TABLE OF CONTENTS Tumours are, literally, swellings. They have, however, come to mean a special kind of swelling that, popularly, is called a growth or, if it is a particularly dangerous growth, it is called a cancer . These tentative definitions are made with deference to a highly respected German pathologist, Rudolf Virchow (1821-1902), who once remarked that no man, even under torture, could say exactly what a rumour is. Nevertheless, a workable definition is that a tumour is a tissue mass formed as a result of abnormal, excessive and inappropriate cell proliferation, the growth of which continues indefinitely and regardless of the mechanisms that control normal cellular proliferation.
Nineteenth century pathologists divided tumours into benign, simple or innocent rumours and malignant rumours. Benign rumours (which can still be dangerous in some situations) remain localised, forming a single mass that frequently produces no symptoms and can usually be excised completely. If symptoms are experienced, these are usually due to pressure on adjacent tissues or to excessive hormone production. Malignant tumours invade adjacent tissues and their cells may dissociate and spread through blood and lymphatic vessels to other parts of the body, where they may lodge, divide and give rise to secondary rumours or metastases. These are difficult to control, and account for most of the approximately 25% of the deaths due to cancer in most developed countries.
Cancer as a cause of death is not negligible at any age, but it is primarily a terminal illness in aged populations. Carcinogenesis...
