Table 1.

The Evolving Classification of MDS

FAB 1982	WHO 2001	WHO 2008	Blasts	Other Findings	Cytogenetic abnormalities
RA	RA	RCUD RA RN RT	<1% PB** <5% BM	Uni or bi-lineage dysplasia* <15% RS	25%
RARS	RARS	RARS	None in PB, <15% BM	At least 15% RS	10%
	RCMD RCMD-RS	RCMD (−RS)	<1% PB*** <5% BM	Dysplasia >10% in 2 cell lines, +/− RS, no AR****	50%
RAEB	RAEB-1	RAEB-1	<5% PB 5–9% BM	Cytopenia, <1K/ul mono; dysplasia in 1 or more lines, no AR****	50–70%
	RAEB-2	RAEB-2	5–19% 10–19 BM	Cytopenia, <1K/uL mono, +/− AR; dysplasia in 1 or more lines	50–70%
		MDS-U	<1% PB; <5% BM	Cytopenia, <10% dysplasia; cytogenetic abnormalities present	50%
		MDS with 5q	<1% PB <5% BM	Anemia, nml or incr. platelets, isolated del(5q), hypo-lobated megakaryocytes, no AR	100%
RAEB-T			20–29% BM
CMML

Stipulations:

^*If pancytopenia present, change to MDS-U;

^**If 1% blasts present, change to MDS-U;

^***if 2–4% PB blasts present, upgrade to RAEB-1;

^****if AR present, upgrade to RAEB-2.

Abbreviations: FAB, French American British classification; WHO, World Health Organization classification; RA, Refractory Anemia; RARS, Refractory Anemia with Ring Sideroblasts; RAEB, Refractory Anemia with Excess Blasts; RAEB-T, Refractory Anemia with Excess Blasts in Transformation; CMML, Chronic Myelomonocytic Leukemia; AML, Acute Myeloid Leukemia; RCMD, Refractory Cytopenia with Multi-lineage Dysplasia; RCUD, Refractory Cytopenia with Uni-lineage Dysplasia; MDS-U, Myelodysplastic syndrome-unclassified; AR, Auer Rods; PB, peripheral blood; BM, bone marrow; RS, ring sideroblasts (% indicates percent RS of total nucleated erythroid precursors).

Bold text indicates the current classification.