Diagnosing myelodysplastic/myeloproliferative neoplasms: laboratory testing strategies to exclude other disorders.

INTRODUCTION: The 2008 World Health Organization classification of myeloid neoplasms includes the diagnostic category, myelodysplastic/myeloproliferative neoplasms (MDS/MPN), which encompasses those rare clonal myeloid proliferations that at initial presentation, show overlapping myeloproliferative and myelodysplastic features, making classification as either a myelodysplastic syndrome (MDS) or myeloproliferative neoplasm (MPN) problematic. There are four main subcategories, chronic myelomonocytic leukemia (CMML), atypical chronic myeloid leukemia, BCR-ABL1-negative (aCML), juvenile myelomonocytic leukemia (JMML), and myelodysplastic/myeloproliferative neoplasm, unclassifiable (MDS/MPN-U), which also includes the provisional entity, refractory anemia with ring sideroblasts associated with marked thrombocytosis (RARS-T). Notably, the morphological features typical of MDS/MPNs are not specific and can be seen in other myeloid neoplasms at presentation or as part of disease progression or transformation.

METHODS AND RESULTS: This review presents a laboratory approach to diagnosing MDS/MPNs in adults that allows for the exclusion of other disorders that may be otherwise indistinguishable. Ancillary studies including cytochemistry, immunohistochemistry, flow cytometry, and genetic testing are discussed.

CONCLUSION: The most appropriate classification of myeloid neoplasms presenting with hybrid myelodysplastic/myeloproliferative features requires a comprehensive clinical and laboratory assessment with careful integration of the morphological, immunophenotypic, genetic, and clinical characteristics.