Leukemia is a cancer of the blood cells. Types of leukemia are named after the specific blood cell that becomes cancerous, such as the lymphocytic cells (white blood cells) or the myeloid cells (cells of the bone marrow, the spongy, red tissue in the inner part of large bones). There are four main types of leukemia in adults:
There are other, less common types of leukemia, but they are generally subcategories of one of the four main categories. This section focuses on prolymphocytic leukemia (PLL) and hairy cell leukemia (HCL), which are chronic B-cell leukemias. B cells are a specific type of lymphocyte that normally help to produce antibodies for the immune system.
In PLL, large numbers of immature lymphocytes, or prolymphocytes, are present in the blood. This type of leukemia may occur together with CLL, or CLL may transform into PLL.
HCL is a slow-growing form of leukemia. It is called “hairy cell” because the abnormal lymphocytes have projections that look like hair when seen under a microscope. As these cells multiply, they accumulate in the bone marrow, blood, and spleen. Because these lymphocytes are abnormal, they do not perform the normal work of lymphocytes in fighting disease and infection, and eventually may crowd out the normal cells. HCL typically responds well to treatment.
Statistics
In 2009, an estimated 44,790 people of all ages (25,630 men and 19,160 women) in the United States will be diagnosed with leukemia. HCL accounts for 2% of all leukemia cases. An estimated 15,490 people (9,200 men and 6,290 women) in the United States will be diagnosed with CLL. There are no current estimates for PLL.
Cancer statistics should be interpreted with caution. These estimates are based on data from thousands of cases of this type of cancer in the United States, but the actual risk for a particular individual may differ. It is not possible to tell a person how long he or she will live with leukemia.
Statistics adapted from the American Cancer Society's publication, Cancer Facts and Figures 2009.
Find out more about basic cancer terms used in this section.
Last Updated: January 08, 2009
