Classifying acute myeloid leukaemia

AML can be divided into subtypes. Different types of AML are treated in different ways. Your doctors need to know which type you have to help them plan the most appropriate treatment for you. For example, acute promyelocytic leukaemia (APL) is a subtype of AML which can affect the way blood clots and is treated differently to other types of AML.

In the UK, doctors usually classify AML according to the World Health Organisation (WHO) system and the French-American-British (FAB) system.

The WHO system

The WHO system classifies AML according to the type of cell that has become abnormal and whether:

  • there are particular chromosomal changes (cytogenetic changes)
  • there are abnormal changes in more than one type of blood cell
  • the leukaemia has developed from a previous blood disorder called myelodysplasia
  • the leukaemia is related to previous cancer treatment (treatment-related AML).

The FAB system

The FAB system looks at the appearance of the leukaemia cells under a microscope (morphology). Each type of AML is named according to the cell type and given a number from M0–M7. For example, the subtype APL mentioned above is M3. Doctors may classify AML with the FAB system while waiting for the results of other tests.

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