How does cancer arise?

Our bodies are made of millions of cells, many of which wear out and die and need to be replaced. Sometimes, the process that creates replacement cells gets out of control, so that too many cells are produced, creating a lump or ‘tumour’. If the cells remain in the tumour, they are not ‘cancerous’, and the tumour is called ‘benign’. However, if the cells can leave the tumour and spread into other tissues, the cells are described as ‘cancerous’ and the tumour is called ‘malignant’.

A small sample of cells, called a biopsy, may be taken from a tumour and examined under a microscope to find out whether the tumour is benign or malignant.