Childhood Acute Myeloid Leukemia/Other Myeloid Malignancies Treatment (PDQ®): Treatment - Health Professional Information [NCI] - Classification of Pediatric Myeloid Malignancies
Table 2. Acute Leukemias of Ambiguous Lineage According to the WHO Classification of Tumors of Hematopoietic and Lymphoid Tissuesa continued...
Classification of Myelodysplastic Syndromes in Children
The FAB classification of myelodysplastic syndromes (MDS) is not completely applicable to children.[155,156] In adults, MDS is divided into several distinct categories based on the presence of myelodysplasia, types of cytopenia, specific chromosomal abnormalities, and the percentage of myeloblasts.[156,157,158,159]
A modified classification schema for MDS and myeloproliferative disorders (MPDs) was published by WHO in 2008. The primary WHO classification includes:
WHO classification of MDS
- Refractory cytopenia with unilineage dysplasia:
- Refractory anemia with ring sideroblasts.
- Refractory cytopenia with multilineage dysplasia.
- Refractory anemia with excess blasts.
- MDS with isolated del (5q).
- MDS, unclassifiable.
- Childhood MDS:
- Provisional entity: Refractory cytopenia of childhood.
Refractory cytopenia of childhood is noted to be reserved for children with MDS who have less than 2% blasts in their peripheral blood and less than 5% blasts in their bone marrow along with persistent cytopenia(s) and dysplasia. It is also noted in the new WHO classification that refractory cytopenia of childhood, unlike MDS in adults, is usually characterized by bone marrow hypocellularity, making the distinction with aplastic anemia and bone marrow failure syndromes often difficult.
WHO classification of myelodysplastic/myeloproliferative neoplasms
- Chronic myelomonocytic leukemia (CMML).
- Atypical chronic myeloid leukemia, BCR-ABL1 negative (aCML).
- Juvenile myelomonocytic leukemia (JMML).
- Myelodysplastic/myeloproliferative neoplasm, unclassifiable.
WHO classification of myeloid and lymphoid neoplasms with eosinophilia and abnormalities of PDGFRA, PDGFRB, or FGFR1
- Myeloid and lymphoid neoplasms with PDGFRA rearrangement.
- Myeloid neoplasms with PDGFRB rearrangement.
- Myeloid and lymphoid neoplasms with FGFR1 abnormalities.
The peripheral blood and bone marrow findings for the myelodysplastic syndromes according to the 2008 WHO classification schema  are summarized in Table 3.
Table 3. World Health Organization (WHO) Peripheral Blood and Bone Marrow Findings for Myelodysplastic Syndromes (MDS)
|RCUD (including RA, RN and RT)||RARS||RCMD||RAEB-1||RAEB-2||MDS-U||del(5q)|
|EP = erythroid precursors; MDS-U = myelodysplastic syndromes, unclassifiable; ML = multilineage; RA = refractory anemia; RAEB = refractory anemia with excess blasts; RARS = refractory anaemia with ring sideroblasts; RCMD = refractory cytopenia with multilineage dysplasia; RCUD = refractory cytopenia with unilineage dysplasia; RN = refractory neutropenia; RT = refractory thrombocytopenia; UL = unilineage.|
|a Bicytopenia may occasionally be observed. Cases with pancytopenia should be classified as MDS-U.|
|b When accompanied by cytogenetic abnormality considered as presumptive evidence for a diagnosis of MDS.|
|c Cases with Auer rods and <5% myeloblasts in the blood and <10% in the marrow should be classified as RAEB-2.|
|d If the marrow myeloblast percentage is <5% but there are 2%–4% myeloblasts in the blood, the diagnostic classification is RAEB-1. Cases of RCUD and RCMD with 1% myeloblasts in the blood should be classified as MDS-U.|
|Cytopenia(s)||Unicytopenia or bicytopeniaa|| ||+||+||+||+|| |
|Anemia|| ||+|| || || || ||+|
|Platelets|| || || || || || ||Normal to increased|
|Marrow dysplasia|| || || ||UL or ML||UL or ML|| || |
| ||erythroid|| ||+|| || || || || |
| ||myeloid||≥10% in 1 myeloid lineage|| ||≥10% in ≥2 myeloid lineages|| || ||<10% in ≥1 myeloid lineageb|| |
| ||megakaryocytic|| || || || || || ||Normal to increased with hypolobulated nuclei|
|Auer's rods (blood and/or bone marrow)|| || ||None||None||±c|| ||None|
|Ringed sideroblasts||<15% of EP||≥15% of EP||± 15%|| || || || |
|Peripheral blasts||Rare or none (<1%)d||None||Rare or none (<1%)d||<5%d||5%–19%||(≤1%)d||Rare or none (<1%)|
|Bone marrow blasts||<5%||<5%||<5%||5%–9%d||10%–19%||<5%||<5%|
|Peripheral monocytes|| || ||<1 x 109 /L||<1 x 109 /L||<1 x 109 /L|| || |
|Cytogenetic abnormality|| || || || || || ||Isolated del(5q)|