Astrocytomas are typically described as low grade astrocytomas (LGAs) or high grade astrocytomas (HGAs) based on pathological characteristics.
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
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:
|
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
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 is present |
Prognosis |
High incidence of progression to glioblastoma |
Very poor prognosis |
External Link:
Overview of Astrocytomas at the Atlas of Genetics and Cytogenetics in Haematology and Oncology
