Classification of myelodysplastic syndromes (MDS)

WHO classification of myelodysplasia

CategoryPeripheral bloodBone marrow
RCUD
(RA, RN or RT)
Anemia, neutropenia or thrombocytopenia (1)
No or rare blasts (< 1%) (2)
Dysplasia in ≥ 10% of cells in one myeloid lineage
< 5% blasts
< 15% of erythroid cells are ringed sideroblasts
RARSAnemia
No blasts
Erythroid dysplasia only
≥ 15% of erythroid cells are ringed sideroblasts
< 5% blasts
RCMDBi- or pancytopenia
No or rare blasts (< 1%) (3)
No Auer rods
< 1 x109/L monocytes
Dysplasia in > 10% of cells in 2 or more myeloid cell lines
< 5% blasts
No Auer rods
RAEB-1Cytopenia(s)
< 5% blasts
No Auer rods
< 1 x 109/L monocytes
Uni- or multilineage dysplasia
5-9% blasts (4)
No Auer rods
RAEB-2Cytopenia(s)
5%-19% blasts (5)
Auer rods may be present (6)
< 1 x109/L monocytes
Uni- or multilineage dysplasia
10-19% blasts (7)
Auer rods may be present (8)
MDS-UCytopenias
No or rare blasts (< 1%)
No Auer rods
Unequivocal dysplasia in < 10% of cells of one or more myeloid lineages AND cytogenetic abnormality consistent with MDS (9)
< 5% blasts
No Auer rods
5q- syndromeAnemia
No or rare blasts
Platelets usually normal or increased
Normal to increased megakaryocytes with hypolobulated nuclei
< 5% blasts
No Auer rods
Isolated del(5q)

Notes:
(1) Bicytopenia may be observed. Cases with pancytopenia should be classified as MDS-U
(2) If marrow blasts are < 5% but there are 2 - 4% blasts in peripheral blood, classify as RAEB-1 (3) If marrow blasts are < 5% but there are 2 - 4% blasts in peripheral blood, classify as RAEB-1 (4) Cases of RCUD and RCMD with marrow blasts < 5% but 2 - 4% blasts in peripheral blood are also classified as RAEB-1 (5) Peripheral blood blast percentage may be lower if marrow blast criteria are met, or if Auer rods are present
(6) Cases with peripheral blood Auer rods are classified as RAEB-2 irrespective of blast percentage
(7) Cases with lower marrow blast percentage are classified as RAEB-2 if the peripheral blood blast criteria are met, or if Auer rods are present
(8) Cases with marrow Auer rods are classified as RAEB-2 irrespective of blast percentage
(9) Recurring cytogenetic abnormalities considered evidence for MDS in patients with persistent unexplained cytopenias, but in the absence of definite morphological features of MDS:

  • -7 or del(7q)
  • -5 or del(5q)
  • i(17q) or t(17p)
  • -13 or del(13q)
  • del(11q)
  • del(12p) or t(12p)
  • del(9q)
  • idic(X)(q13)
  • t(11;16)(q23;p13.3)
  • t(3;21)(q26.2;q22.1)
  • t(1;3)(p36.3;q21.1)
  • t(2;11)(p21;q23)
  • inv(3)(q21;q26.2)
  • t(6;9)(p23;q34)

This classification of myelodysplasia (myelodysplastic syndrome, MDS) in adults was published in the 4th edition of the World Health Organisation book, “WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues” in 2008.1

MDS: myelodysplastic syndrome
MDS-U: Myelodysplastic syndrome, unclassified
RA: refractory anemia
RAEB-1: refractory anaemia with excess blasts-1
RAEB-2: refractory anaemia with excess blasts-2
RARS: refractory anemia with ringed sideroblasts
RCMD: refractory cytopenia with multilineage dysplasia
RCUD: refractory cytopenia with unilineage dysplasia
RN: refractory neutropenia
RT: refractory thrombocytopenia
WHO: World Health Organisation