Leukemia is a type of cancer. Cancer is a group of more than 100 diseases that have two important things in common. One is that certain cells in the body become abnormal. Another is that the body keeps producing large numbers of these abnormal cells.
Leukemia is cancer of the blood cells. Each year, nearly 27,000 adults and more than 2,000 children in the United States learn that they have leukemia.
To understand leukemia, it is helpful to know about normal blood cells and what happens to them when leukemia develops.