Cancer: Principles
- Cells in the body divide by mitosis to produce more cells - this is essential for growth and to replace cells that are lost or damaged
- Cells of the intestines are constantly dividing to replace those that are shed as food move through the digestive system
- Mitosis is just one part of the cell cycle which is regulated by many different genes to ensure that cells divide only when they need to and stop when required
- Cancer is caused as a result of changes in the DNA of cells that lead to uncontrolled growth and division - this can result in the formation of a tumour (a mass of cells)
- Usually tumours form as a result of loss of control of the cell cycle
- Not all tumours are considered cancerous
- Benign tumours are growths of abnormal cells which are contained in one area, usually within a membrane
- Crucially, benign tumours do not invade other parts of the body
- Malignant tumour cells are cancers – the cells invade neighbouring tissues and spread to different parts of the body via the blood and lymphatic system where they form secondary tumours
- Malignant tumours are more likely to disrupt the functioning of the organ they originate in (as they invade healthy tissue) and the organs they spread to – this is why they are dangerous and how they lead to death
