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Most people diagnosed with AML have one of eight different kinds (subtypes) of AML. It's important to know your subtype because it plays a large part in determining the type of treatment you'll receive. Doctors often use one of two systems to classify subtypes: the French, American, British (FAB) system or the World Health Organization (WHO) classification system.

FAB Classification

FAB subtypes are based on how much the leukemic cells have matured and the type of blood cell the disease developed from. AML cells can have features of red cells, platelets, white cells (monocytes, eosinophils or, rarely, basophils or mast cells) and immature white cells (myeloblasts or promyelocytes).

Unlike staging - used mostly to designate the severity of cancers when a solid tumor is present - the number assigned to the subtype has nothing to do with how far along the cancer has advanced. The subtype is named after the dominant cells found, such as acute erythroid leukemia, acute megakaryocytic leukemia, acute monocytic leukemia.

Treatment is similar for most of these subtypes except M3 - acute promyelocytic leukemia.

The table below shows the FAB subtypes used by many doctors.

Classification

Cell Type Most Affected

Description

M0 Myeloblastic Minimally differentiated AML
M1 Myeloblastic, with minimal maturation Myeloblasts are the dominant leukemic cells in the marrow at the time of diagnosis
M2 Myeloblastic, with maturation Many myeloblasts are present, but some cells are developing toward fully formed blood cells
M3 Promyelocytic
(acute promyelocytic leukemia)
Leukemic cells have a translocation between chromosomes 15 and 17
M4 Myelomonocytic
(acute myelomonocytic leukemia)
Leukemic cells often have an inversion of chromosome 16
M5 Monocytic
(acute monocytic leukemia)
Leukemic cells have features of developing monocytes (white cells)
M6 Erythroleukemic
(acute erythroid leukemia)
Leukemic cells have features of developing red cells
M7 Megakaryocytic
(acute megakaryocytic leukemia)
Leukemic cells have features of developing platelets

WHO Classification

Another system sometimes used by doctors is the WHO classification system. It divides AML into several broad groups based on expected outcomes. WHO classifications for AML include:

  • AML with recurrent genetic abnormalities
  • AML with myelodysplasia-related changes
  • therapy-related AML
  • AML not otherwise specified
  • AML with a translocation between chromosomes 8 and 21
  • AML with a translocation or inversion in chromosome 16
  • AML with changes in chromosome 11
  • acute promyelocytic leukemia, which usually has a translocation between chromosomes 15 and 17
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last updated on Thursday, May 17, 2012
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