Acute Myeliod Leukemia:

Acute myeloid leukemia: Lineage determination

Acute leukemia is determined to be myeloid if it fulfils one of the following criteria and does not fulfil the criteria to diagnose acute leukemia of ambiguous lineage (see the part for acute leukemia of ambiguous lineage).

1. Positive for MPO

  • According to WHO classification, MPO is considered as positive if ≥ 3% blasts are positive by MPO or Sudan black B cytochemical stains.
  • WHO classification does not provide a cut-off for MPO by flow cytometric analysis.
  • According to EGIL (European Group for the Immunological Characterization of Leukemias), ≥ 10% blasts need to be positive by flow cytometric analysis compared to an isotype control (see Fig 1).

2. Presence of Auer rods

3. If MPO is negative, express ≥ 2 myeloid-associated markers including CD13, CD33 and CD117.

4. Express ≥ 2 monocytic markers including non-specific esterase (NSE), CD11c, CD14, CD64 and lysozyme.

Fig 1. Determination of MPO expression


Fig. 1A: Blasts (red) negative for MPO or lymphocytes (dark blue; appear to be purple) can be used as negative control to establish negative threshold for MPO expression. Blasts negative for MPO are preferred since lymphocytes are usually smaller than blasts. Granulocytes (brown) can be used as positive control.


Fig. 1B: Blasts (red) positive for MPO.

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