Inside the hollow area of the bones is a spongy core called bone marrow. It is here, that stem cells are produced. Stem cells are immature cells that can develop into components of blood: red blood cells, which carry oxygen to the body, white blood cells, or lymphocytes, which fight infection, and platelets, which help blood to clot. Chronic Myeloid Leukemia (CML) is a cancer of the white blood cells in the blood and bone marrow. CML develops from an acquired genetic abnormality. During cell division, some of the DNA from chromosome #9 is transferred to chromosome #22. This change is called the “Philadelphia chromosome.” When this abnormality occurs, the body signals too many stem cells to develop into a type of white blood cell called a granulocyte. Some of these granulocytes never mature. The immature granulocytes are called blasts. As the cancerous granulocytes and blasts multiply in the blood and bone marrow, fewer healthy white blood cells, red blood cells, and platelets are produced. Since the spleen also produces white blood cells, the cancerous cells can also develop in the spleen. Chronic Myeloid Leukemia develops slowly. Common symptoms are anemia, weight loss, fever, and an enlarged spleen. The current forms of treatment for patients with CML include: chemotherapy, radiation, stem cell transplantation, and surgery to remove the spleen. Prognosis depends on factors such as stage of disease and the age and overall health of the patient. Your doctor is the best source of information regarding treatment for your condition. It is important to discuss with your doctor which therapy, if any, is most appropriate for you.