Hairy cell leukemia is a type of cancer in which the bone marrow makes too many lymphocytes (a type of white blood cell).
Hairy cell leukemia is a cancer of the blood and bone marrow. This rare type of leukemia gets worse slowly or does not get worse at all. The disease is called hairy cell leukemia because the leukemia cells look "hairy" when viewed under a microscope.
Normally, the bone marrow makes blood stem cells (immature cells) that become mature blood cells over time. A blood stem cell may become a myeloid stem cell or a lymphoid stem cell.
A myeloid stem cell becomes one of three types of mature blood cells:
- Red blood cells that carry oxygen and other substances to all tissues of the body.
- White blood cells that fight infection and disease.
- Platelets that form blood clots to stop bleeding.
A lymphoid stem cell becomes a lymphoblast cell and then into one of three types of lymphocytes (white blood cells):
- B lymphocytes that make antibodies to help fight infection.
- T lymphocytes that help B lymphocytes make antibodies to help fight infection.
- Natural killer cells that attack cancer cells and viruses.
Blood cell development. A blood stem cell goes through several steps to become a red blood cell, platelet, or white blood cell.
In hairy cell leukemia, too many blood stem cells become lymphocytes. These lymphocytes are abnormal and do not become healthy white blood cells. They are also called leukemia cells. The leukemia cells can build up in the blood and bone marrow so there is less room for healthy white blood cells, red blood cells, and platelets. This may cause infection, anemia, and easy bleeding. Some of the leukemia cells may collect in the spleen and cause it to swell.
This summary is about hairy cell leukemia. See the following PDQ summaries for information about other types of leukemia:
- Adult Acute Lymphoblastic Leukemia Treatment.
- Childhood Acute Lymphoblastic Leukemia Treatment.
- Chronic Lymphocytic Leukemia Treatment.
- Adult Acute Myeloid Leukemia Treatment.
- Childhood Acute Myeloid Leukemia/Other Myeloid Malignancies Treatment.
- Chronic Myelogenous Leukemia Treatment.
Gender and age may affect the risk of hairy cell leukemia.
Anything that increases your chance of getting a disease is called a risk factor. Having a risk factor does not mean that you will get cancer; not having risk factors doesn't mean that you will not get cancer. Talk with your doctor if you think you may be at risk. The cause of hairy cell leukemia is unknown. It occurs more often in older men.
Possible signs of hairy cell leukemia include tiredness, infections, and pain below the ribs.
These and other symptoms may be caused by hairy cell leukemia. Other conditions may cause the same symptoms. Check with your doctor if you have any of the following problems:
- Weakness or feeling tired.
- Fever or frequent infections.
- Easy bruising or bleeding.
- Shortness of breath.
- Weight loss for no known reason.
- Pain or a feeling of fullness below the ribs.
- Painless lumps in the neck, underarm, stomach, or groin.