Leukemia is a cancer of the blood-forming tissues (hematopoietic tissues: myeloid tissue and lymphoid tissue) of the body, including the lymphatic system, and bone marrow. The disease results from an excessive production of abnormal white blood cells in the body. This anarchic excessive number of white blood cells can be immature, acute leukemia; or mature, chronic leukemia. Leukemia cells cannot fight infection effectively and can interfere with the production of red blood cells (which carry oxygen) and the platelets (which control bleeding).
Normally, white blood cells play an important role in the natural defense system of the body. They attack foreign bodies or pathogenic entities, such as viruses and bacteria, in order to destroy them and keep the organism healthy. They are produced in the bone marrow, spongy center of certain bones: hip and thigh bones for instance. Without healthy, functioning white blood cells, the body may develop serious and sometimes fetal infections.
Types of Leukemia
Generally, leukemia can be acute or chronic
Acute leukemia occurs within a few days or weeks, and results in the accumulation of a large number of immature, undeveloped cells called blasts. These cells cannot function properly like normal white blood cells, which poses a high risk of infection for people with acute leukemia. Moreover, since the body is engaged in producing blasts, it does not make enough red blood cells or platelets, which can cause anemia or bleeding disorders.
The two main types of acute leukemia are acute lymphoblastic leukemia (ALL) and acute myelogenous leukemia (AML).
Chronic leukemia affects the hematopoietic system and progresses more slowly, over a period of months or years. It is characterized by the overproduction of mature white blood cells that cannot function normally.
The two main types of chronic leukemia are chronic lymphocytic leukemia (CLL) and chronic myeloid leukemia (CML).
The most common leukemias in adults are AML and CLL. There are many different subcategories though.
Acute lymphoblastic leukemia (ALL) – this form of blood cancer is the most common in children. It results from an abnormal reproduction and uncontrolled accumulation of immature lymphocytes, white blood cells. This causes an abundance of immature lymphocytes in the body which interfere with the production of red blood cells as well as platelets. For more info, please visit our acute lymphoblastic leukemia (ALL) section.
Chronic lymphocytic leukemia (CLL) – this cancer is almost always diagnosed in people over 55 years. This is the most common form of leukemia overall, and affects about twice as many men as women. CLL progresses slower than the ALL. But without treatment, gradually, the leukemic cells will outnumber normal cells, including bone marrow where other blood cells are produced, making survival more difficult. For additional information, please see chronic lymphocytic leukemia (CLL).
Acute myeloid leukemia (AML) – this form of leukemia most commonly affects adults. It is characterized by an uncontrolled growth and accumulation of a type of immature blood cells found in the bone marrow called myeloblasts. This disorder disrupts the function of red blood cells, platelets, and normal white blood cells. See acute myeloid leukemia (AML)
Chronic myeloid leukemia (CML) – this type occurs more rarely than AML and has less effects on the production of other types of cells. The risks of suffering from CML are very low in children but increase with age. CML is associated with the Philadelphia chromosome, a chromosomal disorder resulting from the exchange of portions of genetic material from chromosomes 9 and 22. See chronic myelogenous leukemia (CML) for more info.
Thefreedictionary.com – McGraw-Hill Dictionary of Scientific & Technical Terms, 6E: hematopoietic tissue
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