Table 9 Differentiation markers and criteria for acute myeloid leukaemia (AML) types defined by differentiation.

From: The 5th edition of the World Health Organization Classification of Haematolymphoid Tumours: Myeloid and Histiocytic/Dendritic Neoplasms

Type

Diagnostic criteria*

AML with minimal differentiation

• Blasts are negative (<3%) for MPO and SBB by cytochemistry

• Expression of two or more myeloid-associated antigens, such as CD13, CD33, and CD117

AML without maturation

• ≥3% blasts positive for MPO (by immunophenotyping or cytochemistry) or SBB and negative for NSE by cytochemistry

• Maturing cells of the granulocytic lineage constitute <10% of the nucleated bone marrow cells

• Expression of two or more myeloid-associated antigens, such as MPO, CD13, CD33, and CD117

AML with maturation

• ≥3% blasts positive for MPO (by immunophenotyping or cytochemistry) or SBB by cytochemistry

• Maturing cells of the granulocytic lineage constitute ≥10% of the nucleated bone marrow cells

• Monocyte lineage cells constitute < 20% of bone marrow cells

• Expression of two or more myeloid-associated antigens, such as MPO, CD13, CD33, and CD117

Acute basophilic leukemia

• Blasts & immature/mature basophils with metachromasia on toluidine blue staining

• Blasts are negative for cytochemical MPO, SBB, and NSE

• No expression of strong CD117 equivalent (to exclude mast cell leukemia)

Acute myelomonocytic leukaemia

• ≥20% monocytes and their precursors

• ≥20% maturing granulocytic cells

• ≥3% of blasts positive for MPO (by immunophenotyping or cytochemistry)

Acute monocytic leukaemia

• ≥80% monocytes and/or their precursors (monoblasts and/or promonocytes)

• <20% maturing granulocytic cells

• Blasts and promonocytes expressing at least two monocytic markers including CD11c, CD14, CD36 and CD64, or NSE positivity on cytochemistry

Acute erythroid leukaemia

• ≥30% immature erythroid cells (proerythroblasts)

• Bone marrow with erythroid predominance, usually ≥80% of cellularity

Acute megakaryoblastic leukaemia

• Blasts express at least one or more of the platelet glycoproteins: CD41 (glycoprotein llb), CD61 (glycoprotein IIIa), or CD42b (glycoprotein lb)b

  1. *Shared diagnostic criteria include:
  2.      -  ≥20% blasts in bone marrow and/or blood (except for acute erythroid leukaemia).
  3.      -  Criteria for AML types with defined genetic alterations are not met.
  4.      -  Criteria for mixed-phenotype acute leukaemia are not met (relevant for AML with minimal differentiation).
  5.      -  Not fulfilling diagnostic criteria for myeloid neoplasm post cytotoxic therapy.
  6.      -  No prior history of myeloproliferative neoplasm.
  7. BM bone marrow, MPO myeloperoxidase, NSE nonspecific esterase, PB peripheral blood, SBB Sudan Black B.
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