Myelodysplastic Syndrome with Excess Blasts 2 (MDS-EB-2): A Historical Overview and Review of Forthcoming Classifications.

OBJECTIVES:Myelodysplastic syndrome with excess blasts-2 (MDS-EB-2) primarily affects adults older than 50 years and confers a worse prognosis with a higher risk of transformation to acute myeloid leukemia (AML) compared to myelodysplastic syndrome (MDS) and MDS with excess blasts-1 (MDS-EB-1). In ordering diagnostic studies for MDS, cytogenetic and genomic studies are vital as they have significant clinical and prognostic implications for the patient. We present a case of a 71-year-old male diagnosed with MDS-EB-2 with a pathogenic loss-of-function TP53 variant and discuss presentation, pathogenesis, and the importance of thorough diagnostic testing through multiple modalities to accurately diagnose and subtype MDS. In addition, we explore a historical overview of the diagnostic criteria of MDS-EB-2 and how it has changed over time from the World Health Organization (WHO) 4th edition in 2008, the WHO revised 4th edition in 2017, and the upcoming WHO 5th edition and International Consensus Classification (ICC) for 2022.