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diffuse astrocytoma (WHO grade 2)
Grade 2, most commonly fibrillary astrocytoma.
Epidemiology:
1) 18% of primary brain tumors
2) most common in late middle age
Pathology:
-> marked tendency to become more anaplastic with time
-> a tumor initially diagnosed as a diffuse astrocytoma frequently proves on later biopsy to be anaplastic astrocytoma or glioblastoma
Microscopic Pathology:
- well differentiated neoplastic astrocytes on a background of loosely structured sometimes microcystic tumor matrix
- moderately increased cellularity
- occasional nuclear atypia
- mitotic activity generally absent; single mitosis does not increase grade
- no necrosis or vascular proliferation
- fibrillary astrocytoma: most common
- gemistocytic astrocytoma
- protoplasmic astrocytoma:
Immunohistochemistry:
- GFAP +
- vimentin +
- S100 +
- Ki67/MIB1 usually < 4%; <1% for protoplasmic variant
Genetics:
- Ras mediated signal transduction involved in initiation of astrocytoma development however ras mutations have not been identified
- PDGF/PDGFR expression elevated in every grade of astrocytic neoplasm
Management:
1) surgical excision
a) should be performed if feasible
b) may relieve symptoms
2) post-operative radiation therapy (indications uncertain)
3) no role for chemotherapy
4) prognosis: 93 months
Also see further descriptions under astrocytic neoplasm and subtypes.
Specific
fibrillary astrocytoma
gemistocytic astrocytoma
protoplasmic astrocytoma
General
astrocytoma (astrocytic neoplasm)
Figures/Diagrams
Astrocytic neoplasms
References
- Zhu & Parada. Nature Reviews Cancer 2:616-26, 2002