Pilocytic Astrocytoma

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Pilocytic Astrocytoma

Last updated on Sunday, October 12 2008 by jdmiles

Pilocytic astrocytomas are less common than diffuse astrocytomas, accounting for about 2% of all primary CNS tumors in all age groups. However, they are the most common glioma in children.

They frequently occur in the cerebellum, but can occur in other areas as well. Most optic tract gliomas are pilocytic astrocytomas.

References:

Prayson, R.A., and Goldblum, J.R. (Eds.) (2005). Neuropathology. Elsevier Churchill Livingstone, Philadelphia. (ISBN:0443066582) Page 434.

Related images:

Lobar pilocytic astrocytoma, H&E stain x200
Lobar pilocytic astrocytomas are uncommon, and tend to present in the third and fourth decade of life (which is somewhat older than patients with pilocytic astrocytomas of the cerebellum or third ventricular region).

Lobar pilocytic astrocytoma, H&E stain x40
As is characteristic by all CNS WHO grade 1 tumors, the lobar pilocytic astrocytoma is well demarcated from the surrounding brain parenchyma.

Pilocytic astrocytoma of optic nerve ("Optic Glioma"), Gross Photograph of Resected Specimen.
Despite being a low grade circumscribed tumor, pilocytic astrocytomas can cause significant morbidity when they occur in inopportune locations such as the optic nerve. Optic nerve gliomas may be associated with neurofibromatosis type I, especially when bilateral and when occurring in early childhood.

Pilocytic astrocytoma of optic nerve, with extension into optic nerve sheath, H&E stain x 40
Early studies suggested that pilocytic astrocytomas are of the optic nerve then occurred in association with neurofibromatosis type I or more likely to invade into the optic nerve sheath.

Pilocytic Astrocytoma x20
This low power photomicrographs demonstrates both the biphasic morphology of pilocytic astrocytomas, as well as the tendency of this type of glioma to demonstrate large intratumoral cysts (the cyst wall can be seen in the upper left portion of the photograph).

Pilocytic Astrocytoma x200
Pilocytic astrocytomas are characterized by a biphasic morphology. In this photomicrographs, the solid areas at the center and top of the slide are admixed with microcystic appearing regions.

Pilocytic Astrocytoma x400
Rosenthal fibers, consisting of partially degraded intracytoplasmic accumulation of glial filaments, are characteristically seen within the solid portions of pilocytic astrocytomas. Their irregular globular to elongate shape distinguishes them from displaced red blood cells.

Pilocytic Astrocytoma, H&E stain x 400
Rosenthal fibers can be seen as refractile globular eosinophilic deposits within the solid portions of pilocytic astrocytomas. Ultrastructural examination demonstrates that they occur within the cytoplasm of the neoplastic astrocytes.

Optic Pathway Glioma
Most optic pathway gliomas are pilocytic astrocytomas.

Pilocytic astrocytoma, H&E x 100
The piloid (hair-like) appearance of the astrocytic tumor cells can be appreciated even at low power magnification.

Pilocytic astrocytoma, H&E stain x 200
Both piloid astrocytes (left) and globular Rosenthal fibers (right) can be appreciated at this magnification.

Pilocytic astrocytoma, H&E stain X600
Hair-Like astrocytes and eosinophilic refractile globular Rosenthal fibers (right center).

Pilocytic astrocytoma, intraoperative smear preparation.
Intraoperative smear preparation demonstrates hair-like astrocytes and occasional Rosenthal fibers.