Overview of Myelodysplastic/Myeloproliferative Neoplasms
Kathryn Foucar, MD
 Blood smear from a patient with MDS/MPN shows marked leukocytosis with left shift. The patient also has a moderate anemia, while the platelet count is preserved. Note dysplastic neutrophils  . |
 Marked dysplastic features of neutrophils are evident in this peripheral blood smear from a patient with MDS/MPN. Note the nuclear segmentation abnormalities and hypogranularity of the neutrophil  . |
TERMINOLOGY
Abbreviations
Myelodysplastic/myeloproliferative neoplasms (MDS/MPN)
Definitions
De novo clonal chronic myeloid neoplasm characterized by hybrid myelodysplastic and myeloproliferative features manifested by at least 1 cytopenia and at least 1 cytosis in blood
Maturation is intact, mature cells predominate
Blasts and blast equivalents are < 20% in blood and bone marrow
Multiple subtypes defined with specific criteria
WHO 2008 Classification of MDS/MPN
Chronic myelomonocytic leukemia (CMML)
Atypical chronic myeloid leukemia, BCR-ABL1 negative (aCML)
Juvenile myelomonocytic leukemia (JMML)
Myelodysplastic/myeloproliferative neoplasm, unclassifiable (MDS/MPN-U)
Refractory anemia with ring sideroblasts and thrombocytosis (RARS-T) (provisional category)
ETIOLOGY/PATHOGENESIS
Molecular Genetic Findings
No disease defining molecular/cytogenetic features
Aberrations in RAS/MAPK signaling pathways common and linked to abnormal cell proliferation
May include mutations in PTNPN11, NRAS, KRAS, or NF1 most notably in JMML
Many exclusionary genetic findings including absence of BCR-ABL1, PDGFRA/B, FGFR1 mutations, isolated del(5q), inv3(q21q26), and AML-defining translocations
All of these mutations are pathogenetically linked to other types of myeloid neoplasms
EPIDEMIOLOGY
