Pilocytic Astrocytoma

Pilocytic astrocytoma, previously referred to as cystic cerebellar astrocytoma or juvenile pilocytic astrocytoma, was first described in 1931 by Harvey Cushing based on a case series of cerebellar astrocytomas. Pilocytic astrocytomas are low-grade, usually benign, slow-growing, well-circumscribed brain tumors that tend to occur in the pediatric population and also young adults. This condition arises from astrocytes—the star-shaped cells that support nerve cells in the brain. According to the World Health Organization (WHO) classification of central nervous system (CNS) tumors, pilocytic astrocytomas are grade I gliomas with a generally good prognosis. While pilocytic astrocytomas most often occur in the cerebellum, they can also be found along the optic pathways, hypothalamus, and brainstem. These tumors may also occur in the cerebral hemispheres, though this is more common in young adults. The presentation and treatments for pilocytic astrocytomas vary based on their location; however, this article will focus on cerebellar pilocytic astrocytomas. According to the new 2021 WHO classification of CNS tumors, pilocytic astrocytomas are grouped with other circumscribed astrocytic gliomas, such as pleomorphic xanthoastrocytoma, subependymal giant cell astrocytoma, and choroid gliomas.