Pilocytic Astrocytoma: Causes and Risk Factors

The underlying cause of pilocytic astrocytoma (PA), a rare tumor of the brain or spinal cord, is unknown. It is most common in children and young adults, and in people with genetic disorders such as neurofibromatosis, Li-Fraumeni syndrome, and tuberous sclerosis.

This article will examine the causes and risk factors of PA.

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Common Risk Factors

A risk factor is something associated with the development of a disease such as cancer, but not necessarily causing that disease. People with a risk factor for developing PA will not necessarily develop one.

Some risk factors for PA include:

Age: PA is more common in children and young adults than in older adults, although it can occur at any age.
Exposure to radiation: Therapeutic radiation (such as radiation to the head to treat cancer) is associated with a higher risk of developing a tumor in the brain over time. The average time between radiation therapy for cancer and the subsequent development of secondary cancer is usually 10-15 years.
Prenatal Factors: Prenatal birth weight, especially a high fetal growth rate, has been associated with an increased risk of PA. The reason for this finding is not certain, but researchers believe that conditions such as gestational diabetes (diabetes related to pregnancy) may play a role.


Rarely, children have inherited abnormal genes from a parent that put them at increased risk for certain types of brain and spinal cord tumors such as PA. In other cases, these abnormal genes are not inherited, but occur as a result of changes (mutations) in the gene before birth.

People with hereditary tumor syndromes often have tumors that start when they are young. Some of the better known syndromes are:

Neurofibromatosis type 1: This is the most common syndrome associated with tumors in the brain or spinal cord. It is often inherited from a parent, but it can also start in some children whose parents don’t have it. Changes in the NF1 gene cause this condition. PA occurs in approximately 15% of patients with neurofibromatosis type 1.
Neurofibromatosis type 2: This condition is less common than neurofibromatosis type 1. It can also be inherited or start in children with no family history. Changes in the NF2 gene are almost always responsible for neurofibromatosis type 2.
Tuberous Sclerosis: Also known as tuberous sclerosis complex, this is a rare genetic disease that causes benign (non-cancerous) tumors to grow in various organ systems, including the brain, kidneys, heart, lungs, eyes, liver, pancreas, and skin. This condition is caused by changes in the TSC1 or TSC2 gene.
Li-Fraumeni syndrome: People with this syndrome have an increased risk of PA, as well as breast cancer, soft tissue sarcomas, leukemia, and some other cancers. It is caused by changes in the TP53 gene.
Turcot syndrome: Turcot syndrome is a rare condition characterized by the development of a brain tumor, with secondary tumors in the colon.

Lifestyle Risk Factors

Lifestyle-related risk factors such as diet, body weight, physical activity and tobacco use play an important role in many cancers in adults. But it usually takes years for these factors to increase the risk of cancer, and they’re not thought to play a major role in childhood cancers, including brain tumors like PA.

At this time, there is no known way to prevent or reduce the risk of pilocytic astrocytoma in your child.


Researchers are still studying the causes and risk factors associated with pilocytic astrocytoma, but it is thought that certain genetic conditions may play a role. Previous irradiation of the head from radiation therapy for cancer may have an effect.

A word from Verywell

Most PA cases are spontaneous and not associated with known risk factors. In addition, many of the known risk factors for PA cannot be prevented, such as inherited genetic disorders. There is a small risk of brain tumors in patients who have had radiation to the head before, and health care providers will consider this before ordering radiation therapy in children.

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