p Astrocytes Astrocytoma: The most common primary brain tumour. Histological features permit separation into four grades depending on the degree of malignancy. Grading is of limited accuracy and only reflects the features of the biopsy specimen and not necessarily those of the whole tumour. The most malignant type -anaplastic astrocytoma (grade IV) -occurs most frequently and widely infiltrates surrounding tissue. The less common low-grade astrocytomas include the pilocytic (juvenile) type, fibrillary, protoplasmic and gemistocytic types.
- Oligodendro- Oligodendroglioma: Usually a slowly growing, sharply defined tumour, cytes —■ Variants include an anaplastic (malignant) form and a 'mixed' astrocytoma oligodendroglioma.
Composite diagram showing the characteristic features of a malignant astrocytoma.
Vascular Mitosis proliferation ifio
Poor cellular differentiation »|p\v .'-.vff^^: •:■'
Palisading of throughout
Multinucleate giant cell cells around an area of necrosis
Ependymal cells and choroid plexus
[— Ependymoma: Occurs anywhere throughout the ventricular system or spinal canal, but is particularly common in the 4th ventricle and cauda equina. It infiltrates surrounding tissue and may spread throughout the CSF pathways. Variants include an anaplastic type and a subependymoma arising from subependymal astrocytes.
L*- Choroid plexus papilloma: Rare tumours and an uncommon cause of hydrocephalus due to excessive CSF production. They are usually benign but occasionally occur in a malignant form.
Ganglioglioma/gangliocytoma/ncuroblastoma: Rare tumours containing ganglion cells and abnormal neurons. Occur in varying degrees of malignancy.
Pineal cells Pineocytoma/pineoblastoma: Extremely rare tumours. The latter are less well differentiated and show more malignant features.
Poorly — Glioblastoma multiforme: A highly malignant tumour with no cell differentiated differentiation, preventing identification of its tissue origins.
and embryonic —*- Medulloblastoma: A malignant cells tumour of childhood arising from the cerebellar vermis. Small closely packed cells are often arranged in rosettes surrounding abortive axons__________
May seed through the CSF pathways.
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