Table 3 Comparison of WHO-HAEM5 and ICC classification of adult MDS

SF3B1 mutation

MDS with low blasts and SF3B1 mutation

MDS with mutated SF3B1

• ICC requires SF3B1 VAF of ≥10%, WHO requires VAF of ≥5%

• ICC excludes cases with abnormal 3q26.2 and RUNX1 mutation

TP53 mutation

MDS with biallelic TP53 inactivation

MDS with mutated TP53

• ICC requires TP53 VAF of ≥10%, WHO has no minimal VAF

• ICC allows mono-allelic TP53 mutation for cases with 10–19% blasts (MDS/AML), WHO requires bi-allelic mutation for all cases

• ICC, but not WHO allows complex karyotype to qualify for bi-allelic mutation if TP53 LOH status is unknown

Del(5q)

MDS with isolated deletion (5q)

MDS with del(5q)

• WHO, not ICC, requires dysplasia in at least 10% of cells in at least 1 lineage

Blast excess or Auer rods

MDS with increased blasts-1 (MDS-IB1)

MDS with increased blasts-2 (MDS-IB2)

MDS with increased blasts and fibrosis (MDS-F)

MDS with excess blasts (MDS-EB)

MDS/AML

WHO IB2 mostly equivalent to MDS/AML and WHO IB1 mostly equivalent to MDS-EB. However:

• Cases with Auer rods and < 10% blasts are MDS-EB in ICC and MDS-IB2 in WHO

• Cases with 5–9% PB blasts are MDS-EB in ICC and MDS-IB2 in WHO

• WHO MDS-F corresponds to ICC MDS-EB and MDS/AML cases with grade 2–3 fibrosis

No blast excess

MDS with low blasts

MDS, hypoplastic

MDS with low blasts and ring sideroblasts

MDS-NOS-SLD

MDS-NOS-MLD

WHO subdivides these cases based on marrow hypocellularity or ≥15% ring sideroblasts; ICC subdivides these cases based on dysplasia in 1 versus 2–3 hematopoietic lineages.