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CNS tumor

Diffuse astrocytoma - fibrillary

Reviewers: Eman Abdelzaher, M.D., Ph.D. (see Reviewers page)
Revised: 29 February 2012, last major update February 2012
Copyright: (c) 2005-2012, PathologyOutlines.com, Inc.


● The most frequent variant of diffuse astrocytoma

Micro description (Histopathology)

● Fibrillary astrocytes with naked, atypical, elongated, irregular, hyperchromatic nuclei embedded in a fibrillary background
● Microcysts are common
● Some gemistocytes may be admixed

Micro images

The processes of these star-shaped cells form a felt-like perivascular mantle

All astrocytomas have a tendency, as in this case, to appear microcystic

Well differentiated tumor is HAM56 negative (no macrophages)

Cytology images

Smear shows neoplastic astrocytes with cytoplasmic glial processes and variable nuclear atypia

Positive stains


Differential diagnosis

Gliosis: hypertrophy of cells rather than hyperplasia, even distribution
Oligodendroglioma grade II: uniformly rounded nuclei with small distinct nucleoli, perinuclear halos, chicken wire vessels, calcification, GFAP negative

End of CNS tumor > Diffuse astrocytoma - fibrillary

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