The Facts
Leukemia is a type of cancer of the bone marrow and blood. It was first discovered in the 19th century by European physicians, who called it Weisses blut or white blood. Eventually, the disease was called leukemia, derived from the Greek words leukos meaning white and haima meaning blood.
Chronic lymphocytic leukemia is one of several different types of leukemia. It's also referred to as chronic lymphoid leukemia, or CLL. It is characterized by a gradual increase in the number of white blood cells, or lymphocytes, in the blood and the bone marrow. White blood cells are important because they fight bacteria and protect the body from possible infections.
In chronic lymphocytic leukemia, cancerous lymphocytes build up in the lymph nodes, liver, and spleen, causing these areas to get larger. There are a number of kinds of chronic lymphocytic leukemia, and they are classified by the type of lymphocyte involved, such as B-cell or T-cell. B-cell leukemia is the most common type. T-cell leukemia is much less common. Other types include Sézary syndrome, and hairy cell leukemia, a rare type of leukemia that produces abnormal white blood cells that, when viewed through a microscope, have hair-like projections.
The incidence of chronic lymphocytic leukemia increases with age - 90% of cases occur in people older than 50. By 70 years of age, 15 out of 100,000 people may have it. Men are two to three times more likely than women to develop the disease. Researchers believe that genetics plays a role in its development because it is rare in Japan and China, and remains uncommon in Japanese people who have moved to North America.