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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) 
Cytopenia(s) Unicytopenia or bicytopeniaa++++
Anemia ++
Platelets Normal to increased
Marrow dysplasia UL or MLUL 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 rods (blood and/or bone marrow) NoneNone±cNone
Ringed sideroblasts <15% of EP≥15% of EP± 15%
Peripheral blasts Rare or none (<1%)dNoneRare or none (<1%)d<5%d5%–19%(≤1%)dRare or none (<1%)
Bone marrow blasts <5%<5%<5%5%–9%d10%–19%<5%<5%
Peripheral monocytes <1 x 109/L<1 x 109/L<1 x 109/L
Cytogenetic abnormality Isolated 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.
aBicytopenia may occasionally be observed. Cases with pancytopenia should be classified as MDS-U.
bWhen accompanied by cytogenetic abnormality considered as presumptive evidence for a diagnosis of MDS.
cCases with Auer rods and <5% myeloblasts in the blood and <10% in the marrow should be classified as RAEB-2.
dIf 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.