Most cases of AML are diagnosed by examining a sample of blood. This shows immature leukaemia cells. White cell counts in the blood are often higher than normal due to the increased number of immature leukaemia cells.
However, examination of a bone marrow sample is the most important test for diagnosing AML. Diagnosis requires that more than 20% of the white blood cells in the bone marrow be leukaemia cells (Dohner et al 2017).
The immature leukaemia cells are slightly larger and less well differentiated (Figure 4a) than normal white blood cells (Figure 4b).
Figure 4a Immature myeloid leukaemia cells in bone marrow in AML
Credit: Gamal Abdul Hamid (ResearchGate)
Figure 4b Normal white blood cells