Cancer Health Center

What is leukemia?

Leukemia is cancer of the blood cells. It starts in the bone marrow, the soft tissue inside most bones. Bone marrow is where blood cells are made.

When you are healthy, your bone marrow makes:

• White blood cells, which help your body fight infection.
• Red blood cells, which carry oxygen to all parts of your body.
• Platelets, which help your blood clot.

When you have leukemia, the bone marrow starts to make a lot of abnormal white blood cells, called leukemia cells. They don't do the work of normal white blood cells, they grow faster than normal cells, and they don't stop growing when they should.

Over time, leukemia cells can crowd out the normal blood cells. This can lead to serious problems such as anemia, bleeding, and infections. Leukemia cells can also spread to the lymph nodes or other organs and cause swelling or pain.

Are there different types of leukemia?

There are several different types of leukemia. In general, leukemia is grouped by how fast it gets worse and what kind of white blood cell it affects.

• It may be acute or chronic. Acute leukemia gets worse very fast and may make you feel sick right away. Chronic leukemia gets worse slowly and may not cause symptoms for years.
• It may be lymphocytic or myelogenous. Lymphocytic (or lymphoblastic) leukemia affects white blood cells called lymphocytes. Myelogenous leukemia affects white blood cells called myelocytes.

The four main types of leukemia are:

• Acute lymphoblastic leukemia, or ALL.
• Acute myelogenous leukemia, or AML.
• Chronic lymphocytic leukemia, or CLL.
• Chronic myelogenous leukemia, or CML.

In adults, chronic lymphocytic leukemia (CLL) and acute myelogenous leukemia (AML) are the most common leukemias. In children, the most common leukemia is acute lymphoblastic leukemia (ALL). Childhood leukemias also include acute myelogenous leukemia (AML) and other myeloid leukemias, such as chronic myelogenous leukemia (CML) and juvenile myelomonocytic leukemia (JMML).

There are less common leukemias, such as hairy cell leukemia. There are also subtypes of leukemia, such as acute promyelocytic leukemia (a subtype of AML).

What causes leukemia?

Experts don't know what causes leukemia. But some things are known to increase the risk of some kinds of leukemia. These things are called risk factors. You are more likely to get leukemia if you:

• Were exposed to large amounts of radiation.
• Were exposed to certain chemicals at work, such as benzene.
• Had some types of chemotherapy to treat another cancer.
• Have Down syndrome or some other genetic problems.
• Smoke.

But most people who have these risk factors don't get leukemia. And most people who get leukemia do not have any known risk factors.

What are the symptoms?

Symptoms may depend on what type of leukemia you have, but common symptoms include:

• Fever and night sweats.
• Headaches.
• Bruising or bleeding easily.
• Bone or joint pain.
• A swollen or painful belly from an enlarged spleen.
• Swollen lymph nodes in the armpit, neck, or groin.
• Getting a lot of infections.
• Feeling very tired or weak.
• Losing weight and not feeling hungry.

How is leukemia diagnosed?