Heather Borders, MD
over 4 years ago
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Diffuse Fibrillary Astrocytoma
Joseph Junewick, MD FACR
|Diagnostic Category: Neoplasia Malignant
|Created: over 7 years ago
|Updated: over 6 years ago
2 year old female with rapidly progressive somnolence and possible seizure.
Diffuse Fibrillary Astrocytoma with Subependymal Extension (Gliomatosis Cerebri)
Pathology – Full mantle biopsy demonstrates diffuse frillary astrocytoma.
MR – Non-enhancing T2 and FLAIR hyperintensity in the right temporal and parietal lobes with subependymal extension.
MRS – Mildly elevated choline and decreased NAA relative to the creatine peaks. A small lactate doublet is also present.
The World Health Organization brain tumor classification scale is: I – benign and circumscribed, II – benign and infiltrative, III – cellular anaplasia, and IV – malignant with endothelial proliferation and hemorrhage/necrosis. Diffuse fibrillary astrocytoma (DFA), an infiltrative tumor composed of astrocytic cells showing nuclear atypia (nucleomegaly, hyperchromasia and pleomorphism), is considered a grade II lesion by the World Health Organization.
Grade II astrocytoma is an uncommon tumor, since at presentation most diffuse astrocytic tumors already show early malignant transformation. Astrocytic differentiation is inferred from nuclear shape (oval to elongate) but differentiation is difficult to determine since cytoplasm is scant in hypocellular tumors and GFAP stains are typically negative. Differentiation is more readily apparent as cellularity increases and pink, glial filament-containing, GFAP immunoreactive cytoplasm becomes apparent. Such cells may be elongate and variably fibrillated (“fibrillary astrocytoma”) or full bodied with abundant eccentric pink cytoplasm (“gemistocytic astrocytoma”). Ki-67 or MIB-1 labeling indices are generally less than 5% . Most tumors are hypocellular. Endothelial proliferation and necrosis are lacking. It is genetically distinct from other lesions and is associated frequently with p53 mutations or occasionally with loss of heterozygosity on chromosome 10p.
Most DFAs occur in young adults, involve the cerebrum rather than cerebellum or spinal cord. In children, age at diagnosis and tumor location, but not histology, have the most significant impact on progression free survival; total resection is the best option with median survival rates usually exceeding 5 years. As a rule, grade 2 tumors lack enhancement on CT and MRI.
Gajjar A, Sanford RA, Heideman R, Jenkins JJ, et al. Low-grade astrocytoma: a decade of experience at St. Jude Children’s Research Hospital. J Clin Oncol (1997); 15:2792-2799.