Pilocytic Astrocytoma

Most common infratentorial neoplasm in pediatrics. It is benign.

=Presentation=

Presents with non-acutely.

Epidemiology
=Mechanisms=

=Diagnosis=

Pathology
A well circumscribed lesion with predilection for the cerebellum, hypothalamus, third ventricle, optic nerve, cerebral hemisphere, and spinal cord. When occuring in the hypothalamus, optic chiasm, or third ventricle there may be association with neurofibromatosis.

Microscopic
Bipolar cells with bland, oval, elongated nuclei and long piloid processes

Rosenthal fibers

Eosinophilic granular bodies

Bizarre or multinucleated cells (pennies on a plate nuclei arrangement)

Can see oligodendroglioma-like regions

Differential Diagnosis

 * 1) Pilocytic gliosis
 * 2) Ganglioglioma
 * 3) Pleomorphic xanthoastrocytoma
 * 4) Fibrillary astrocytoma
 * 5) Oligodendroglioma

Radiology
The solid portion of the pilocytic astrocytoma enhances strongly.

Well demarcated

Will be hypointense on T1 and hyperintense on T2. The cystic component will be similar to CSF on T1 and T2 but can be hyperintense on proton density weighted imaging or FLAIR.

On PET, it will show avid uptake, unique to a low-grade tumor.

Partially cystic with mural nodule, (differential includes: hemangioblastoma)

Anaplasia is less common when the lesion is cystic compared to solid.

Typically, in the pediatric patient the lesion will be cystic (60-80%).

=Treatment=

Excellent prognosis (80% 2-year survival)

Rarely becomes an advanced process