Leukemia, commonly known as cancer of the blood, describes a group of malignant disorders that arise in the blood-forming cells. The bone marrow, where the cells of the blood are made, malfunctions to produce abnormal white cells (leukemic cells) in an uncontrolled manner to the detriment of all the other essential blood cells. Blood consists of a clear fluid (plasma), containing chemical substances essential to the body’s needs, and three types of blood cells. The red blood cells (erythrocytes) are by far the most numerous; their main function is to transport oxygen to all the tissues of the body. They contain hemoglobin, an iron-rich protein that gives the blood its red color. A reduction in hemoglobin concentration is known as anemia. The white blood cells, leukocytes, of which there are three major groups, namely monocytes, granulocytes, and lymphocytes, play different roles in defending the body against infection. Platelets help to control bleeding.

Hematopoiesis

Blood cell formation, known as hematopoiesis, starts in the bone marrow, the spongy interior of the large bones, with a pool of immature or undifferentiated cells known as pluripotent stem cells, which contain the characteristics of all the major blood cell lines. These cells divide, either producing themselves exactly or producing more specialized cells that contain the characteristics of only one of the two major cell lines: One of these two specialized cells, known as the mixed myeloid progenitor cell, consists of the progenitor cells to the red blood cells, the monocytes and granulocytes (white cells), and the platelets.