The 5th edition of the World Health Organization (WHO) classification of haematolymphoid tumours: myeloid and histiocytic/dendritic neoplasms introduces the term myelodysplastic neoplasms (MDS) to replace myelodysplastic syndromes and categorises MDS based on defining genetic abnormalities or morphology. (1)
MDS with defining genetic abnormalities
MDS with low blasts and isolated 5q deletion (MDS-5q)
- Blasts: <5% in bone marrow and <2% in peripheral blood
- Cytogenetics: 5q deletion alone, or with one other abnormality other than monosomy 7 or 7q deletion.
MDS with low blasts and SF3B1 mutation (MDS-SF3B1)
- Blasts: <5% in bone marrow and <2% in peripheral blood
- Cytogenetics: absence of 5q deletion, monosomy 7, or complex karyotype
- Mutations: SF3B1 (≥15% ring sideroblasts may substitute for SF3B1 mutation).
MDS with biallelic TP53 inactivation (MDS-biTP53)
- Blasts: <20% in bone marrow and peripheral blood
- Cytogenetics: usually complex
- Mutations: two or more TP53 mutations, or one mutation with evidence of TP53 copy number loss or copy neutral loss of heterozygosity.
MDS, morphologically defined
MDS with low blasts (MDS-LB)
- Blasts: <5% in bone marrow and <2% in peripheral blood.
MDS, hypoplastic (MDS-h)
- Blasts: <5% in bone marrow and <2% in peripheral blood
- Bone marrow cellularity ≤25% (age adjusted).
MDS with increased blasts (MDS-IB)
MDS-IB1
- Blasts: 5% to 9% in bone marrow or 2% to 4% in peripheral blood.
MDS-IB2
- Blasts: 10% to 19% in bone marrow or 5% to 19% in peripheral blood or Auer rods.
MDS with fibrosis (MDS-f)
- Blasts: 5% to 19% in bone marrow; 2% to 19% in peripheral blood.
Reference:
- Khoury JD, Solary E, Abla O, et al. The 5th edition of the World Health Organization classification of haematolymphoid tumours: myeloid and histiocytic/dendritic neoplasms. Leukemia. 2022 Jul;36(7):1703-19.