Fibrillary astrocytoma (historical)

Last revised by Frank Gaillard on 28 Sep 2021

Fibrillary astrocytoma is a historical term for the most common histological appearance of diffuse astrocytoma. The term was removed from the updated 4th edition (2016) of the WHO classification of CNS tumors and no longer exists as a distinct entity, although the term "fibrillary" continues to be used in histological descriptions 6


Fibrillary astrocytomas are predominantly composed of a tumor matrix rich with neuroglial fibrils, which give the tumor its name and firm consistency 4. Within the tumor matrix are embedded neoplastic fibrillary astrocytes with mild nuclear atypia (enlarged, irregular contour, hyperchromasia and coarsened nuclear chromatin pattern) and a low cellular density 2-3. The nuclei are elongated and appear "naked" 4

Often microcystic spaces containing mucinous fluid are present 2,5. Like all tumors derived from astrocytes, fibrillary astrocytomas stain with glial fibrillary acidic protein (gFAP) 2-3

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Cases and figures

  • Case 1: FLAIR
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  • Case 2: T1
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  • Case 3: T2
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  • Case 4: FLAIR
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