Differences and similarities among the WHO (fifth edition) and ICC classifications
| WHO revised fourth edition . | WHO fifth edition . | ICC . | Differences or similarities . |
|---|---|---|---|
| CNL | CNL Unchanged from 2016 | CNL Similar to WHO revised fourth edition except: Lowering of threshold PB WBC >13 × 109/L if accompanied by CSF3R mutation Defines Accelerated phase as circulating or BM blasts 10%-19% with progressive splenomegaly or worsening thrombocytopenia Blast phase as circulating or BM blasts ≥20% | In the presence of CSF3R mutation–lowering of the PB WBC threshold to >13 × 109/L for diagnosis in ICC Definition of accelerated and blast phase added in ICC |
| CEL, NOS | CEL | CEL, NOS | Both exclude the growing number of tyrosine kinase gene fusions now categorized separately. WHO fifth edition drops the not otherwise specified (NOS) descriptor |
| Myeloid/lymphoid neoplasms with eosinophilia and gene rearrangement | Myeloid/lymphoid neoplasms with eosinophilia and tyrosine kinase gene fusions | Myeloid/lymphoid neoplasms with eosinophilia and tyrosine kinase gene fusions | Both add expanded categories involving JAK2 and FLT3 rearrangements and add ETV6::ABL1 fusion |
| MPN, U | MPN, NOS | MPN-U | Remains unchanged, with only minor terminology adjustments in the WHO fifth edition |
| Atypical CML, BCR-ABL1 negative | MDS/MPN with neutrophilia Same as revised fourth edition but name changed | Atypical CML Essentially unchanged from revised fourth edition except to delete reference to the lack of BCR::ABL1 gene fusion in the name | Significant terminology changes in WHO fifth edition |
| MDS/MPN with ring sideroblasts and thrombocytosis | MDS/MPN with SF3B1 mutation and thrombocytosis | MDS/MPN with thrombocytosis and SF3B1 mutation MDS/MPN with ring sideroblasts and thrombocytosis, NOS | The ICC distinguishes forms carrying the SF3B1 mutation from those without |
| MDS/MPN, U | MDS/MPN, NOS | MDS/MPN, NOS | Remains unchanged, with only minor terminology adjustments in the WHO fifth edition |
| WHO revised fourth edition . | WHO fifth edition . | ICC . | Differences or similarities . |
|---|---|---|---|
| CNL | CNL Unchanged from 2016 | CNL Similar to WHO revised fourth edition except: Lowering of threshold PB WBC >13 × 109/L if accompanied by CSF3R mutation Defines Accelerated phase as circulating or BM blasts 10%-19% with progressive splenomegaly or worsening thrombocytopenia Blast phase as circulating or BM blasts ≥20% | In the presence of CSF3R mutation–lowering of the PB WBC threshold to >13 × 109/L for diagnosis in ICC Definition of accelerated and blast phase added in ICC |
| CEL, NOS | CEL | CEL, NOS | Both exclude the growing number of tyrosine kinase gene fusions now categorized separately. WHO fifth edition drops the not otherwise specified (NOS) descriptor |
| Myeloid/lymphoid neoplasms with eosinophilia and gene rearrangement | Myeloid/lymphoid neoplasms with eosinophilia and tyrosine kinase gene fusions | Myeloid/lymphoid neoplasms with eosinophilia and tyrosine kinase gene fusions | Both add expanded categories involving JAK2 and FLT3 rearrangements and add ETV6::ABL1 fusion |
| MPN, U | MPN, NOS | MPN-U | Remains unchanged, with only minor terminology adjustments in the WHO fifth edition |
| Atypical CML, BCR-ABL1 negative | MDS/MPN with neutrophilia Same as revised fourth edition but name changed | Atypical CML Essentially unchanged from revised fourth edition except to delete reference to the lack of BCR::ABL1 gene fusion in the name | Significant terminology changes in WHO fifth edition |
| MDS/MPN with ring sideroblasts and thrombocytosis | MDS/MPN with SF3B1 mutation and thrombocytosis | MDS/MPN with thrombocytosis and SF3B1 mutation MDS/MPN with ring sideroblasts and thrombocytosis, NOS | The ICC distinguishes forms carrying the SF3B1 mutation from those without |
| MDS/MPN, U | MDS/MPN, NOS | MDS/MPN, NOS | Remains unchanged, with only minor terminology adjustments in the WHO fifth edition |
BM, bone marrow; PB, peripheral blood; WBC, white blood cell.