Astrocytoma

Astrocytoma is a type of brain tumour originating from astrocytes, star-shaped glial cells in the cerebrum. These tumours typically remain confined to the brain and spinal cord, rarely affecting other organs.

Astrocytomas are the second most common type of glioma after glioblastomas and can occur in various parts of the central nervous system.

Two PET images—the upper of which shows a normal brain and the lower shows astrocytoma

Pathophysiology

Astrocytomas cause regional effects through compression, invasion, and destruction of brain tissue, leading to hypoxia, competition for nutrients, and the release of metabolic by-products and cytokines. These processes can disrupt normal brain function and elevate intracranial pressure due to mass effect, increased blood volume, or cerebrospinal fluid accumulation.

Genetic and Molecular Alterations

High-grade astrocytomas often exhibit homozygous deletion of CDKN2A/B. A genome-wide pattern of DNA copy-number alterations (CNAs) has been identified, correlating with patient survival and treatment response. This pattern can distinguish a subtype of lower-grade astrocytoma with a one-year survival phenotype.

Diagnosis

Diagnosis begins with a history of symptoms and a basic neurological exam, including vision, balance, coordination, and mental status tests. CT and MRI scans are essential for characterising tumour size, location, and consistency. Histologic analysis through biopsy is required for grading. The MRI or CT scans might be enhanced with a contrast dye for better tumour visualisation.

Low-grade astrocytoma of the midbrain (lamina tecti), sagittal T1-weighted magnetic resonance imaging after contrast medium administration

A pathological specimen of a gemistocytic astrocytoma

MRI scans of an astrocytoma patient, showing tumour progression over the course of seven years

Grading

The World Health Organisation (WHO) grading system categorises astrocytomas from grade I to IV based on characteristics like atypia, mitosis, endothelial proliferation, and necrosis.

• Grade I: Includes pilocytic astrocytoma, subependymal giant cell astrocytoma, and subependymoma. These are slow-growing, benign tumours often associated with long-term survival.
• Grade II: Includes low-grade (fibrillary) astrocytoma, pleomorphic xanthoastrocytoma, and mixed oligoastrocytoma. These are relatively slow-growing but can evolve into higher-grade tumours.
• Grade III: Anaplastic astrocytomas, often linked to seizures and neurologic deficits. Standard treatment involves surgical removal followed by radiation.
• Grade IV: High-grade astrocytomas, typically glioblastomas, are extremely infiltrative and have poor prognosis despite aggressive treatment.

Prevention

There are no precise guidelines for preventing astrocytoma as the exact cause is unknown.

Treatment

Society and Culture

Notable Cases

• Lee Atwater: U.S. Republican strategist diagnosed with astrocytoma in 1990, died in 1991.
• Ted Kennedy: U.S. Senator who died of malignant glioma.
• Charles Whitman: Diagnosed post-mortem with astrocytoma after a mass murder event in 1966.
• Dan Quisenberry: Major League pitcher diagnosed with grade IV astrocytoma in 1998, died the same year.
• Richard Burns: 2001 World Rally Champion, diagnosed in 2003, died in 2005.
• Matt Cappotelli: Professional wrestler diagnosed with grade 2/3 astrocytoma in 2005, died in 2018.

Self-assessment MCQs (single best answer)

What type of glial cell do astrocytomas originate from?

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Which imaging technique is essential for characterising the size, location, and consistency of an astrocytoma?

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What is the typical effect of high-grade astrocytomas on CDKN2A/B?

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Which World Health Organisation (WHO) grade of astrocytoma is characterised by being slow-growing and often associated with long-term survival?

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Which diagnostic procedure is essential for grading an astrocytoma?

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What is a common treatment approach for low-grade astrocytomas to achieve long-term functional survival?

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Which notable individual was diagnosed post-mortem with astrocytoma after a mass murder event in 1966?

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What is a characteristic feature of grade IV astrocytomas?

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What is a common symptom linked to anaplastic astrocytomas (Grade III)?

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What is a significant challenge in treating high-grade astrocytomas?

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