Cancer occurs when, for unknown reasons, cells divide without control or order.
All parts of the body ar e made up of cells that normally divide to produce more cells only when the body needs them. When cancer occurs, cells keep dividing even when new cells are not needed. The change from normal to cancerous cells requires several separate, different gene alterations. Malignant tumors can invade, damage, and destroy nearby tissues and spread to other parts of the body. A benign tumor won't spread to other parts of the body, but local tissue may be damaged and the growth may need to be removed.