What You Need to Know
Leukemia is the name given to several types of cancer that begin in the tissue that forms blood. To understand leukemia, it helps to know how normal blood cells form.
Normal Blood Cells
Most blood cells develop in the marrow, the soft material at the center of most bones. Bone marrow contains hematopoietic stem cells, which can transform into different kinds of blood cells, depending on what kind your body needs at a particular time. When cells grow old or are damaged, they die, and hematopoietic stem cells replace them.
Each type of blood cell has a special job:
- White blood cells help fight infection. There are several types of white blood cells.
- Red blood cells carry oxygen to tissues throughout the body.
- Platelets help form blood clots to control bleeding.
When someone develops leukemia, the bone marrow begins to make abnormal white blood cells, which are leukemia cells. Unlike normal blood cells, leukemia cells don't die when they should. They may crowd out normal white blood cells, red blood cells, and platelets. This makes it hard for normal blood cells to do their work.
Types of Leukemia
The various types of leukemia are organized into two groups, based on how quickly the disease develops and gets worse, and the type of cells in which the cancer develops. Leukemia is either chronic (which usually gets worse slowly) or acute (which usually gets worse quickly).
The two types of leukemia can be further organized into groups that are based on the type of white blood cell that is affected — lymphoid or myeloid. Leukemia that affects lymphoid cells is called lymphoid, lymphocytic, or lymphoblastic leukemia. Leukemia that affects myeloid cells is called myeloid, myelogenous, or myeloblastic leukemia:
Early in the disease, the leukemia cells can still do some of the work of normal white blood cells. People may not have any symptoms at first. Doctors often discover chronic leukemia during a routine checkup, before there are any symptoms. Slowly, chronic leukemia gets worse. As the number of leukemia cells in the blood increases, people experience symptoms, such as swollen lymph nodes or infections. When symptoms do appear, they are usually mild at first but gradually get worse.
- Chronic lymphocytic leukemia (CLL): CLL affects lymphoid cells and usually grows slowly. It accounts for more than 16,000 new cases of leukemia each year. Most people diagnosed with the disease are over age 55. It almost never affects children. CLL is treated by the Lymphoma/Myeloma Team.
- Chronic myeloid leukemia (CML): CML affects myeloid cells and usually grows slowly at first. It accounts for nearly 5,400 new cases of leukemia each year. It affects mainly adults.
The leukemia cells can't do any of the work of normal white blood cells. The number of leukemia cells increases rapidly. Acute leukemia usually worsens quickly.
- Acute myeloid leukemia (AML): AML affects myeloid cells and grows quickly. It accounts for more than 13,780 new cases of leukemia each year. It occurs mostly in adults.
- Acute lymphocytic (lymphoblastic) leukemia (ALL): ALL affects lymphoid cells and grows quickly. It accounts for more than 6,050 new cases of leukemia each year. ALL is the most common type of leukemia in young children, but it also affects adults.
A few other, rarer types of leukemias, including hairy cell leukemia, account for more than 6,000 new leukemia diagnoses each year.
Signs & Symptoms
The symptoms of leukemia depend on the number of leukemia cells and where the cells collect in the body. They include:
- Swollen lymph nodes that usually don't hurt (especially lymph nodes in the neck or armpit)
- Fevers or night sweats
- Frequent infections or poor healing of minor cuts
- Feeling weak or tired
- Bleeding and bruising easily (bleeding gums, purplish patches in the skin, or tiny red spots under the skin)
- Swelling or discomfort in the abdomen (from a swollen spleen or liver)
- Weight loss for no known reason
- Pain in the bones or joints