Be careful of the masquerades: differentiating secondary myelodysplasia from myelodysplastic syndromes in clinical practice

In patients suspected to have myelodysplastic syndrome (MDS), especially in those patients without cytogenetic abnormalities or blast excess, accurate morphologic review by an expert hematopathologist and meticulous exclusion of other secondary causes of myelodysplasia are vital to establish the diagnosis. Errors in diagnosis can lead to dangerous consequences such as the administration of hypomethylating agents, lenalidomide, or even the use of intensive chemotherapy or allogeneic hematopoietic cell transplantation in patients who do not have an underlying MDS or even a malignant hematopoietic process. Additionally, beyond the possible harm and lack of efficacy of such therapies if the diagnosis of MDS is erroneous, the secondary myelodysplasia and resultant cytopenias are not likely to resolve unless the underlying etiology is identified and addressed. Discriminating a malignant process such as MDS from non-malignant secondary myelodysplasia can be quite challenging, and community hematologists/oncologists should consider referral to specialized physicians (both clinical experts and experienced hematopathologists) if there is any doubt regarding the diagnosis. In this article, we present a representative case series of patients from our own practice who posed diagnostic dilemmas and propose a systematic approach for assessment for secondary causes of myelodysplasia.