Pilocytic astrocytoma

What it is

Pilocytic astrocytoma is a slow-growing, well-circumscribed (localized) glioma classified as WHO grade 1. It is the most common brain tumor in children and is often curable, particularly when it can be completely removed by surgery.

Understanding Pilocytic astrocytoma

Pilocytic astrocytoma is a benign-behaving, slow-growing tumor that most often arises in the cerebellum but can occur in other locations (such as the optic pathway, hypothalamus, or brainstem). Most carry a KIAA1549::BRAF fusion, which activates the MAPK pathway and predicts a favorable outcome. Because it is circumscribed (unlike diffuse gliomas), it can often be completely removed surgically — and complete removal frequently achieves a cure, with high long-term survival. When the tumor is in a location that prevents complete removal (such as the optic pathway), other treatments — including chemotherapy or MAPK-targeted therapy (MEK inhibitors) — may be used. Pilocytic astrocytoma represents the favorable end of the glioma spectrum. Understanding pilocytic astrocytoma clarifies a common, often curable childhood glioma.

Why it matters

Understanding pilocytic astrocytoma helps families see the favorable end of the glioma spectrum — a slow-growing, often curable childhood tumor, especially when it can be completely removed by surgery.