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Intrinsic brain tumours- Glioma, metastasis and pituitary tumours

Intrinsic tumours are those that grow within the substance of the brain itself rather than from the coverings surrounding it. There are a great many types arising form the various differnet cells within the nervous system. Below we describe some of the most commonly occurring.

Brain metastasis

Overall the commonest brain tumour encountered is metastasis. That is a malignant tumour which has spread from a location elsewhere in the body. For many cancers this is seen at a very late stage in the disease. Some tumours are more likely to spread to the nervous system and include:

  • Lung
  • Breast
  • Melanoma (skin)
  • Kidney
  • Testicular
  • Colorectal
  • Lymohoma
  • Leukaemia

If a solitary metastasis in the brain is amenable to removal this may afford the best chance of controlling the disease within the brain and facilitate the subsequent use of radiotherapy. Radiosurgery may be deployed as an alternative in appropriate cases.

 

Glioma

The most common primary brain tumours arise not from the nerve cells themselves but their supporting cells called glial cells. Such tumours are termed glioma. There are different subsets of glial cell and if the cell of origin is apparent on neuropathological examination the tumour may be named accordingly e.g. astrocytoma, oligodendroglioma. The most aggressive of these tumours exhibit very primitive, aggressively growing cells and the cell of origin may not be apprarent. They are classified according to their cellular and genetic characterisitics into grades by the World Health Organisation (WHO) ranging from grade I (a benign tumour) to grade IV, the most agressive.Glioblastoma Multiforme is a name given to grade IV tumours with primitive, malignant cell types mixed with areas of lifeless tissue (necrosis).

The most malignant of these tumours are very difficult to treat and although survival has significantly increased in recent years most will progress in time. Management is by a combination of surgical biopsy, agressive removal if feasible and chemoradiotherapy under the supervision of specialist oncologists.

Low grade glioma (Grade 1 and 2 astrocytoma, oligodendroglioma for example) pose some of the greatest uncertainties in neurosurgery. These tumours may behave very benignly for years or decades before transforming to a higher grade tumour that may prove impossible to control. Grade I tumours are often amenable to complete removal but are unfortunately uncommon in adults. Low grade tumours may not be possible to remove completely but may be controlled by medical meands for prolonged periods of time. In recent years a more aggressive approach to these lesions in adults has been advocated. It has proven difficult to prove that exposing patients to the risk of surgical and potentially toxic chemo-radiation, while the tumour is still of low grade, translates into long term health benefit.

Low grade glioma is the most common brain tumour in children in is managed quite differently to adults by specialist paediatric neuro-oncological teams.

Surgical removal can be effective in providing short to medium-term control of higher grade tumours. Having a tissue sample to examine is also vital in identifiying molecular subtypes of tumour some of which are peculiarly susceptible to medical therapy, conferring extra years of control in some cases.

 

Tumours of the Pituitary Gland and Neuroendocrine Disease

The pituitary gland is found at the base of the brain and is respnsible for releasing chemical controllers of the bodies function into te blood stream- hormones. The gland itself lies close by the visual apparatus and if large tumours develop within it, they may press upon the optic nerves causing loss of vision. Rarely there is bleeding within the gland or a tumour outgrowns its blood supply, suddenly swelling and causing headaches with loss of peripheral vision- pituitary apoplexy. Such sudden swelling can also be accompanied by catastrophic failure of the hormonal control of body chemistry and require urgent hormonal replacement as well as surgical treatment.

Benign tumours may develop in the pituitary gland whichoroduces an excess of hormone by themselves. These tumours may only manifest with the symptoms caused by an excess of that hormone e.g Prolactin, glucocorticoids (Cushing's Syndrome). Some of tumours may be effectively treated by medication alone without recourse to surgery. Occasionally radioterapy or radiosurgery are used to treat tuumours within the galnd particularly if they have proved difficult to control hiterto. Rarely malignancy can develop and metastasis to the pituitary gland may be encountered.

Benign but troublesome growth in cells left over from the embryos development may give rise to a tumour called Craniopharyngioma in both children and adults. These cystic tumours may also affect the visual pathways or disrupt hormonal balance causing symptoms such as depression, disrupted sleep, weight/appetite fluctuation and infertility. The assistance of an expert physician to advise on hormonal diagnosis and therapy - an Endocrinologist- is vital.