What is pilocytic astrocytoma?

Pilocytic astrocytoma (PA) is a slow-growing type of primary central nervous system (CNS) tumor. A tumor is an abnormal growth of cells. The brain and spinal cord make up the CNS. This means that the tumor starts in the brain or spinal cord rather than starting somewhere else in the body and spreading to the brain.

The term astro or astrocyte comes from the name of the star-shaped cells these tumors start in. Astrocytes are a major type of non-nerve cells in the brain and spinal cord. They support and nourish the CNS. Many different types of tumors start in astrocytes. But PA tumors tend to be among the slowest growing. They’re mostly found in the brains of children and teens. But they can start in any part of the CNS. Adults sometimes have PAs, too.

PAs grow very slowly and rarely invade nearby tissues. Because of this, some healthcare providers consider them to be benign or not cancer. Still, even benign CNS tumors can cause problems as they press on and damage CNS tissue.

What causes PA?

Researchers don’t know what causes PAs. There are also no clear risk factors for these tumors. Research has suggested links between some genetic conditions and higher risk for these tumors. These conditions include:

• Neurofibromatosis types 1 and 2
• Li-Fraumeni syndrome
• Tuberous sclerosis complex
• Nevoid basal cell carcinoma syndrome
• Turcot syndrome

What are the symptoms of PA?

The symptoms of PA depend on where it is in the CNS and how big the tumor is. It may not cause symptoms until it’s big enough to press on nearby brain tissue and cause problems.

PAs most often grow in the cerebellum, the lower back part of the brain. The cerebellum controls balance and coordination. Some PAs grow near and affect the optic nerve and vision. A PA may also block the normal flow of cerebrospinal fluid (CSF). CSF normally fills the cavities of the brain to bathe and cushion the brain and spinal cord. As CSF builds up, it causes increased pressure on the brain (intracranial pressure). This may cause: 

• Seizures that aren’t linked to fever
• Headache 
• Nausea and vomiting 
• Dizziness
• Trouble walking and balance problems 
• Eye problems, like double vision 
• Behavior or personality changes
• Delays in development
• Feeling tired and weak
• Coma

In infants, a PA can cause the soft spots of the head to bulge and the head to grow faster than it should.

Many of these changes can be caused by other medical problems. Still, it’s important to see a healthcare provider if you notice these symptoms. Only a healthcare provider can tell if you have cancer.

How is PA diagnosed?

Healthcare providers will ask about your personal and family health history and recent symptoms. They will do a physical exam and a nervous system exam. For this, the provider will check your coordination and reflexes. They may ask you to do simple things like walk, touch your finger to your nose, or hold your hands out. The provider might use a light to examine your eyes.

You may first see your primary healthcare provider and then get a referral to a: 

• Neurologist, a specialist in diagnosing and treating diseases of the brain and spinal cord 
• Neurosurgeon, a specialist who does brain or spinal cord surgery 
• Neuro-oncologist, a specialist in brain and spinal cord cancers 

If a brain tumor is suspected, you will need imaging scans of your brain. Some of the tests and procedures needed include:  

• MRI. MRIs use radio waves, magnets, and a computer to make detailed images of the inside of your body. For this test, you lie still on a narrow table as it passes through a long, tube-like scanner. If you’re not comfortable in small spaces, you may be given medicine to help you relax for the test. A needle may be used to put contrast dye into your blood for this test. It helps outline the structures in your head so they show up more clearly on the scans. MRI is the best test to look for CNS tumors.
• CTscan. A CT scan uses a series of X-rays and a computer to create detailed images of the inside of your body. For this test, you lie still on a table as it slowly slides through the center of the ring-shaped CT scanner. The scanner directs a beam of X-rays at your body. A dye might be put into your blood to help get clearer images.
• Biopsy. A biopsy might be the only sure way to know what kind of tumor it is. But sometimes a PA can be diagnosed based on how it looks on imaging tests. In a biopsy, a tiny piece of the tumor is taken out and tested in a lab. To take a sample, a surgeon makes a small hole in the skull and inserts a hollow needle into the brain. Imaging tests are used to help guide the needle to the tumor. A syringe is then used to take out a tiny piece of it. A biopsy might also be done as part of surgery to take out the tumor.

The tissue removed during a biopsy is sent to a lab for testing. Part of the testing includes finding the tumor’s grade. The grade tells how different the tumor cells are from normal cells and how fast they’re likely going to grow and spread.

Astrocytomas are graded on a scale from 1 to 4, based on how abnormal the cells look and how fast the tumor is likely to grow and invade other tissues. Roman numerals I (1), II (2), III (3), and IV (4) are used. The cells from a grade I (low-grade) tumor have well-defined borders and look almost normal under a microscope, grow slowly, and rarely spread to other parts of the CNS. Cells from a grade IV tumor look very different, grow very quickly, and are likely to spread to other parts of the CNS. 

How is PA treated?

Any tumor in the brain may cause problems by pressing against brain tissue. The standard treatment for PA is surgery to remove the tumor, when possible. If all of the tumor is removed, the outlook is usually good.

If the tumor is in a spot where it can’t be fully removed during surgery, adults and older children might get radiation therapy to help kill any tumor cells left in the area. Sometimes chemotherapy and/or targeted therapy are used. 

In younger children, chemotherapy might be recommended after surgery, but radiotherapy is rarely used. This is because radiation can cause long-term growth and development problems in young children.

Because PAs grow very slowly, your healthcare provider may want to watch first to see if the tumor comes back after surgery. This is because the risks of the radiation therapy may outweigh the risk of the PA growing back. This can be done for adults and children.

In some cases, a PA may block drainage of the CSF from your brain. This, causes CSF to build up in the brain. If this happens, you may need surgery to put a tube called a shunt in to drain excess CSF. After the tumor is removed, CSF can drain the way it should, this problem goes away, and the shunt is removed.

Your medical team will talk with you about the best treatment plan for your tumor. After treatment, you’ll need ongoing follow-up with your healthcare provider. This may include repeated imaging scans to check for signs that the tumor has come back. It’s very important to keep follow-up appointments so that your medical team can watch for any changes. 

What are possible complications of PA?

Overall, the outcome is good for most people with PA tumors. Rarely, they might come back after treatment and need to be treated again.

Key points about pilocytic astrocytoma

• PA is a type of central nervous system (CNS) tumor. It starts in the star-shaped astrocyte cells in your brain.
• These tumors tend to be very slow growing and rarely spread.  
• They most often occur in children and teens, but sometimes happen in adults.
• The usual treatment for PA is surgery to remove the tumor, if possible. 
• People with these tumors tend to have a good outcome after treatment. 
• It’s very important to follow up with your medical team to continue to watch for any changes after treatment.