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Leukemia, or cancer of the blood, was first recognized as a distinct disease around 1830 in Germany. The term "leukemia" comes from the Greek words meaning "white blood" and refers to the whitish or pale pink blood that was first noticed in patients with extremely high numbers of circulating malignant white cells. Leukemia is more accurately described as a cancerous disorder not of the blood itself, but rather of the organs that manufacture the blood cells. These organs, principally the bone marrow and the lymph system (the lymph nodes and spleen), are the places in which normal red cells, white cells, lymph cells, and platelets originate and grow to maturity before entering the bloodstream. The cancerous counterparts of these normal cells go through approximately the same process but with important differences in rate, number, and ability to function.
Although leukemia is the most common of the childhood cancers, it is actually far more common in adults. Approximately 25,000 new cases of leukemia are diagnosed annually in the United States, 22,500 of them in adults and 2,500 in children. Men are affected by leukemia 30 percent more frequently than women. About 17,000 people die from the disease each year. About half of the newly diagnosed cases of leukemia fall into the acute category; the rest are chronic.
Most of the advanced industrial nations have experienced an apparent increase in the incidence of leukemia since the 1930s. Epidemiologists and biostatisticians have not determined whether this is a true increase or whether it can be attributed to improved diagnostic methods and wider access to health care. One important contributing factor is the rising proportion of elderly people in these countries, since cancers of all kinds are more likely to develop in older populations. |
