This literally means any swelling, but the term is not usually aimed at temporary swellings caused by acute inflammation. The consequences locally, however, of chronic inflammation – like TUBERCULOSIS, SYPHILIS and LEPROSY, are sometimes classed as tumours, according to their size and appearance. Most people would understand the term to imply some form of cancer.
Some are of an infective nature, as already stated; some arise as the result of injury, and several contributing factors are mentioned under the heading of CANCER. Traditionally tumours have been divided into benign (simple) and malignant. They are now classed according to the tissues of which they are built, somewhat as follows:
simple tumours of normal tissue.
hollow tumours or cysts, generally of simple nature.
malignant tumours: (a) of cellular structure, resembling the cells of skin, mucous membrane, or secreting glands; (b) of connective tissue.
Benign tumours can be harmful if their size or position distorts or damages nerves, blood vessels or organs. Usually, they are easily removed by surgery and do not recur. Malignant tumours or cancers are harmful and potentially lethal, not just because they erode tissues locally but because many of them spread, either by direct growth or by ‘seeding’ to other parts – ‘metastasising’. Malignant tumours arise because of an uncontrolled growth of previously normal cells. Heredity, environmental factors and lifestyle all play a part in malignancy (ONCOGENES). Symptoms are caused by local spread and as a result of metastases. These cause serious local damage, for example, in the brain or lungs, as well as disturbing the body's metabolism. Unless treated with CHEMOTHERAPY, RADIOTHERAPY or surgery or a combination of these, malignant tumours are ultimately fatal. Many, however, can now be cured.
The type of cell and organ site determine the characteristics of a malignant tumour. The prognosis (outlook) for a patient with a malignant tumour depends largely upon its precise type and to some extent on how early it is diagnosed. Staging criteria have been developed to assess the local and metastatic spread of a tumour, its size and likely sensitivity to the types of available treatment. The ability to locate a tumour and its metastases accurately has vastly improved with the introduction of radionuclide and ULTRASOUND scanning, CT scanning and magnetic resonance imaging (MRI). Screening for cancers such as those in the breast, cervix, colorectal region and prostate help early diagnosis and usually improve treatment outcomes.