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For most types of cancer, figuring out the stage (extent) of the cancer is very important. The stage is based on the size of the tumor and how far it has spread. But leukemia is not staged this way because it does not usually form a tumor. It already involves all the bone marrow and, in many cases, it has also spread to other organs. So the outlook for the patient with acute myeloid leukemia (AML) depends on other things, such as the exact type of AML, the age of the patient, and lab test results.

Classification systems

Two systems have been used to classify AML into subtypes: the French-American-British (FAB) system and the newer World Health Organization (WHO) system.

The French-American-British (FAB) classification of AML

In the 1970s, a group of French, American, and British leukemia experts divided AML into subtypes, M0 through M7, based on the type of cell from which the leukemia started and how mature the cells are. This system is based largely on how the leukemia cells looked under the microscope. But now doctors use many advanced gene tests to classify AML.

World Health Organization (WHO) Classification of AML

The FAB system is useful and is still often used to group AML into subtypes. But it doesn’t take into account many of the factors now known to affect a person’s outlook. The World Health Organization (WHO) has developed a newer system that includes some of these factors to try to help better classify cases of AML.

Prognostic factors

In recent years, research has focused on why some patients have a better chance to be cured than others. Differences among patients that affect how they respond to treatment are called prognostic factors. These factors include:

  • The patient’s age
  • White blood cell count
  • Whether the leukemia cells have certain gene or chromosome changes
  • Whether the person had a blood disorder before the AML
  • Whether the person had chemotherapy or radiation in the past to treat another cancer
  • Whether the AML has reached the brain and spinal cord
  • How well and (how quickly) the AML responds to treatment

If you would like more details about these prognostic factors, see Leukemia: Acute Myeloid (Myelogenous).

Last Medical Review: 04/21/2015
Last Revised: 02/22/2016