The International Prognostic Scoring System (IPSS) for Myelodysplastic Syndromes was developed by Greenberg and colleagues in 1997 from a pooled analysis of 816 MDS patients from seven clinical trials. It uses three variables — cytogenetics, bone marrow blast percentage, and number of cytopenias — to stratify patients into four risk groups (Low, Intermediate-1, Intermediate-2, High) with dramatically different survival and AML transformation rates. The IPSS was revised in 2012 (IPSS-R) with improved cytogenetic risk grouping and continuous scoring to provide better prognostic discrimination, particularly in the lower-risk groups. MDS is a clonal stem cell disorder with annual incidence of ~4 per 100,000, predominantly affecting elderly patients.