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:
- White blood cells that fight infection and disease.
- Platelets that form blood clots to stop bleeding.
- 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.
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.
Signs and symptoms of hairy cell leukemia include infections, tiredness, and pain below the ribs.These and other signs and symptoms may be caused by hairy cell leukemia or by other conditions. Check with your doctor if you have any of the following:
- 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.
Tests that examine the blood and bone marrow are used to detect (find) and diagnose hairy cell leukemia.The following tests and procedures may be used:
- Peripheral blood smear: A procedure in which a sample of blood is checked for cells that look "hairy," the number and kinds of white blood cells, the number of platelets, and changes in the shape of blood cells.
- Blood chemistry studies: A procedure in which a blood sample is checked to measure the amounts of certain substances released into the blood by organs and tissues in the body. An unusual (higher or lower than normal) amount of a substance can be a sign of disease in the organ or tissue that makes it.
- Bone marrow aspiration and biopsy: The removal of bone marrow, blood, and a small piece of bone by inserting a hollow needle into the hipbone or breastbone. A pathologist views the bone marrow, blood, and bone under a microscope to look for signs of cancer.
- Immunophenotyping: A laboratory test in which the antigens or markers on the surface of a blood or bone marrow cell are checked to see what type of cell it is. This test is done to diagnose the specific type of leukemia by comparing the cancer cells to normal cells of the immune system.
- Flow cytometry: A laboratory test that measures the number of cells in a sample, the percentage of live cells in a sample, and certain characteristics of cells, such as size, shape, and the presence of tumor markers on the cell surface. The cells are stained with a light-sensitive dye, placed in a fluid, and passed in a stream before a laser or other type of light. The measurements are based on how the light-sensitive dye reacts to the light.
- Cytogenetic analysis: A laboratory test in which cells in a sample of tissue are viewed under a microscope to look for certain changes in the chromosomes.
- CT scan (CAT scan): A procedure that makes a series of detailed pictures of areas inside the body, taken from different angles. The pictures are made by a computer linked to an x-ray machine. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly. This procedure is also called computed tomography, computerized tomography, or computerized axial tomography. A CT scan of the abdomen may be done to check for swollen lymph nodes or a swollen spleen.
Certain factors affect treatment options and prognosis (chance of recovery).The treatment options may depend on the following:
- The number of hairy (leukemia) cells and healthy blood cells in the blood and bone marrow.
- Whether the spleen is swollen.
- Whether there are signs or symptoms of leukemia, such as infection.
- Whether the leukemia has recurred (come back) after previous treatment.
- Whether the hairy cell leukemia does not grow or grows so slowly it does not need treatment.
- Whether the hairy cell leukemia responds to treatment.