Leukemia is a blood cell cancer that starts when the blood-producing bone marrow produces abnormal white blood cells. These abnormal cells displace the normally-functioning white blood cells (which fight infection), red blood cells (which carry oxygen from the lungs to all parts of the body) and platelets (which help control bleeding by forming blood clots). As the normal cells are displaced by the malignant cells, the blood is less and less able to carry out its life-sustaining functions. More than 44,000 people in the United States are diagnosed with leukemia each year. Leukemia Risk Factors Leukemia Warning Signs Leukemia Detection, Diagnosis and Staging Leukemia Treatment Other Links: Stem Cells Stem Cell Transplant / Bone Marrow Transplant Transplant Candidates What Are Stem Cells? The Stem Cell Transplant Process The Stem Cell Transplant Team Download Patient Handbook (PDF) Frequently Asked Questions Contact Us