Objectives: Myelodysplastic syndromes (MDS) are a group of myeloid neoplasms that are often difficult to diagnose due to their pathologic and clinical heterogeneity. The key features of MDS are peripheral blood cytopenias, ineffective hematopoiesis manifesting as morphologic dysplasia, and clonal genetic abnormalities. The most difficult diagnostic dilemmas often arise in low-grade MDS cases (lacking excess blasts), which can be difficult to distinguish from other causes of cytopenia. This distinction requires the integration of information from the peripheral blood (both CBC parameters and morphology), bone marrow morphology, genetic studies, and interrogation of the clinical record to exclude secondary causes.
Methods: We discuss the approach to the diagnosis of low-grade MDS (cases lacking increased blasts), including a diagnostic algorithm and two illustrative cases.
Results: The appropriate use of ancillary studies is important to support or dispute the likelihood of low-grade MDS in conjunction with the findings of morphologic dysplasia. Interpreting the results of cytogenetics and next-generation sequencing can be challenging and must incorporate the emerging knowledge of clonal hematopoiesis of indeterminate potential.
Conclusions: The role of pathologists in integrating data from multiple sources in the diagnosis of low-grade MDS is evolving and becoming increasingly complex; in this challenging diagnostic setting, it is important to feel comfortable with uncertainty and maintain a conservative approach.