ABSTRACT
Cancer is not a single disease, as there are estimated to be over 200 different types of cancer, and it is a disease that can develop in any cells within the body. It is caused by changes occurring in normal cells which result in uncontrolled growth. Cancer cells lose those attributes that usually result in orderly growth and function. Normal cells are able to respond to external signals regulating growth but cancer cells do not respond to such signals and continue to grow in an unregulated manner. Although normal cells recognise when their life cycle is at an end and die (a process called apoptosis) cancer cells do not recognise these signals and are able to evade cell death. Cells are also normally able to recognise the limits of their growth in relation to other structures. For example, a liver cell will stop replicating when the structure has sufficient cells, while the cancer cell will continue growing, thereby invading surrounding healthy tissues. All cells require a sufficient blood supply in order to thrive and cancer cells have the ability to develop their own blood supply by producing signals that stimulate the production of a new blood supply (called angiogenesis). Cancer cells are also able to travel to other parts of the body via the blood system and the lymphatic system (that is, to metastasise) where they can then infiltrate other organs (Souhami and Tobias 2005).
