2008 World Health Organization classification of myelodysplastic syndromes/neoplasms (Swerdlow et al3 pp. 87–107).
| Comments: If peripheral blood blasts are 2% to 4%, the diagnosis is RAEB-1 even if marrow blasts are less than 5%. If Auer rods are present, the WHO considers the diagnosis RAEB-2 if the blast proportion is less than 20% (even if less than 10%), AML if at least 20% blasts. For all subtypes, peripheral blood monocytes are less than 1 × 109/L. Bicytopenia may be observed in RCUD subtypes, but pancytopenia with unilineage marrow dysplasia should be classified as MDS-U. Therapy-related MDS (t-MDS), whether due to alkylating agents, topoisomerase II inhibitors, or radiation, is classified together with therapy-related acute myeloid leukemia (t-MDS/t-AML) in the WHO classification of AML and precursor lesions. The listing in this table excludes MDS/myeloproliferative neoplasm overlap categories, such as chronic myelomonocytic leukemia, juvenile myelomonocytic leukemia, and the provisional entity RARS with thrombocytosis. | ||||
| Name | Abbreviation | Peripheral blood: key features | Bone marrow: key features | WHO-estimated proportion of pts with MDS |
| Refractory cytopenias with unilineage dysplasia (RCUD): | ||||
| refractory anemia | RA | Anemia < 1% blasts | Unilineage erythroid dysplasia (in ≥ 10% of cells) < 5% blasts | 10%–20% |
| refractory neutropenia | RN | Neutropenia < 1% blasts | Unilineage granulocytic dysplasia < 5% blasts | < 1% |
| refractory thrombocytopenia | RT | Thrombocytopenia < 1% blasts | Unilineage megakaryocytic dysplasia < 5% blasts | < 1% |
| Refractory anemia with ring sideroblasts | RARS | Anemia No blasts | Unilineage erythroid dysplasia ≥ 15% of erythroid precursors are ring sideroblasts. < 5% blasts | 3%–11% |
| Refractory cytopenias with multilineage dysplasia | RCMD | Cytopenia(s) < 1% blasts No Auer rods | Multilineage dysplasia ± ring sideroblasts < 5% blasts No Auer rods | 30% |
| Refractory anemia with excess blasts, type 1 | RAEB-1 | Cytopenia(s) < 5% blasts No Auer rods | Unilineage or multilineage dysplasia 5%–9% blasts No Auer rods | 40% |
| Refractory anemia with excess blasts, type 2 | RAEB-2 | Cytopenia(s) 5%–19% blasts ± Auer rods | Unilineage or multilineage dysplasia 10%–19% blasts ± Auer rods | |
| MDS associated with isolated del(5q) | Del(5q) | Anemia Normal or high platelet count < 1% blasts | Isolated 5q31 chromosome deletion Anemia, hypolobated megakaryocytes < 5% blasts | Uncommon |
| Childhood MDS, including refractory cytopenia of childhood (provisional) | RCC | Pancytopenia | < 5% marrow blasts for RCC Marrow usually hypocellular | <1% |
| MDS, unclassifiable | MDS-U | Cytopenias ≤ 1% blasts | Does not fit other categories Dysplasia and < 5% blasts If no dysplasia, MDS-associated karyotype | ? |
| Comments: If peripheral blood blasts are 2% to 4%, the diagnosis is RAEB-1 even if marrow blasts are less than 5%. If Auer rods are present, the WHO considers the diagnosis RAEB-2 if the blast proportion is less than 20% (even if less than 10%), AML if at least 20% blasts. For all subtypes, peripheral blood monocytes are less than 1 × 109/L. Bicytopenia may be observed in RCUD subtypes, but pancytopenia with unilineage marrow dysplasia should be classified as MDS-U. Therapy-related MDS (t-MDS), whether due to alkylating agents, topoisomerase II inhibitors, or radiation, is classified together with therapy-related acute myeloid leukemia (t-MDS/t-AML) in the WHO classification of AML and precursor lesions. The listing in this table excludes MDS/myeloproliferative neoplasm overlap categories, such as chronic myelomonocytic leukemia, juvenile myelomonocytic leukemia, and the provisional entity RARS with thrombocytosis. | ||||
| Name | Abbreviation | Peripheral blood: key features | Bone marrow: key features | WHO-estimated proportion of pts with MDS |
| Refractory cytopenias with unilineage dysplasia (RCUD): | ||||
| refractory anemia | RA | Anemia < 1% blasts | Unilineage erythroid dysplasia (in ≥ 10% of cells) < 5% blasts | 10%–20% |
| refractory neutropenia | RN | Neutropenia < 1% blasts | Unilineage granulocytic dysplasia < 5% blasts | < 1% |
| refractory thrombocytopenia | RT | Thrombocytopenia < 1% blasts | Unilineage megakaryocytic dysplasia < 5% blasts | < 1% |
| Refractory anemia with ring sideroblasts | RARS | Anemia No blasts | Unilineage erythroid dysplasia ≥ 15% of erythroid precursors are ring sideroblasts. < 5% blasts | 3%–11% |
| Refractory cytopenias with multilineage dysplasia | RCMD | Cytopenia(s) < 1% blasts No Auer rods | Multilineage dysplasia ± ring sideroblasts < 5% blasts No Auer rods | 30% |
| Refractory anemia with excess blasts, type 1 | RAEB-1 | Cytopenia(s) < 5% blasts No Auer rods | Unilineage or multilineage dysplasia 5%–9% blasts No Auer rods | 40% |
| Refractory anemia with excess blasts, type 2 | RAEB-2 | Cytopenia(s) 5%–19% blasts ± Auer rods | Unilineage or multilineage dysplasia 10%–19% blasts ± Auer rods | |
| MDS associated with isolated del(5q) | Del(5q) | Anemia Normal or high platelet count < 1% blasts | Isolated 5q31 chromosome deletion Anemia, hypolobated megakaryocytes < 5% blasts | Uncommon |
| Childhood MDS, including refractory cytopenia of childhood (provisional) | RCC | Pancytopenia | < 5% marrow blasts for RCC Marrow usually hypocellular | <1% |
| MDS, unclassifiable | MDS-U | Cytopenias ≤ 1% blasts | Does not fit other categories Dysplasia and < 5% blasts If no dysplasia, MDS-associated karyotype | ? |