Growths in the body caused by the abnormal proliferation of cells. Some food components are thought to possess antitumour activity. Tumours may be benign (i.e. grow at one site only) or malignant (i.e. they destroy the tissue in which they arise and spread to other parts of the body). Benign tumours, which are covered by a capsule, are usually harmless but may become very large, exerting pressure on neighbouring tissues and producing severe effects. In malignant tumours, which are not enclosed by a capsule, cell division is rapid; cells show partial or complete loss of function and bear little resemblance to the tissue cells from which they originated. Malignant tumours cause extensive damage.