What Are Leukemia and Myelodysplastic Syndromes

In a healthy person, the bone marrow makes all of the cells that make up blood.  This includes: 1) red blood cells that carry oxygen to all tissues in the body; 2) platelets that help form blood clots to prevent bleeding; and 3) white blood cells to fight infection.  White blood cells are further divided into two major types: myeloid cells (e.g., neutrophils and monocytes) that help fight bacterial infections and lymphocytes that help fight viral infections.


The word leukemia comes from 2 Greek words:  leukos meaning white and haimameaning blood.  Patients with leukemia have an unusually high proportion of white blood cells  (leukocytes) in their circulation.  It is often simply referred to as “blood cancer”. For more information about leukemia, please check the following website from the National Cancer Institute. https://www.cancer.gov/types/leukemia

Types of Leukemia

Leukemia is classified into four major subgroups.  Your doctors will perform of series of tests to determine what type of leukemia you have.

  • Acute myeloid leukemia (AML):  An aggressive (fast growing) type of leukemia in which there are too many immature myeloid cells (myeloid blasts) in the blood and bone marrow.
  • Acute lymphocytic leukemia (ALL): An aggressive type of leukemia in which there are too many immature lymphoid cells (lymphoid blasts) in the blood and bone marrow.
  • Chronic myeloid leukemia (CML): A more indolent (slow growing) type of leukemia in which too many myeloid cells are made.  Leukemic blasts only make up a small percentage of this cancer type.
  • Chronic lymphocytic leukemia (CLL).  Another indolent type of leukemia in which mostly mature lymphocytes accumulate in the blood and bone marrow.  Enlargement of lymph nodes is common in this type of cancer.

Myelodysplastic syndrome (MDS) 

A MDS is a type of cancer in which the bone marrow is unable to produce normal levels of one or more type of blood cell.  Thus, patients with a MDS may initially seek medical help for symptoms of anemia (a result of too few red blood cells), bleeding (due to too few platelets), or recurrent infection (a consequence of a poorly functioning immune system resulting from too few white blood cells).  MDS is classified into different subtypes based on the percentage of leukemic blasts in the blood and other clinically detectable abnormalities in the bone marrow.  For more information about MDS, please check the following website from the National Cancer Institute. http://www.cancer.gov/cancertopics/pdq/treatment/myelodysplastic/patient

Developing a treatment plan

The leukemia program at the Siteman Cancer Center is recognized as one of the top leukemia programs in the world.  Your doctors will first order a series of genetic and other tests of your blood and bone marrow to classify your leukemia/MDS.  Based on this information, your doctors will develop a cutting edge treatment plan that is right for you and your type of leukemia/MDS.