CNS neoplasia I: Intracranial tumours

Published on 10/04/2015 by admin

Filed under Neurology

Last modified 10/04/2015

Print this page

This article have been viewed 1081 times

CNS neoplasia I

Intracranial tumours

In adults, primary intracranial tumours represent only 3% of tumour-related deaths, and have an annual incidence of 4–7 per 100 000. Intracranial metastases are more common. Intracranial tumours are the second most common tumour in childhood with an annual incidence of 2–3 per 100 000.

Pathology

Intracranial tumours can be divided into intrinsic and extrinsic (Table 1).

Table 1 Approximate frequency of different intracranial tumours

Tumour	Percentage of total	Comments
Intrinsic
Glioblastoma multiforme	20	High-grade glioma; poor prognosis
Astrocytoma	10 (48 in children)	Lower-grade glioma
Metastases	10*	Often multiple
Oligodendroglioma	5	Slow growing. Often frontal or temporal and calcifies
Ependymoma^†	5 (10 in children)	Arise from ependymal lining, usually of 4th ventricle
Medulloblastoma^†	5 (45 in children)	Arise from cerebellum. May metastasize within CNS
Primary CNS lymphoma	Rare except in AIDS	May be multifocal
Extrinsic
Meningioma^†	15	Arise from meninges and indent brain, may erode bone
Pituitary adenoma^†	7	Chiasmatic visual disturbance and endocrine effects
Schwannoma, e.g. of acoustic nerve^†	7	Benign
Other	16	Includes teratomas, pinealomas, etc.

Estimates are taken from a combination of series

† Potentially curable

* Metastases are much more common. This estimate is of those with solitary intracranial metastases

Intrinsic

Intrinsic tumours are within the substance of the brain, either primary or secondary. Primary intracranial tumours do not metastasize outside the CNS, and thus lack a central feature of malignant tumours elsewhere in the body. The concept of malignancy in primary intrinsic CNS tumours is therefore different from tumours elsewhere in the body. Malignancy in cerebral tumours is only a relative term and they are graded according to histopathological appearance (high = more malignant). They can arise from different cell lineages of neuroectodermal origin; gliomas arise from glial cells, and can be divided into specific cell types such as astrocytes (leading to astrocytomas and glioblastoma multiforme), oligodendrocytes (leading to oligodendrogliomas) and ependymal cells (leading to ependymomas). The histological type and grade are the primary determinants of prognosis. Different parts of a tumour may have different grades and a low-grade tumour may suddenly become more aggressive, in association with a change in histological characteristics.

The pattern of tumours differs in adults and children. In adults (see Table 1), 70% of tumours are supratentorial; in children, 70% of tumours are infratentorial.

Secondary intracranial tumours (or intracerebral metastases) occur in up to 20% of patients with cancer at postmortem examination. In most of these patients the primary tumour is known. The difficulty arises when intracranial metastases is the presentation. These most commonly arise from carcinoma of the lung and breast, and melanoma.

Extrinsic

Buy Membership for Neurology Category to continue reading. Learn more here

Related

Neurology An Illustrated Colour Text