Pilocytic Astrocytoma

Summary

Pilocytic astrocytomas are brain tumors originating from astrocytes. These are usually infratentorial in the cerebellum, and present as the most common primary brain tumor in children. The tumor consists of a mass of spindle cells with hair-like glial projections. Imaging may also show the presence of pink Rosenthal fibers. It’s important to note that these astrocytomas are different from medulloblastomas in that they can contain both solid as well as cystic components. To diagnose pilocytic astrocytoma, a GFAP stain is commonly performed to see whether the tumor is glial in origin. 

Key Points

• Pilocytic Astrocytoma
  • Characteristics
    • Brain tumor originating from astrocytes
  • Location
    • Usually infratentorial in the posterior fossa (e.g. cerebellum)
  • Presentation
    • Most common primary brain tumor in childhood
  • Diagnosis
    •  Well-circumscribed mass comprised of spindle cells with hair-like glial projections/processes
    • Contains Rosenthal fibers 
    • Contains cystic and solid components
      • Contrast vs. medulloblastoma (another childhood brain tumor) which are almost always solid
    • Stains Glial Fibrillary Acidic Protein (GFAP) positive
  • Treatment/Prognosis
    • Mainstay is surgical resection
    • Usually has a good prognosis