Before you can understand how cancer grows, first you have to know that your body is made up of millions of cells. Because those cells can divide – one cell becomes two, two become four, four become eight and so on – every day there are a lot more of them. Fortunately, every day a lot of them die too, because otherwise you would have too many. There has to be some kind of balance.
With cancer, something goes wrong with those cells. One of the cells breaks up and gets ill. The poorly, malignant cells divide and divide and keep on growing. Such a malignant cell is called a cancer cell. They gather together, push the healthy cells away, can even grow right through everything and can wander around the body. Something has to be done to stop those cancer cells!