Uncontrolled Cell Division
- Cells in the body divide by mitosis to produce more cells – this is essential for growth and to repair damaged cells
- For example, the cells of the intestines are constantly dividing to replace those that are shed as food moves 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 mutations in the DNA of cells that lead to uncontrolled cell 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
Types of Tumour
- There are two main types of tumour:
- Benign tumours
- Malignant tumours
- 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
- This means these tumours are not considered cancerous
- Malignant tumours are cancerous – the cells of these tumours 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
