What is the World Health Organization (WHO) classification of myelodysplastic syndromes (MDS)?

Updated: Oct 18, 2019
  • Author: Matthew C Foster, MD; Chief Editor: Emmanuel C Besa, MD  more...
  • Print
Answer

Answer

The WHO classification system of MDS relies on incorporating clinical features, peripheral blood and bone marrow findings, and cytogenetic analysis. [1] This classification also includes a collection of heterogeneous neoplasms that share features of MDS and myeloproliferative neoplasms.

These "overlap syndromes" fall under the classification "myelodysplastic/myeloproliferative neoplasms" (MDS/MPN) and include the following:

  • Chronic myelomonocytic leukemia (CMML-1 and CMML-2)
  • Atypical chronic myeloid leukemia (aCML), BCR-ABL1 negative
  • Juvenile myelomonocytic leukemia (JMML)
  • MDS/MPN with ring sideroblasts and thrombocytosis (MDS/MPN-RS-T)
  • MDS/MPN, unclassifiable

Although a detailed discussion of the overlap disorders is beyond the scope of this review, they share clinical, pathologic, and therapeutic features with MDS and can be treated similarly when they present with more features of MDS than MPN.

The WHO MDS classification comprises the following:

  • MDS with single-lineage dysplasia
  • MDS with ring sideroblasts (MDS-RS):
  • MDS-RS and single-lineage dysplasia
  • MDS-RS and multilineage dysplasia
  • MDS with multilineage dysplasia:
  • MDS with excess blasts–1 (MDS-EB–1)
  • MDS with excess blasts–2 (MDS-EB–2)
  • MDS associated with isolated del(5q)
  • MDS, unclassifiable (MDS-U)
  • Refractory cytopenia of childhood
  • Myeloid neoplasms with germ line predisposition 
  • Therapy-related MDS (t-MDS)

See Table 1, below.

Table 1. World Health Organization criteria for myelodysplastic syndromes (Open Table in a new window)

Syndrome

Dysplastic lineages 

Cytopenias* 

Ring sideroblasts as % of marrow erythroid elements 

Bone marrow (BM) and peripheral blood (PB) blasts 

Cytogenetics by conventional karyotype analysis 

MDS with single lineage dysplasia (MDS-SLD) 

1 or 2 

< 15%/< 5%† 

BM < 5%

PB < 1%, no Auer rods 

Any, unless fulfills all criteria for MDS with isolated del(5q) 

MDS with multilineage dysplasia (MDS-MLD) 

2 or 3 

1-3 

< 15%/< 5%† 

BM < 5%

PB < 1%, no Auer rods 

Any, unless fulfills all criteria for MDS with isolated del(5q) 

 MDS with ring sideroblasts (MDS-RS) with single lineage dysplasia (MDS-RS-SLD) 

1 or 2 

≥15%/≥5%† 

BM < 5%

PB < 1%, no Auer rods 

Any, unless fulfills all criteria for MDS with isolated del(5q) 

MDS-RS with multilineage dysplasia (MDS-RS-MLD) 

2 or 3 

1-3 

≥15%/≥5%† 

BM < 5%

PB < 1%, no Auer rods 

Any, unless fulfills all criteria for MDS with isolated del(5q) 

MDS with isolated del(5q) 

1-3 

1-2 

None or any 

BM < 5 %

 PB < 1%, no Auer rods 

del(5q) alone or with 1 additional abnormality except −7 or del(7q)

MDS with excess blasts– 1 (MDS-EB-1)

0-3 

1-3 

None or any 

BM 5%-9% or

PB 2%-4%, no Auer rods 

Any 

MDS-EB-2 

0-3 

1-3 

None or any 

BM 10%-19% or

PB 5%-19% or Auer rods 

Any 

MDS, unclassifiable (MDS-U) with 1% blood blasts 

1-3 

1-3 

None or any 

BM < 5%

 PB = 1%,‡ no Auer rods 

Any 

MDS-U with single lineage dysplasia and pancytopenia 

None or any 

BM < 5%

PB < 1%, no Auer rods

Any 

MDS-U based on defining cytogenetic abnormality

1-3 

< 15%§ 

BM < 5%

PB < 1%, no Auer rods 

MDS-defining abnormality 

Refractory cytopenia of childhood 

1-3 

1-3 

None 

BM < 5%

PB < 2% 

Any 

*Cytopenias are defined as: hemoglobin, < 10 g/dL; platelet count, < 100 × 109/L; and absolute neutrophil count, < 1.8 × 109/L. Rarely, MDS may present with mild anemia or thrombocytopenia above these levels. PB monocytes must be < 1 × 109/L

† If SF3B1 mutation is present.

‡ 1% PB blasts must be recorded on at least 2 separate occasions.

Patients with therapy-related MDS have blood and bone marrow findings of one of the above diagnostic categories (frequently with multilineage dysplasia) and a past history of exposure to cytotoxic chemotherapy and/or radiation therapy administered for treatment of cancer or nonneoplastic disease. Erythroid precursors comprise ≥50% of bone marrow nucleated cells. A number of  these patients been shown to have germ line mutations in cancer susceptibility genes; so a careful family history is warranted.

Myeloid neoplasms with germ line predisposition are classified as follows:

  • No preexisting disorder or organ dysfunction - germ line  DDX41 mutation
  • Preexisting platelet disorder - germ line  RUNX1ANKRD26, or  ETV6 mutation
  • Other organ dysfunction - germ line GATA2 mutation; associated bone marrow failure syndromes, telomere biology disorders, or Down syndrome

Did this answer your question?
Additional feedback? (Optional)
Thank you for your feedback!