Astrocytomas are typically described as low or high grade based on pathological characteristics (see pathology).
Low Grade Astrocytomas (LGA)
Localized
Grow slowly over a long period of time
Most LGA are of two types:
1. Pilocytic astrocytoma (PA)
- World Health Organization [WHO] grade I
- circumscribed
- homogeneously neoplastic
- low potential for tissue infiltration or malignant degeneration
- lacks p53 changes, but may show loss of chromosome 17q in the region of
the NF1 gene
2. Diffuse fibrillary astrocytoma (DA)
- WHO grade II
- invasive tumor
- tendency to undergo malignant change (esp in adults)
- Genetically distinct - associated frequently with p53 mutations or occasionally
with loss of heterozygosity on chromosome 10p.
Other Low-Grade Astrocytomas:
- Pleomorphic Xanthoastrocytoma (PXA)
- form of astrocytoma unique to children
- more common in late childhood and early adolescence
- Subependymal Giant Cell Astrocytoma
- Dysembryoplastic Neuroepithelial Tumor (DNET)
- some would argue that these are neuroepithelial tumors rather than gliomas
- Ganglioglioma
- Oligodendroglioma
- Desmoplastic infantile ganglioglioma
Table: Characteristics of Low-Grade Astrocytomas
|
Juvenile Pilocytic Astrocytoma(JPA) |
Desmoplastic Cerebral Astrocytoma |
Subependymal Giant Cell Astrocytoma |
Fibrillary [P1] |
Most Common Patient Age |
Early childhood |
Usually <2 years (infantile) |
Early childhood, may be as early as neonatal period |
30-40yrs |
Most Common Tumor Location |
Cerebellum |
Cerebral hemispheres |
Subependymal origin Occur along lining of lateral ventricles |
Brain parenchyma May be supratentorial |
Growth |
Limited Indolent nature |
Invade leptomeninges |
Grows to invade 4th ventricle May obstruct foramen of Munro |
Diffuse infiltration of parenchyma Anaplastic progression |
Histology |
Well-circumscribed Solid and cystic architectural pattern Rosenthal fibers Commonly has vascular proliferation |
Highly spindled cells Collagen GFAP-reactive |
Both glial and neuronal nature suggested -reactive with both types of tumor markers -lineage still debated Large cells with abundant cytoplasm Occasional calcification Fibrillary pattern may be seen |
Nuclei of normal astrocytes, but may be pleomorphic No mitotic figures No vascular proliferation No necrosis |
Special Features |
Unique to children |
Their association with basal lamina may be responsible for their indolent nature Extracellular matrix proteins inhibit cell growth |
Associated with tuberous sclerosis[P2] |
Lack contrast enhancement |
Prognosis |
Very good: -Indolent nature - Long term prognosis related to location |
Favorable, even with large size |
Total resection is the best option for progression-free survival |
High-grade astrocytomas
- Worse prognosis than LGA
- Higher rate of neuraxis dissemination
- Grow rapidly
- Two main classes of high grade astrocytomas:
- anaplastic astrocytomas
- glioblastoma multiforme
Table : Characteristics of High Grade Astrocytomas
|
Anaplastic Astrocytoma |
Glioblastoma Multiforme (GBM) |
Patient Age |
Uncommon in children Tend to occur in adults (median age 40yrs) |
Uncommon in children Tend to occur in adults (median age 45-70yrs). |
Tumor Location |
Cerebral hemispheres Brain stem |
Subcortical white matter of cerebral hemispheres |
Histology |
Increase in cellularity Nuclear pleomorphism Hyperchromasia May have mitosis & vascular proliferation No necrosis
|
Dense cellularity Mitotic figures Vascular proliferation Necrosis |
Prognosis |
High incidence of progression to glioblastoma |
Very poor prognosis |
