All cancers begin in cells. The body is made up of many types of cells. These cells grow and divide in a controlled way to produce more cells, as they are needed to keep the body healthy. When cells become old or damaged, they die and are replaced with new cells.
Normally cells grow and multiply in an orderly way, but sometimes something goes wrong with this process and cells will grow in an uncontrolled way.
The genetic material (DNA) of a cell can become damaged or changed, producing mutations that affect normal cell growth and division. When this happens, cells do not die when they should and new cells form when the body does not need them. The extra cells may result in abnormal blood cells or form a lump called a tumour.
The Beginnings of Cancer