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Pilocytic Astrocytoma
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Pilocytic Astrocytoma

Overview
  • Circumscribed, slow-growing, typically cystic, Grade 1 astrocytic tumor.
Clinical Highlights
  • Most frequent pediatric CNS tumor (rarely occurs in adults).
    • Typically occurs in 1st or 2nd decade of life.
  • Most common locations:
    • Posterior fossa (cerebellum and brainstem): obstructive hydrocephalus, commonly cystic w/mural nodule.
    • Hypothalamus: Endocrinopathy, typically solid mass.
    • Optic pathway (optic nerve/optic chiasm, "optic nerve glioma"): Vision loss & diplopia, these are sometimes associated w/NF-1
  • Less common locations:
    • Spinal cord: Myeloradiculopathies
    • Cerebrum
    • Thalamus/Basal ganglia
Radiographic Highlights
  • Cyst with a mural nodule (cerebellum/cerebrum)
    • Solid mass with strong contrast enhancement along the wall of the cyst (cyst, itself, may or may not enhance).
  • Circumscribed-mass (hypothalamus)
  • Dorsal, exophytic mass (brainstem)
    • brainstem gliomas grow outward (exophytic) beyond their surface of origin along the dorsal (posterior) aspect of the brainstem.
Pathology
  • Circumscribed, cystic, with biphasic: compact/loose cellular architecture.
    • Compact architecture: bipolar, elongated cells with bland spindle nuclei; Rosenthal fibers (bright, eosinophilic, beaded, elongated, or corkscrew-shaped intracytoplasmic inclusions); eosinophilic granular bodies (EGBs), hyaline droplets.
    • Loose (microcystic) architecture: Microcystic with myxoid material and delicate cellular processes.
  • Tumor name comes from its hair-like (piloid) processes.
Pilomyxoid Astrocytoma
  • Myxoid variant of pilocytic astrocytoma that is generally more aggressive (grade 2), has a predilection for the sellar region, and lacks Rosenthal fibers and eosiniphilic granular bodies on histopathology.
Genetics
  • Typically sporadic but can be associated with NF-1, especially the optic nerve gliomas.
References
  • Adesina, Adekunle M., Tarik Tihan, Christine E. Fuller, and Tina Young Poussaint. Atlas of Pediatric Brain Tumors. Springer, 2016.
  • Daroff, Robert B., Joseph Jankovic, John C. Mazziotta, and Scott L. Pomeroy. Bradley’s Neurology in Clinical Practice E-Book. Elsevier Health Sciences, 2015.
  • Louis, David N., Arie Perry, Guido Reifenberger, Andreas von Deimling, Dominique Figarella-Branger, Webster K. Cavenee, Hiroko Ohgaki, Otmar D. Wiestler, Paul Kleihues, and David W. Ellison. “The 2016 World Health Organization Classification of Tumors of the Central Nervous System: A Summary.” Acta Neuropathologica 131, no. 6 (June 1, 2016): 803–20. https://doi.org/10.1007/s00401-016-1545-1.
  • Marvin 101. English: Histopathology of Rosenthal-Fibres. H&E Staining Showing These Elongated Eosinophilic Structures in a Case of Pilocytic Astrocytoma. Magnification 400x. January 22, 2009. Own work. https://commons.wikimedia.org/wiki/File:Rosenthal_HE_40x.jpg.
  • Newton, Herbert B. Handbook of Brain Tumor Chemotherapy, Molecular Therapeutics, and Immunotherapy. Academic Press, 2018.
  • Orkin, Stuart H., David E. Fisher, A. Thomas Look, Samuel Lux, David Ginsburg, and David G. Nathan. Oncology of Infancy and Childhood E-Book. Elsevier Health Sciences, 2009.
  • Perry, Arie. “WHO’s Arrived in 2016! An Updated Weather Forecast for Integrated Brain Tumor Diagnosis.” Brain Tumor Pathology 33, no. 3 (July 1, 2016): 157–60. https://doi.org/10.1007/s10014-016-0266-4.
  • Prayson, Richard A., and Mark L. Cohen. Practical Differential Diagnosis in Surgical Neuropathology. Springer Science & Business Media, 2000.
  • Reni, Michele, Elena Mazza, Silvia Zanon, Gemma Gatta, and Charles J. Vecht. “Central Nervous System Gliomas.” Critical Reviews in Oncology/Hematology 113 (May 2017): 213–34. https://doi.org/10.1016/j.critrevonc.2017.03.021.
Ryall, Scott, Uri Tabori, and Cynthia Hawkins. “A Comprehensive Review of Paediatric Low-Grade Diffuse Glioma: Pathology, Molecular Genetics and Treatment.” Brain Tumor Pathology 34, no. 2 (April 1, 2017): 51–61. https://doi.org/10.1007/s10014-017-0282-z.
  • Sharma, Suash, and Prabal Deb. “Intraoperative Neurocytology of Primary Central Nervous System Neoplasia: A Simplified and Practical Diagnostic Approach.” Journal of Cytology / Indian Academy of Cytologists 28, no. 4 (2011): 147–58. https://doi.org/10.4103/0970-9371.86339.
  • Wippold, F. J., A. Perry, and J. Lennerz. “Neuropathology for the Neuroradiologist: Rosenthal Fibers.” American Journal of Neuroradiology 27, no. 5 (May 1, 2006): 958–61.
Image References
  • Rosenthal Fibers and Eosiniphilic Granular Body
    • CNS: PILOCYTIC ASTROCYTOMA. The Armed Forces Institute of Pathology Electronic Fascicles (CD-ROM Version of the Atlas of Tumor Pathology).

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