Presence of peripheral blasts in refractory anemia and refractory cytopenia with multilineage dysplasia predicts an unfavourable outcome

The World Health Organization (WHO) assigns myelodysplastic syndrome (MDS) to RA/RCMD/RARS/RSCM/5q− syndrome, if medullary blasts are <5% and peripheral blast (PB) count ≤1%. In 1103 patients with these diagnoses, we analysed survival and risk of AML evolution depending on the presence of PB. Median survival in the group with 1% PB (n = 74) was significantly lower as compared to those without PB (20 versus 47 months, p < 0.00005). Cumulative risk of AML was significantly higher in patients showing PB (p < 0.00005). Median survival of patients with PB was not different from that of RAEB I. We therefore propose to consider patients with PB, regardless of medullary blast, as RAEB I.