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 not at all. The disease is called hairy cell leukemia because the leukemia cells look "hairy" when viewed under a microscope.

Normally, the bone marrow produces stem cells (immature cells) that develop into mature blood cells. There are 3 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.

In hairy cell leukemia, too many stem cells develop into a type of white blood cell called lymphocytes. These lymphocytes may also be called leukemic cells. There are 3 types of lymphocytes.

• 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, the B lymphocytes do not work normally. Also, as the number of lymphocytes increases in the blood and bone marrow, 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.

Gender and age may affect the risk of developing hairy cell leukemia.

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.

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 biopsy: The removal of a small piece of bone and bone marrow by inserting a needle into the hipbone or breastbone. A pathologist views both the bone and bone marrow samples under a microscope to look for signs of cancer.

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.

Stages of Hairy Cell Leukemia

Staging is the process used to find out how far the cancer has spread. There is no standard staging system for hairy cell leukemia. The disease is grouped as untreated, progressive, or refractory.

Untreated hairy cell leukemia

The hairy cell leukemia is newly diagnosed and has not been treated except to relieve symptoms such as weight loss and infections. In untreated hairy cell leukemia, some or all of the following conditions occur:

• Hairy (leukemia) cells are found in the blood and bone marrow.
• The number of red blood cells, white blood cells, or platelets may be lower than normal.
• The spleen may be larger than normal.

Progressive hairy cell leukemia

In progressive hairy cell leukemia, the leukemia has been treated with either chemotherapy or splenectomy (removal of the spleen) and one or both of the following conditions occur:

• There is an increase in the number of hairy cells in the blood or bone marrow.
• The number of red blood cells, white blood cells, or platelets in the blood is lower than normal.

Relapsed or Refractory Hairy Cell Leukemia

Relapsed hairy cell leukemia has come back after treatment. Refractory hairy cell leukemia has not responded to treatment.

Tags: Leukemia

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