• General Information About Hairy Cell Leukemia
• Stages of Hairy Cell Leukemia
• Relapsed or Refractory Hairy Cell Leukemia
• Treatment Option Overview
• Treatment Options for Hairy Cell Leukemia
• To Learn More About Hairy Cell Leukemia
• Get More Information From NCI
• Changes to This Summary (07/15/2011)
• About PDQ

General Information About Hairy Cell Leukemia

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 develop into mature blood cells over time. A blood stem cell may become a myeloid stem cell or a lymphoid stem cell.

The myeloid stem cell develops into one of three types of mature blood cells:

• Red blood cells that carry oxygen and other materials to all tissues of the body.
• White blood cells that fight infection and disease.
• Platelets that help prevent bleeding by causing blood clots to form.

The lymphoid stem cell develops into 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 develop into lymphocytes. These lymphocytes are abnormal and do not become healthy white blood cells. They may also be called leukemic cells. The leukemic 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 developing 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. People who think they may be at risk should discuss this with their doctor. 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. A doctor should be consulted if any of the following problems occur:

• 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:

• Physical exam and history: An exam of the body to check general signs of health, including checking for signs of disease, such as a swollen spleen, lumps, or anything else that seems unusual. A history of the patient's health habits and past illnesses and treatments will also be taken.
• Complete blood count (CBC): A procedure in which a sample of blood is drawn and checked for the following:
  • The number of red blood cells, white blood cells, and platelets.
  • The amount of hemoglobin (the protein that carries oxygen) in the red blood cells.
  • The portion of the sample made up of red blood cells.
  
  
  Complete blood count (CBC). Blood is collected by inserting a needle into a vein and allowing the blood to flow into a tube. The blood sample is sent to the laboratory and the red blood cells, white blood cells, and platelets are counted. The CBC is used to test for, diagnose, and monitor many different conditions.
• 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.
• 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.
  
  Bone marrow aspiration and biopsy. After a small area of skin is numbed, a Jamshidi needle (a long, hollow needle) is inserted into the patient's hip bone. Samples of blood, bone, and bone marrow are removed for examination under a microscope.
• Immunophenotyping: A test in which the cells in a sample of blood or bone marrow are looked at under a microscope to check the pattern of proteins that are on the surface of the cells. Hairy cells have a certain pattern.
• 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 symptoms of leukemia, such as infection.
• Whether the leukemia has recurred (come back) after previous treatment.

The prognosis (chance of recovery) depends on the following:

• 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.

Treatment often results in a long-lasting remission (a period during which some or all of the signs and symptoms of the leukemia are gone). If the leukemia returns after it has been in remission, retreatment often causes another remission.