Tumours Of The Cerebral Hemispheres Intrinsic

Intrinsic tumours arise within the brain substance. ASTROCYTOMA (and glioblastoma multiforme)

Astrocytomas may occur in any age group, but are commonest between 40 and 60 years. Malc:female = 2:1

Primary sites: Found in equal incidence throughout the frontal, temporal, parietal and thalamic regions, but less often in the occipital lobe. Microscopic classification defines 4 grades (Kcrnohan I-IV), but this is of limited accuracy. A more practical description for the clinician divides tumours into either 'malignant' or 'low grade'.

'Malignant' astrocytoma/glioblastoma multiforme

Malignant astrocytoma (grade III/IV) and glioblastoma multiforme (grade IV) constitute over 40% of all primary intracranial turn ours. Peak age incidence is 55 years. These tumours widely infiltrate adjacent brain; growth is rapid. At autopsy, microscopic examination usually reveals spread to multiple distant sites.

MALIGNANT ASTROCYTOMA

Overlying -gyi flattened and pale

Necrotic areas may coalesce and form cystic cavities

'Low grade' astrocytoma

Low grade astrocytomas (grade I/I I) make up 14% of all primary intracranial tumours and occur on average at an earlier age than their malignant counterparts (about 40 years).

Overlying -gyi flattened and pale

Necrotic areas may coalesce and form cystic cavities

At autopsy 75% show microscopic spread to the contralateral hemisphere. Some patients may present with a bilateral corpus callosal tumour or v'butterfly' astrocytoma

FIBRILLARY ASTROCYTOMA

FIBRILLARY ASTROCYTOMA

, Firm, rubbery texture with or without cystic regions

Infiltrates surrounding brain with minimal mass effect and neuronal damage

These tumours are diffuse and slowly growing, and composed of well differentiated astrocytic cells subdivided into fibrillary, protoplasmic or gcmistocytic types. Although 'benign' they widely infiltrate surrounding brain and lack a definitive edge or capsule. A further low grade type - the pilocytic (or 'juvenile') astrocytoma occurs in the hypothalamic region as well as in the optic nerve (page 336) and cerebellum (page 319). Since partial resection may result in a cure, some believe pilocytic astrocytomas are 'hamartomas' - mesodermal cell rests, rather than true tumours.

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