Validation and proposals for a refinement of the WHO 2008 classification of myelodysplastic syndromes without excess of blasts.

In 2008, the WHO proposed changes in the classification of MDS regarding RCUD and MDS unclassifiable. We validated these proposals by using 2032 patients of the Düsseldorf MDS Registry. 10% of the patients had RCUD and 6% MDS-U. Among patients with RCUD, only 9% had RN and 6% had RT. There was no correlation between dysplastic cell line and type of cytopenia. There was no difference in prognosis between RCMD and MDS-U and between RA, RT, and RN. The separation of RA, RN, and RT is not justified suggesting a consolidation as RCUD. MDS-U should be integrated into RCMD.