anaplastic astrocytoma (grade 3)
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Introduction
Astrocytoma with anaplasia (Grade 3).
Pathology
- increased cellularity
- nuclear atypia
- mitoses
- tend to progress to glioblastoma
Genetics
- chromosome 9p loss in 50% of anaplastic astrocytomas & GBMs primarily affecting CDKN2A gene
- chromosome 13q loss in 1/3 - 1/2 of high grade astrocytomas RB gene inactivated in 20% of anaplastic astrocytomas, 35% GBMs
- chromosome 12q13-14 amplification in 15% malignant gliomas including gene for CDK4
- allelic loss on chromosome 19q in up to 40% of anaplastic astrocytomas and GBMs
- diminished or absent expression of PHF3
Radiology
- magnetic resonance imaging (MRI)
- computed tomography (CT)
- higher grade astrocytomas show contrast enhancement
Management
- radiation
- prolongs survival
- 5000-6500 cGy
- administered in multiple fractions to an area around the tumor
- radiation necrosis may produce clinical picture indistinguishable from recurrent high-grade tumor
- dexamethasone
- administered with radiation therapy
- tapered to lowest dose after radiation
- chemotherapy (BCNU, CCNU) combined with radiation
- surgery
- surgical excision is not possible because anaplastic astrocytomas infiltrate adjacent brain tissue
- may be useful to reduce mass effect
- stereotaxic radiosurgery with gamma knife
- potential for tumor abalation
- useful for tumors < 3 cm in diameter
- prognosis: 50% survival of 12 months (with radiation)