Pilocytic astrocytoma (grade I)
Pilocytic astrocytoma is a benign brain tumor that arises from astrocytes, the supportive cells in the nervous system.
Normally, astrocytes are responsible for a variety of roles, including providing nutrients to neurons, maintaining the blood-brain barrier, and modulating neurotransmission (how neurons communicate with each other).
These slow-growing tumors usually occur in children, and are considered the most benign type of astrocytoma. Pilocytic astrocytomas can arise anywhere in the central nervous system, but typically develop near the cerebellum, brainstem, hypothalamic region, or optic nerve.
Pilocytic astrocytomas are a specific type of astrocytoma, and also belong to the broader category of gliomas – tumors that arise from glial cells. This is because astrocytes are a type of glial cell. For this reason, pilocytic astrocytomas (grade I) may also be called a “low-grade glioma.”
Some common symptoms of piloctyic astroctyoma include the following:
- Difficulties with balance or walking
- Weight gain or loss
- Premature puberty
Some of these symptoms (headache, fatigue, nausea) can result from increased pressure in the brain. This can occur directly from the growth of the tumor itself, or when the tumor blocks the normal flow of cerebrospinal fluid in the brain. Other symptoms may depend on the size and location of the tumor. For example, some symptoms (weight gain or loss, premature puberty) are specific to tumors that develop in and impact the hypothalamic region.
Gliomas in general are the most common of the pediatric brain tumors.1 Many of these are low-grade astrocytomas, including pilocytic astrocytoma. Pilocytic astrocytomas typically affect patients under the age of 20, accounting for about 15.6% of primary brain tumors in children and adolescents.1
For most patients, the cause of pilocytic astrocytoma is unknown. However, there are a few rare, genetic conditions that may increase a patient’s chance of developing pilocytic astrocytoma. For example, patients with neurofibromatosis type 1 (NF1) may be more likely to develop pilocytic astrocytomas, among other tumors.2
Pilocytic astrocytomas are benign, slow-growing tumors that usually have well-defined boundaries. Because of this, they are often successfully treated with surgery.
However, for reasons that are not clear, pilocytic astrocytomas that arise in the hypothalamus and optic pathways are very infiltrative and cannot usually be removed completely by surgery. In these situations, chemotherapy may be suggested to target any remaining tumor cells. A personalized treatment plan will take into account a variety of factors, including the size and location of the tumor, as well as the patient’s age and general health.
Pilocytic astrocytomas are usually tumors with well-defined boundaries, so if the tumor is accessible, surgery alone may be sufficient treatment. If the tumor can be fully removed, there is low likelihood of recurrence, and cure rates are extremely high. At ten years after diagnosis, the survival rates for pilocytic astrocytoma are 92.2%.1 As these tumors are slow growing, follow up with MRI scans often lasts many years.
- Ostrom, Q.T., et al., CBTRUS Statistical Report: Primary brain and other central nervous system tumors diagnosed in the United States in 2010-2014. Neuro Oncol, 2017. 19(suppl_5): p. v1-v88.
- Rodriguez, F.J., et al., Gliomas in neurofibromatosis type 1: a clinicopathologic study of 100 patients. J Neuropathol Exp Neurol, 2008. 67(3): p. 240-9.