What Is Leukemia?
There are multiple forms of leukemia, the most common of which affects mainly adults. Each form of leukemia is defined by the type of blood cell that becomes cancerous. So to understand leukemia, we have to look at the different types of blood cells as well as where and how they are formed.4
Blood cells are produced in the marrow of the bones of the chest, pelvis, and upper parts of the arms and legs. They all start from a single type of cell, the "pluripotent stem cell." This "grandfather" of all blood cells is constantly dividing to produce 2 other stem cells:
- Lymphoid stem cells, which produce lymphocytes. There are 2 kinds of lymphocytes:
- Myeloid stem cells, which produce red blood cells and other types of white blood cells
The words lymphoid and myeloid are important because they are used to describe the 2 main kinds of leukemia. These stem cells go through a series of changes to become a blood cell. This process is called differentiation. A stem cell can become cancerous at any time during this development. If it happens at an early stage, the cancer cells will not function normally. These are called undifferentiated cells. The stage of differentiation of the cancer cells will affect how the disease develops and how it should be treated.
Acute or chronic
Leukemias can also be described according to characteristics of onset and how fast they progress1:
- Acute—means they usually come on abruptly and progress rapidly; once diagnosed will soon be fatal unless treated
- Chronic—means they usually progress slowly and may not cause any symptoms until many years later
Thus, we have 4 different types of leukemia, which all behave differently4:
- Acute myeloid leukemia (AML)
- Chronic myeloid leukemia (CML)
- Acute lymphocytic leukemia (ALL)
- Chronic lymphocytic leukemia (CLL)
The type of leukemia will determine the symptoms experienced, the treatment received, and the chances of being cured.