Students should be able to describe cancer as the result of changes in cells that lead to uncontrolled growth and division. • Benign tumours are growths of abnormal cells which are contained in one area, usually within a membrane. They do not invade other parts of the body. • Malignant tumour cells are cancers. They invade neighbouring tissues and spread to different parts of the body in the blood where they form secondary tumours. • Scientists have identified lifestyle risk factors for various types of cancer. There are also genetic risk factors for some cancers.