What is brain tumour?

A brain tumour, like a tumour anywhere else in the body, is a result of an abnormal proliferation of cells in the brain. A primary brain tumour is one where the tumour originates from the brain cells. Secondary brain tumours are cancers originating elsewhere in the body and spreading to the brain through the blood stream. It may be mentioned that some chronic infections like tuberculosis and fungal infections often produce a tumour like moss in the brain which may mimic a cancerous lesion. A brain tumour may directly destroy brain cells or it may cause brain dysfunction by various other means.

The skull is a hard bony structure and thus provides only limited space to the structures within. Since the brain does not have any space to expand, a space-occupying tumour may be especially dangerous. Brain tumours can cause indirect damage by compressing brain tissue, inflammation of the brain (cerebral oedema) and increasing the pressure within the brain (intracranial pressure) by interfering with the circulation of brain fluid (cerebrospinal fluid or CSF).

Though most tumours are classified as 'malignant' or 'benign', brain tumours are usually classified as "high grade" or rapidly growing and "low grade" or slow growing. This is because even non-cancerous brain tumours may be life threatening since they do not have space to grow and thus endanger other parts of the brain.