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CANCER - What is Cancer?

Normally, this turnover of cells takes place in a controlled way. If, for some reason, the process goes out of control, the cells are produced more rapidly, developing into a lump which is called a tumour. Tumours can be benign or malignant.

In a benign tumour the cells do not spread to other parts of the body and so are not cancerous. If they continue to grow at the original site, however, they may cause a problem by pressing on the surrounding organs.

A malignant tumour consists of cancer cells which have the ability to spread beyond the original site. If the tumour is left untreated, it may invade and destroy surrounding tissue. Sometimes cells break away from the original (primary) cancer and spread to other organs in the body through the bloodstream or lymphatic system. When these cells reach a new site they may go on dividing and form a new tumour, often referred to as a secondary or a metastasis.

Doctors can tell whether a tumour is benign or malignant by examining a small sample of cells under a microscope. This is called a biopsy.

Brain tumours
Primary brain tumours rarely spread outside the brain. In benign brain tumours, if the tumour can be removed successfully it should not cause any further problems. However, it may sometimes be difficult to remove a benign brain tumour because of where it is situated and the damage that would be caused by surgery. A small proportion do regrow slowly and these recurrences can usually be removed, when necessary, by a further operation, or treated with radiotherapy.

Primary malignant brain tumours are most likely to cause problems by invading the normal brain tissue which surrounds them.

Many malignant brain tumours are secondaries to cancer elsewhere in the body - most commonly, from the lung or the breast. Your doctor will be able to tell you if yours is a primary or secondary tumour.