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Pilocytic astrocytoma

Pilocytic astrocytoma (py-loh-SIT-ik as-troh-sih-TOH-muh) is a slow-growing brain tumor that usually affects children and teens. The term “pilocytic” refers to the cells’ long, hairlike shape as seen under a microscope. The term “astrocytoma” means the tumor starts in star-shaped brain cells called astrocytes.

Pilocytic astrocytoma is a type of brain tumor called glioma, which begins in a glial cell. Glial cells support and protect nerve cells in the brain and help them function properly. Pilocytic astrocytoma grows from a type of glial cell called an astrocyte. Astrocytes help keep the brain working smoothly. They maintain the right conditions around brain cells by managing chemicals, fluids and waste. They also support communication between neurons.

Pilocytic astrocytoma is the most common type of glioma in children. Pilocytic astrocytoma often develops in the part of the brain that controls movement and balance, called the cerebellum. These tumors also can appear in other structures including the optic nerve, brainstem, spinal cord or other parts of the brain.

Most pilocytic astrocytomas are noncancerous, also called benign. Symptoms depend on the tumor’s location but may include headaches, nausea, balance problems, vision changes or behavior changes.

Pilocytic astrocytomas are classified as grade 1 tumors by the World Health Organization (WHO) scale for brain tumors. Grade 1 tumors are considered the least aggressive brain tumors. Grade 1 indicates that the tumor:

  • Grows slowly.
  • Is well defined and has clear borders.
  • Has a low risk of spreading.
  • Often responds well to just surgery without additional treatment.

Pilocytic astrocytomas were previously called juvenile pilocytic astrocytoma (JPA) because the condition is more common in children. Currently, pilocytic astrocytoma is the term used for both adults and children with the condition.

Treatment for pilocytic astrocytoma usually involves surgery to remove the tumor. If the tumor can be completely removed, no other treatment may be needed. When the tumor can’t be fully removed or it grows back, other treatments such as chemotherapy, targeted therapy or radiation may be used.

The prognosis for people with pilocytic astrocytoma is usually very good, especially when the tumor is found early and can be fully removed.

Symptoms of pilocytic astrocytoma can vary depending on the tumor’s size and where it’s growing in the brain. These tumors grow slowly, so symptoms may develop over weeks or months and get worse over time. Many of the signs and symptoms of pilocytic astrocytoma are caused by increased pressure in the brain or by the tumor pressing on nearby structures.

Children with tumors near the cerebellum or brainstem may show signs earlier because those areas control balance, coordination and vital functions.

Pilocytic astrocytoma symptoms in children usually are not different from pilocytic astrocytoma symptoms in adults. The location of the tumor, rather than age, determines the type of symptoms you have.

Physical symptoms of pilocytic astrocytoma

  • Headache, which is often worse in the morning and may change with position.
  • Nausea and vomiting.
  • Problems with balance or coordination.
  • Vision changes, such as blurred or double vision.
  • Weakness in the arms or legs.

Hormone-related symptoms of pilocytic astrocytoma

Pilocytic astrocytoma can cause hormone-related changes that may affect growth or puberty:

  • Hormone changes. If the tumor is near the hypothalamus or pituitary gland, it may disrupt hormone signals, affecting growth or puberty.
  • Delayed or early puberty. Some children may start puberty earlier or later than expected.
  • Slowed growth. Pilocytic astrocytoma tumors around the hypothalamus can lead to slowed growth or failure to grow as expected.

Cognitive and mood-related symptoms of pilocytic astrocytoma

  • Changes in behavior or personality.
  • Difficulty with memory or thinking clearly.
  • Mood swings or emotional changes, such as irritability or sadness, may occur in some people.

Other neurological symptoms of pilocytic astrocytoma

  • Seizures, though these are less common with pilocytic astrocytomas than with other brain tumors.
  • Difficulty with speech or understanding language.
  • New difficulties with movement or coordination, such as clumsiness or stumbling.

The exact cause of pilocytic astrocytomas isn’t known. Most of these tumors happen without a known trigger. However, scientists have found certain factors in genes and the environment that may play a role in the growth of pilocytic astrocytoma tumors.

Many pilocytic astrocytomas are linked to changes in the mitogen-activated protein kinase (MAPK) pathway. This pathway is a system that helps cells communicate and controls how cells grow and divide. These changes can trigger growth signals in brain cells and may lead to tumor growth.

At this time, there’s no proven link between pilocytic astrocytomas and environmental factors such as cellphone use, diet or chemical exposure.

While experts don’t know exactly what causes pilocytic astrocytoma, researchers have found some risk factors that may raise a person’s chances of developing this kind of tumor:

Inherited genetic conditions

  • Neurofibromatosis type 1 (NF1) is the most well-known inherited risk factor. People with NF1 are more likely to develop pilocytic astrocytoma, especially in areas near the eyes and the hypothalamus, deep in the center of the brain.
  • Other rare syndromes, such as Li-Fraumeni syndrome and tuberous sclerosis, also may increase the risk of developing pilocytic astrocytoma.

Age

  • Pilocytic astrocytoma is most common in children and teens.
  • Although rare, adults can develop pilocytic astrocytoma. It may be more aggressive in older people.

Other possible associations

  • Some studies have noted a slightly higher rate of brain tumors, including pilocytic astrocytomas, among farming and petroleum workers, but this link is not well understood.
  • Radiation exposure to the head in childhood, such as during cancer treatment, may raise the risk of some brain tumors.

Pilocytic astrocytoma is usually diagnosed through a combination of methods. Your healthcare professional may start by reviewing your symptoms, giving you a physical exam and taking your medical history. You may have tests, including an imaging test to take pictures of your brain.

 

Radiology for pilocytic astrocytoma usually involves an MRI. The gold standard for diagnosing pilocytic astrocytoma is a brain MRI scan with contrast, which gives a clear picture of the tumor and its features. People who cannot have an MRI scan may have a CT scan instead.

You may have a biopsy to diagnose and grade pilocytic astrocytoma. This test removes a sample of the tumor in a surgical procedure. Then the sample is studied in a lab under a microscope.

Pilocytic astrocytomas are not classified by stages as some tumors are, so staging isn’t part of the of diagnosing these tumors.

Diagnosing pilocytic astrocytoma in adults

In adults, pilocytic astrocytoma is relatively rare and can be harder to recognize because it’s not common. It may be mistaken for a more aggressive tumor. Adults also are less likely to show the classic imaging features that children do.

Diagnosing pilocytic astrocytoma in children

In children, pilocytic astrocytoma often develops in the cerebellum. If symptoms point to a brain tumor, a scan of the brain can quickly help confirm the diagnosis — especially if typical signs show up on MRI, such as a fluid-filled area with a small bump.

Diagnosis can be especially tricky in young children, where early symptoms may be subtle or mistaken for behavioral or developmental issues.

Misdiagnosing pilocytic astrocytoma

Because pilocytic astrocytomas grow slowly and may look similar to other tumors, they are sometimes misdiagnosed. Misdiagnosis is more likely to happen in adults than in children.

Surgery is usually the first and often the only treatment needed for pilocytic astrocytoma, especially when the tumor can be completely removed. Pilocytic astrocytoma tumors usually stay in one area and don’t grow into the healthy brain around them. They usually have clearly defined edges, which makes them easier to remove with surgery.

Sometimes pilocytic astrocytoma tumors grow in areas that are hard to reach, such as near the brainstem, optic nerves or hypothalamus. In these cases, removing the entire tumor could cause damage and affect important brain functions. When that happens, the healthcare team may suggest:

  • Watching and waiting. If what’s left of the tumor isn’t growing or causing problems, you may need to have regular MRI scans to monitor it over time.
  • Chemotherapy. Medicines that stop or slow tumor growth may be used to treat pilocytic astrocytoma. Children may have this treatment instead of radiation if possible.
  • Targeted therapy. If testing shows a genetic change, such as a change in the BRAF gene, newer drugs can be used to block the tumor’s growth signals.
  • Radiation therapy. This may be used if other treatments don’t work, especially in older people. It’s used more carefully in children because it can cause long-term side effects. These can include memory problems, difficulty with attention or learning, and hormone changes that affect growth or puberty.

Even when surgery isn’t possible or the tumor can’t be fully removed, these other treatments often help manage symptoms, improve quality of life, and slow or stop tumor growth.

Potential future treatments

Some pilocytic astrocytomas have a genetic change in a gene called the BRAF gene. The BRAF gene helps control cell growth. When this gene is altered — especially in a form called BRAFV600E — it can cause tumors to grow. Newer drugs called BRAF or MEK inhibitors are designed to block this signal and may help slow or stop tumor growth.

Two of these drugs, dabrafenib (Tafinlar) and trametinib (Mekinist), are approved by the Food and Drug Administration (FDA) for children over age 1 with low-grade gliomas that have a BRAFV600E gene change. Pilocytic astrocytoma is one of the tumor types that may have this altered gene. These medicines are often used together as a combination therapy.

These medicines aren’t usually the first treatment for pilocytic astrocytoma, but they may be considered when surgery isn’t possible or if the tumor grows back.

As researchers continue to study how these tumors grow, targeted drugs may become a more common part of care in the future.

Prognosis and outcomes

The outlook, called prognosis, and survival rates for a pilocytic astrocytoma are usually very good, especially when the tumor can be completely removed with surgery. These tumors grow slowly and usually don’t spread to other parts of the brain or body.

If the entire tumor is removed, most people don’t need any more treatment and remain healthy for years. Sometimes the tumor can return or start growing again. This is called tumor recurrence.

Even when the tumor comes back, it often grows slowly. Other treatments such as chemotherapy, radiation therapy or targeted drugs may help keep it under control.

Age can affect the prognosis. Pilocytic astrocytoma is more common in children, and most children do very well after treatment. The prognosis in children is especially good when the tumor is in the cerebellum and can be completely removed.

In adults, pilocytic astrocytoma tumors are less common and may be harder to diagnose early. They also may behave differently. Sometimes these tumors may come back or be more difficult to treat. Adults also are less likely to show the genetic features that help guide targeted therapy.

Other factors that affect prognosis and outcomes can include:

  • Tumor location. Tumors deep in the brain are harder to remove and more likely to come back.
  • Age at diagnosis. Younger children may have a slightly higher risk of recurrence, even after surgery.
  • Genetic makeup of the tumor. Tumors with certain gene changes, such as the BRAFV600E gene change or the KIAA1549-BRAF fusion (a gene change that causes continuous signals for cells to grow), may respond better to targeted therapies that block these signals.

Most people with pilocytic astrocytomas can live full, active lives with proper treatment and follow-up.

See your usual healthcare professional if you have any signs or symptoms that worry you. If you’re diagnosed with a pilocytic astrocytoma you may be referred to specialists, such as:

  • Doctors who specialize in brain conditions, called neurologists.
  • Doctors who treat cancer with medicine, called medical oncologists.
  • Doctors who use radiation to treat cancer, called radiation oncologists.
  • Doctors who specialize in nervous system cancers, called neuro-oncologists.
  • Surgeons who operate on the brain and nervous system, called neurosurgeons.
  • Rehabilitation specialists.

Brain tumor treatment can be complex. Few hospitals are used to caring for a lot of people with brain tumors. If you don’t feel comfortable with the care at your local facility, consider seeking a second opinion at a more experienced cancer center. Ask your healthcare professional for a referral.

Here’s some information to help you get ready for your appointment.

What you can do

  • Be aware of any pre-appointment restrictions. At the time you make the appointment, be sure to ask if there’s anything you need to do in advance, such as restrict your diet.
  • Write down any symptoms you’ve been experiencing and how long you’ve had them.
  • List your key medical information, including all conditions you have and the names of any medicines you’re taking. Include prescription medicines and medicines you can buy without a prescription. Also list any vitamins or supplements that you take and the doses.
  • Take a family member or friend along. Sometimes it can be difficult to remember all of the information provided to you during an appointment. Someone who goes with you may remember something that you missed or forgot.
  • Write down questions to ask your healthcare professional.

Questions to ask at your first appointment include:

  • What may be causing my symptoms?
  • Are there any other possible causes?
  • What kinds of tests do I need? Do these tests require any special preparation?
  • What do you recommend for the next steps in learning about my diagnosis and treatment?
  • Should I see a specialist?

Questions to ask an oncologist or a neurologist include:

  • What type of brain tumor do I have?
  • Where is my brain tumor located?
  • How large is my pilocytic astrocytoma?
  • How aggressive is my tumor?
  • Is my tumor cancerous?
  • Will I need more tests?
  • What are my treatment options?
  • Can any treatments cure my pilocytic astrocytoma?
  • What are the benefits and risks of each treatment?
  • Is there one treatment you feel is best for me?
  • Is there a clinical trial available to treat my type of tumor? Is it appropriate for me?
  • How will treatment affect my daily activities, such as walking, talking and speaking?
  • Should I see a specialist? What will that cost, and will my insurance cover it?
  • Are there brochures or other printed material that I can take with me? What websites do you recommend?
  • How often should I have checkups?

Note the three questions that are most important to you so you can be sure to get those answered if the time is limited. In addition to the questions that you’ve prepared to ask, don’t hesitate to ask other questions that occur to you.

What to expect from your doctor

Be prepared to answer questions about your symptoms and your health history. Questions may include:

  • What are your symptoms?
  • When did you first notice these symptoms?
  • Have your symptoms gotten worse over time?
  • If you have pain, where does the pain seem to start?
  • Does the pain spread to other parts of your body?
  • Have you participated in any activities that might explain the pain, such as a new exercise or a long stretch of gardening?
  • Have you experienced any weakness or numbness in your legs?
  • Have you had any difficulty walking?
  • Have you had any problems with your bladder or bowel function?
  • Have you been diagnosed with any other medical conditions?
  • Are you currently taking any medicines, including prescription medicines and medicines that you can get without a prescription?
  • Do you have any family history of noncancerous or cancerous tumors?
  1. Childhood astrocytomas, other gliomas, and glioneuronal/neuronal tumors treatment (PDQ) — Health professional version. https://www.cancer.gov/types/brain/hp/child-astrocytoma-glioma-treatment-pdq. Accessed July 16, 2025.
  2. Astrocytoma tumors. American Association of Neurological Surgeons. https://www.aans.org/en/Patients/Neurosurgical-Conditions-and-Treatments/Astrocytoma-Tumors. Accessed July 16, 2025.
  3. Prayson RA, et al., eds. Glial and glioneuronal tumors. In: Neuropathology. 3rd ed. Elsevier; 2023. https://www.clinicalkey.com. Accessed July 11, 2025.
  4. Huang J, et al. Pilocytic astrocytoma. Anesthesia for Oncological Surgery. Springer; 2023. oi.org/10.1007/978-3-031-50977-3_66.
  5. Ferri FF. Pilocytic astrocytoma. In: Ferri’s Clinical Advisor 2026. Elsevier; 2024. https://www.clinicalkey.com. Accessed July 16, 2025.
  6. Louis DN, et al. The 2021 WHO classification of tumors of the central nervous system: A summary. Neuro-Oncology. 2021; doi:10.1093/neuonc/noab106.
  7. Mair MJ, et al. Clinical characteristics and prognostic factors of adult patients with pilocytic astrocytoma. Journal of Neuro-Oncology. 2020; doi: 10.1007/s11060-020-03513-9.
  8. Salles D, et al. Pilocytic astrocytoma: A review of general, clinical, and molecular characteristics. Journal of Child Neurology. 2020; doi: 10.1177/0883073820937225.
  9. Kim JW, et al. Comparison of the clinical features and treatment outcomes of pilocytic astrocytoma in pediatric and adult patients. Child’s Nervous System. 2023; doi:10.1007/s00381-023-05839-x.
  10. Barbato MI, et al. FDA approval summary: Dabrafenib in combination with trametinib for BRAFV600E mutation-positive low-grade glioma. Clinical Cancer Research. 2024; doi:10.1158/1078-0432.CCR-23-1503.
  11. Mikkelsen M, et al. Overview of pediatric low-grade gliomas. https://www.uptodate.com/contents/search. Accessed July 16, 2025.
  12. Pilocytic. National Cancer Institute. https://www.cancer.gov/publications/dictionaries/cancer-terms/def/pilocytic. Accessed July 17, 2025.
  13. Astrocytoma. National Cancer Institute. https://www.cancer.gov/publications/dictionaries/cancer-terms/def/astrocytoma. Accessed July 17, 2025.
  14. Gregory TA, et al. Adult pilocytic astrocytoma in the molecular era: A comprehensive review. CNS Oncology. 2021; doi:10.2217/cns-2020-0027.
  15. Bond KM, et al. Adult pilocytic astrocytoma: An institutional series and systematic literature review for extent of resection and recurrence. World Neurosurgery. 2018; doi:10.1016/j.wneu.2017.11.102.

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