Home > Encyclopedia of Cancer > Chronic Lymphocytic Leukemia

Definition

Chronic lymphocytic leukemia (CLL) is a cancer of white blood cells. In CLL, mature white blood cells of certain types called lymphocytes function abnormally and cause disease.

Description

Chronic leukemia is a cancer that starts in the blood cells made in the bone marrow. The bone marrow is the spongy tissue found in the large bones of the body. The bone marrow makes precursor cells called "blasts" or "stem cells" that mature into different types of blood cells. Unlike acute leukemias, in which the process of maturation of the blast cells is interrupted, in chronic leukemias, most of the cells do mature and only a few remain as immature cells. However, even though the cells appear normal, they do not function as normal cells.

The different types of cells...