information can aid in surgical planning.
  • Magnetic resonance spectroscopy (MRS): This tool compares the biochemical composition of normal brain tissue with brain tumor tissue. It can be used to determine tumor type and aggressiveness.
  • Perfusion MRI: This tool is used to evaluate tumor grade and, specifically, angiogenesis (when the tumor forms new blood vessels to allow for growth).

Positron-emission tomography (PET) may sometimes be used in staging and follow-up.

Biopsy

In most cases, a biopsy, or tissue sample, is needed to render a definitive diagnosis of brain cancer.

The two main types of biopsies used to diagnose brain cancer are:

After the biopsy is taken, it is sent off to a doctor called a pathologist. The pathologist analyzes the sample under a microscope to determine if cancerous cells are present. If so, the pathologist will evaluate the tumor for type and other features, like its behavior, or how quickly it will grow.

  • Stereotactic biopsy: Using a computer, MRI, or CT image and nickel-sized markers placed on different parts of the scalp (to help create a map of the brain), a neurosurgeon makes an incision (cut) into the scalp, then drills a small hole into the skull. A hollow needle is then inserted into the hole to remove a tissue sample of the tumor.Open biopsy (craniotomy): With this type of biopsy, the neurosurgeon performs a craniotomy, which entails removing most or all of the brain tumor. During this operation, small tumor samples are sent off to be immediately examined by the pathologist. Based on the pathologist’s findings, the surgeon may stop or continue with the surgery.

Grading

Because the majority of brain cancers are secondary—as primary brain cancers rarely spread to other parts of the body—brain cancers aren’t staged like other cancers. Rather, brain cancer is graded based on the type of brain cell the cancer arises from and the part of the brain the cancer develops in.

The grade given to a brain tumor describes its seriousness. Typically speaking, the lower the grade of the tumor, the better the outcome for the patient. On the other hand, tumors with a higher grade grow more quickly and aggressively and usually have a poorer prognosis.

Based on the WHO grading system, there are four brain tumor grades:

  • Grade 1 (low-grade): These tumors are slow-growing, rarely spread, and can usually be removed with surgery.
  • Grade 2: These tumors grow slowly and sometimes spread to nearby tissues. They can come back after treatment (called recurrence).
  • Grade 3: These tumors grow rapidly and are likely to spread to nearby brain tissue.
  • Grade 4 (high-grade): These tumors are the most malignant—they grow rapidly and spread easily. They also create blood vessels to help them grow, and they contain areas of dead tissue (necrosis).

Treatment

The treatment of brain cancer depends on the location of the tumor and/or whether the primary brain tumor has metastasized. Here is a brief look at the treatment options.

Surgery

Surgery is the primary and generally most desirable option for treating brain cancer. While surgery most often involves a craniotomy, some smaller pituitary tumors are removed via trans-nasal surgery (through the nasal cavity) or transsphenoidal surgery (through the base of the skull).

In some cases, it’s not always possible to remove the entire brain tumor. The surgeon may then perform a “debulking” surgery, in which the tumor is surgically reduced in size but not completely removed.

Surgery is rarely if ever used for multiple metastatic brain tumors, which are instead treated with radiation and chemotherapy.

In addition to surgical resection, a surgically implanted shunt may be used to relieve acute intracranial pressure.     

Radiation

Radiation therapy is the most common treatment of secondary tumors. There are different types of radiation that may be used. These include:

  • External-beam radiation therapy (EBRT): This type of therapy delivers radiation through the skin to the tumor from a machine outside the body.
  • Whole-brain radiotherapy treatment (WBRT): This type of therapy targets and delivers radiation to the entire brain. It’s used to treat brain metastasis and certain tumors like ependymomas and medulloblastomas.
  • Brachytherapy: This type of therapy, also called internal radiation therapy, entails delivering radioactive material directly into or near the tumor.
  • Proton radiation therapy: This is a type of EBRT that uses protons as the source of radiation (as opposed to X-rays). This type of therapy is a common treatment in children because it reduces the chances of harming growing brain tissue. It’s also used for tumors that are located deep in the skull or near critical brain areas.

Radiation is also used in adjunctive therapy to clear any remaining cancer cells after surgery. This includes standard WBRT as well as stereotactic body radiation therapy (SBRT). SBRT can also be used in the treatment of brain metastases when the number and location of metastases allow it.

If a surgeon decides to resect a brain metastasis, radiation may be used in neoadjuvant therapy to shrink the tumor beforehand.

If a primary tumor is inoperable, radiation therapy can be used in its place, delivered in anywhere from 10 to 20 daily doses. Although remission can be achieved in some cases, this form of treatment is often used for palliative purposes. Additional treatments may be needed to slow disease progression, reduce symptoms, and improve survival.

Chemotherapy

Chemotherapy is a common treatment in adjuvant therapy after surgery, after radiation therapy, or by itself if surgery and radiation are not options. The benefits of chemotherapy can vary since many of the drugs are unable to penetrate the blood-brain barrier. Intrathecal chemotherapy can help by injecting the drugs directly into the fluid-filled space surrounding the brain.

Chemotherapy is generally used for faster-growing brain tumors, like CNS lymphoma, medulloblastoma, and glioblastoma multiforme, and is less useful for many other types.

For some pediatric brain cancers, chemotherapy is the primary approach due to the long-term harm that radiation can cause to a developing brain.

Prognosis

The prognosis of brain cancer varies by the cancer type and grade, and the person’s performance status, which is a measure of how a person can carry on ordinary daily activities while living with cancer and predicts how they may tolerate treatment.

The Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute provides information on cancer statistics. Below is a chart illustrating its data on the five-year relative survival rate for brain cancer based on the following stages:

  • Localized: Cancer is confined to the brain.Regional: Cancer has spread to nearby lymph nodes.Distant: Cancer has metastasized.

A relative survival rate compares people with the same grade of brain cancer to people in the general population. If the five-year relative survival rate for localized brain cancer is 77%, this means that patients with localized brain cancer are about 77% as likely as people without that cancer to be alive five years after being diagnosed.

A Word From Verywell

If you or a loved one has been diagnosed with brain cancer, it’s normal to experience a roller coaster of emotions, including shock, fear, anxiety, anger, confusion, and sadness.

Try to be kind and patient with yourself during this time. Take time to process the diagnosis, talk with loved ones, and ask anything you want of your oncology team—no question is too trivial.

Since no two cases of brain cancer are alike, it’s also important to not get too bogged down with survival rates or other data points. Statistics are based on information from large groups of people and not predictive of any individual case.

Lastly, try to remain hopeful for your care. There are lots of treatment options available—ones that not only target the tumor but also help you feel better by relieving symptoms.

There is even a new class of cancer treatment drugs called immunotherapy drugs. These drugs work by triggering a patient’s own immune system to fight the cancer.

One such drug, Keytruda (pembrolizumab), is currently approved to treat certain patients with advanced brain cancer. It’s also being studied in patients with metastatic brain cancer.

  • Bertolini F, Spallanzani A, Fontana A, Depenni R, Luppi G. Brain metastases: an overview. CNS Oncol. 4(1): 37–46. doi:10.2217/cns.14.51
  • Komori T. The 2016 classification of tumours of the central nervous system: The major points of revision. Neurol Med Chir (Tokyo). 57(7): 301–311. doi:10.2176/nmc.ra.2017-0010
  • National Brain Tumor Society. Tumor Types: Understanding Brain Tumors.
  • Dana-Farber Cancer Institute. Atypical teratoid rhabdoid tumor (ATRT)
  • American Association of Neurological Surgeons. Brain tumors: Types of brain tumors.
  • American Brain Tumor Association. Metastatic brain tumors.
  • Ramakrishna R, Rostomily R. Seed, soil, and beyond: The basic biology of brain metastasis. Surg Neurol Int. 4(Suppl 4): S256–S264. doi:10.4103/2152-7806.111303
  • American Cancer Society. Signs and symptoms of adult brain and spinal cord tumors.
  • National Cancer Institute. Surveillance, Epidemiology, and End Results Program. Cancer stat facts: Brain and other nervous system cancer.
  • Guo C-F, Zhuang Y, Chen Y, Chen S, Peng H, Zhou S. Significance of tumor protein p53 mutation in cellular process and drug selection in brain lower grade (WHO grades II and III) glioma. Biomark Med. 14(12):1139-1150. doi:10.2217/bmm-2020-0331.
  • American Society of Clinical Oncology. Brain tumor: Risk factors.
  • Shannon-Lowe C, Rickinson AB, Bell AI. Epstein—Barr virus-associated lymphomas. Philos Trans R Soc Lond B Biol Sci. 372(1732): 20160271. doi:10.1098/rstb.2016.0271
  • Söderberg-Nauclér C, Johnsen JI. Cytomegalovirus infection in brain tumors. A potential new target for therapy? Oncoimmunology. 1(5): 739–740. doi:10.4161/onci.19441
  • Tiwary S, Morales JE, Kwiatkowski SC, Lang FF, Rao G, McCarty JH. Metastatic brain tumors disrupt the blood-brain barrier and alter lipid metabolism by inhibiting expression of the endothelial cell fatty acid transporter Mfsd2a. Sci Rep. 8(1):8267. doi:10.1038/s41598-018-26636-6
  • Fecci PE, Champion CD, Hoj J, et al. The evolving modern management of brain metastasis. Clin Cancer Res. 25(22):6570-6580. doi:10.1158/1078-0432.CCR-18-1624
  • Fox BD, Cheung VJ, Patel AJ, Suki D, Rao G. Epidemiology of metastatic brain tumors. Neurosurg Clin N Am. 22(1):1-6,v. doi:10.1016/j.nec.2010.08.007
  • Johns Hopkins Medicine. Neurological exam.
  • American Cancer Society. Tests for brain and spinal cord tumors in adults.
  • Dana-Farber Cancer Institute. How we diagnose brain tumors.
  • American Society of Clinical Oncology. Brain tumor: Diagnosis. Updated January 2020.
  • Louis DN, Perry A, Reifenberger G et al. The 2016 World Health Organization classification of tumors of the central nervous system: a summary. Acta Neuropathol. 131(6):803-20. doi:10.1007/s00401-016-1545-1
  • American Cancer Society. Radiation therapy for adult brain and spinal cord tumors.
  • Routman DM, Yan E, Vora S et al. Preoperative stereotactic radiosurgery for brain metastases. Front Neurol. 9: 959. doi:10.3389/fneur.2018.00959
  • Hong N, Joo JN, Shin SH, Gwak HS, Lee SH, Yoo H. The efficacy of postoperative chemotherapy for patients with metastatc brain tumors from non-small cell lung cancer. Brain Tumor Res Treat. 3(2): 108–114. doi:10.14791/btrt.2015.3.2.108
  • Goldberg SB, Schalper KA, Gettinger SN. Pembrolizumab for management of patients with NSCLC and brain metastases: long-term results and biomarker analysis from a non-randomized, open-label, phase 2 trial. Lancet Oncol. 21(5):655-663. doi:10.1016/S1470-2045(20)30111-X

By Colleen Doherty, MD

 Colleen Doherty, MD, is a board-certified internist living with multiple sclerosis.