Pilocytic Astrocytoma

Pilocytic Astrocytoma is a type of brain tumor that primarily affects the central nervous system, especially in children and young adults. It arises from astrocytes, which are star-shaped cells that support nerve cells in the brain. This tumor is generally slow-growing and considered benign, meaning it is less likely to spread aggressively. Symptoms often result from pressure on nearby brain structures, causing headaches, balance problems, or vision changes. Diagnosis usually involves imaging studies like MRI to identify the tumor's location and size. Treatment often includes surgery to remove the tumor, which can lead to good outcomes. Understanding this condition helps explain how brain tumors can impact neurological function.

Pilocytic Astrocytoma is a WHO grade I glioma characterized by a well-circumscribed, slow-growing neoplasm derived from astrocytes. It most commonly occurs in the cerebellum but can also arise in the optic pathways, brainstem, and cerebral hemispheres. The tumor is associated with a BRAF gene alteration, often a fusion involving KIAA1549-BRAF, leading to constitutive activation of the MAPK pathway. Histologically, it shows biphasic patterns with compacted bipolar cells and loose microcystic areas, along with Rosenthal fibers and eosinophilic granular bodies. Clinically, it presents with symptoms related to mass effect or increased intracranial pressure. Despite its neoplastic nature, it has a favorable prognosis due to its low proliferative index and responsiveness to surgical resection. It is a major differential diagnosis in pediatric brain tumors.