Chronic lymphocytic leukemia (CLL) is a cancer of the blood and bone marrow. Lymphocytes are a type of white blood cell. With CLL, the bone marrow makes too many of these cells. CLL begins in mature lymphocytes. It may be slow growing for many years with little or no trouble. It may also progress to acute lymphoblastic leukemia (ALL), a more aggressive form of leukemia. Some forms of CLL may be more serious.

White Blood Cells
White Blood Cells
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CLL can also be associated with the presence of chronic lymphocytic lymphoma. This is a small cell non-Hodgkin’s lymphoma. The abnormal cells in both cases may come from the same parent cell source. As a result, one of the signs of CLL may be swelling in the lymph nodes.

Cancer occurs when cells in the body become abnormal. They divide without control or order. Leukemia is cancer of the white blood cells and their parent cells. Leukemia cells do not function normally. In this case, they cannot fight infections. This means that the person is more likely to become infected with viruses or bacteria. The cancerous cells also overgrow the bone marrow. This forces other normal components, like platelets, out. Platelets are needed to help the blood clot. As a result, people with leukemia may bleed more easily.

The exact cause of CLL is unknown. Changes in chromosomes that occur during life have been associated with CLL. It is also associated with exposure to radiation and to toxic chemicals such as:

  • Benzene—common in agriculture, paint manufacture, and dye manufacture
  • Agent Orange—an herbicide used in the Vietnam war