Advances in the diagnosis and classification of myelodysplastic syndromes

The diagnosis and classification of myelodysplastic syndromes (MDS) present unique challenges, particularly in the distinction from benign conditions that can cause cytopenia. The diagnostician must effectively incorporate information from several morphologic modalities (trephine biopsy, aspirate smear, and peripheral blood smear) as well as a myriad of ancillary testing results, such as flow cytometry, cytogenetics, and, increasingly, molecular genetic testing results. Our understanding of the pathogenesis of MDS has evolved rapidly in recent years, largely due to advances in molecular genetic technology and more complete characterization of genetic aberrations and gene expression patterns. The 2008 WHO Classification is currently being updated to incorporate this new information. In this review, the principles of bone marrow interpretation with respect to the diagnosis and classification of MDS in the current era will be reviewed, including accurate morphologic interpretation, use of flow cytometry and immunohistochemistry, appropriate use of cytogenetics, and the emerging role of molecular genetics.