Chronic lymphocytic leukemia (CLL) is a type of cancer that originates in the blood and bone marrow. It primarily leads to excessive production of a type of white blood cells. It is a chronic condition in that it progresses slowly in comparison with acute leukemia, though it can be rapid in progression in some individuals. In this type of cancer, there is excessive production of lymphocytes which are a form of white blood cells seen in the lymph nodes, spleen, bone marrow, liver and blood. These cells appear mature but are in fact immature and their large numbers potentially threaten the immune response to fight against diseases. The cells are known as monoclonal B lymphocytes and rarely may be of the T cell variety.
This type of cancer affects men more often than women at the ratio of 2:1. It is commonly found to occur among people of North American or European origin as opposed to eastern countries. In people over 55 years, the number of cases of CLL increases in comparison with those of lesser age groups. It represents about one quarter of all types of leukemias occurring the world over. CLL is seen to be present in higher numbers among asbestos workers, farmers, those employed in the rubber industry, etc.