What is Leukemia? (loo-KEE-mee-a)

 Leukemia is cancer of the blood:

• It is a cancer that starts in blood-forming tissue such as the bone marrow, and causes large numbers of blood cells to be produced and enter the bloodstream.
• New cells form when the body does not need them, and old cells do not die when they should.

Blood cells form in the bone marrow. Bone marrow is the soft material in the center of most bones. Immature blood cells are called stem cells and blasts. Most blood cells mature in the bone marrow and then move into the blood vessels. Blood flowing through the blood vessels and heart is called the peripheral blood.

In people with leukemia, the bone marrow produces abnormal white blood cells. The abnormal cells are leukemia cells. At first, leukemia cells function almost normally. In time, they may crowd out normal white blood cells, red blood cells, and platelets. This makes it hard for blood to do its work.

Diagnosis

In asking 'what is leukemia?', if someone has symptoms that look like leukemia, a doctor may do a physical exam as well as ask about the patient's personal and family medical history. The doctor also may order laboratory tests, especially blood tests.

The exams and tests may include the following:

• Physical exam: the doctor checks for swelling of the lymph nodes, spleen, and liver.
  
• Blood tests: these reveal the level of blood cells. Leukemia causes a very high level of white blood cells. Conversely, it causes low levels of platelets and hemoglobin. These are found inside red blood cells. The lab also may check the blood for signs that leukemia has affected other organs such as the liver and kidneys.
  
• Biopsy: the doctor takes a sample of bone marrow from the hipbone or another large bone. A pathologist will examine the sample under a microscope. The removal of tissue to look for cancer cells is called a biopsy. A biopsy is the only absolutely sure way to know whether leukemia cells are within the bone marrow.

There are two methods the doctor can use to obtain bone marrow. 

Some patients will have both procedures:

1. Bone marrow aspiration: The doctor uses a needle to remove samples of bone marrow.

2. Bone marrow biopsy: The doctor uses a very thick needle to remove a small piece of bone and bone marrow.

• Local anesthesia helps to make the patient more comfortable.
• Cytogenetics: the lab observes the chromosomes of cells from samples of peripheral blood, bone marrow, or lymph nodes.
• Spinal tap: the doctor takes some of the cerebrospinal fluid (the fluid that fills the spaces in and around the brain and spinal cord). The doctor uses a long, thin needle to remove fluid from the spinal column. The procedure takes about 30 minutes and is performed with local anesthesia. The patient must lie flat for several hours afterward to keep from getting a headache. The lab checks the fluid for leukemia cells or other signs of problems.
• Chest x-ray: the x-ray can reveal signs of disease in the chest.

Public Domain Information courtesy of:  National Cancer Institute