M1

Blasts>=90% of NEC;

>=3% of blasts positive for peroxidase or SBB;

Monocytic component <=10% of NEC;

Granulocytic component <=10% of NEC

(AML with granulocytic maturation)

Blasts 30-89% of NEC;

Granulocytic component >10% of NEC;

Monocytic component <20% of NEC

M3 variant

Characteristic morphology

(Acute myelomonocytic leukaemia)

Blasts >=30% of NEC;

Granulocytic component (including myeloblastc)>=20% of NEC

BM monocytic component >=20% of NEC and

PB monocyte count >=5x10e9/L

BM monocytic component>=20% of NEC and

lysozyme elevated*

BM monocytic component >=20% of NEC and

cytochemical confirmation of monocyte component in BM**

BM resembling M2 but PB monocyte count >= 5x10e9/L and

lysozyme elevated

BM resembling M2 but PB monocyte count >= 5x10e9/L and

cytochemical demonstration of monocytic component in BM

(acute monocytic monoblastic leukaemia)

(without maturation or acute monoblastic leukaemia)

Monocytic component >= 80% of NEC;

Monoblasts >= 80% monocytic component

(with maturation or acute monocytic leukaemia)

Monocytic component >= 80% of NEC;

Monoblasts < 80% of monocyte component

(erythroleukaemia)

Erythroblasts >= 50%;

blasts >= 30% of NEC

(megakaryoblastic leukaemia)

Blasts demonstrated to be megakaryoblasts, for example by ultrastructural cytochemistry showing the presence of platelet peroxidase or by immunological cell marker studies showing the presence of platelet antigens

(AML with minimal evidence of myeloid differentiation)

Peroxidase and SBB positive in < 3% of blasts but

blasts demonostrated to be myeloid by immunophenotyping