Decoding MDS/MPN: How to Navigate the Complex World of Myeloid Neoplasms
"A comprehensive guide to understanding the challenges, classifications, and management of myelodysplastic/myeloproliferative neoplasms."
The landscape of chronic myeloid neoplasms spans a spectrum of conditions, from myelodysplastic syndromes (MDS), marked by ineffective hematopoiesis, to myeloproliferative neoplasms (MPN), characterized by proliferative features. Bridging these categories is a group of diseases recognized as MDS/MPN, sharing clinical, pathological, and molecular characteristics. In 2008, the World Health Organization (WHO) formally recognized this overlap, defining specific entities within this category.
Over the past decade, significant strides have been made in understanding MDS/MPN. Researchers have refined diagnostic criteria, developed risk-stratification models, and explored the underlying biology of these conditions. Treatment strategies have been adapted from those used for MDS and MPN, with ongoing efforts to define the clinical benefits of specific therapies for this unique group of patients.
This guide aims to illuminate recent efforts to better understand MDS/MPN, explore the diagnostic and management challenges, and define the areas where further progress is needed.
Global Burden and Trends
MDS and MPN are clonal bone-marrow disorders associated with ineffective hematopoiesis, abnormal cellular proliferation, and a risk of transformation into acute myeloid leukemia. A global, regional, and national analysis examined burden trends and cross-country inequalities over the past 30 years and forecast potential changes through 2045. The American Cancer Society reports that new MDS diagnoses in the United States are likely increasing as the population ages.
Diagnostic Complexity
A practical diagnostic pathway may begin with complete blood count findings, followed by peripheral blood smear review and additional evaluation leading to a final diagnosis. Contemporary WHO classification updates have revised multiple entities within the MPN and MDS/MPN categories, reflecting the complexity of distinguishing related myeloid neoplasms. The growing diagnostic complexity means that classification systems and pathology workflows remain essential but require continual updating.
From Clonality to Evolution
MDS is described as a clonal myeloid malignancy characterized by cytopenia, bone-marrow dysplasia, and variable risk of progression to acute myeloid leukemia. The introduction of hypomethylating agents about 20 years ago represents a major therapeutic milestone, although later advances have remained limited. Research on MPN, MDS, and related conditions has increasingly supported large-scale sequencing combined with clinical and laboratory data to create more biologically grounded classifications.
Unraveling the Diagnostic Challenges and Classification Updates in MDS/MPN
MDS/MPN are defined by features of both MDS and MPN, making the diagnosis a challenge. The WHO diagnostic criteria are summarized in Table 1. The revised WHO 2016 classification retained the original MDS/MPN subtypes with further refinement and nomenclature (Table 1). For CMML, persistent monocytosis more than 3 months is adequate for diagnosis, even with a lack of morphologic dysplasia. The challenge is excluding other causes of monocytosis, cytogenetic abnormalities, and somatic mutations, which may help identifying clonal hematopoiesis, ruling out the reactive process. The coexistence of TET-2 and SRSF2 somatic mutations are suggested to be highly specific for CMML.
- CMML (Chronic Myelomonocytic Leukemia): Diagnosed by persistent monocytosis (over 3 months). Subtypes (CMML-0, CMML-1, CMML-2) are classified based on blast percentages in the blood and bone marrow. Crucially, other causes of monocytosis must be ruled out, including infections and inflammatory conditions. Genetic markers can help confirm clonality.
- aCML (Atypical Chronic Myeloid Leukemia): Diagnosed as BCR/ABL1 negative. Requires exclusion of CML and presence of granulocytic dysplasia.
- RARS-T (Refractory Anemia with Ring Sideroblasts and Thrombocytosis): Now known as MDS/MPN-RS-T. Diagnosis requires a high platelet count and ring sideroblasts in the bone marrow. Common mutations include SF3B1, JAK2 and CALR.
- JMML (Juvenile Myelomonocytic Leukemia): Typically diagnosed in children with persistent monocytosis, absence of BCR-ABL or PDGFR fusion genes, and specific genetic abnormalities.
- MDS/MPN-U (Unclassifiable): Diagnosed when features of both MDS and MPN are present, but the condition doesn't fit into other defined categories. Requires careful exclusion of other possibilities.
An Evolving Evidence Base
Recent work continues to examine MDS and MDS/MPN as biologically diverse disorders rather than a single uniform disease. Current research is likely to refine understanding of disease biology, classification, and treatment, but the available evidence should be interpreted carefully because findings and clinical applications may continue to change. In the absence of a specific source set for this subsection, no particular study, therapy, or numerical result is asserted here.
Persistent Clinical Challenges
MDS comprises diverse malignancies that can produce ineffective hematopoiesis, cytopenias, bone-marrow failure, and variable risk of progression to acute myeloid leukemia. Reviews describe substantial progress over the past two decades in understanding genetic mutations and immune contributions, yet these advances have not eliminated the biological and clinical heterogeneity of the disease. Refined molecular knowledge and classification systems therefore coexist with continuing challenges in achieving consistently effective management.
Comparing Complex Disorders
Comparative analysis of MDS/MPN disorders requires attention to both shared and differing biological and clinical features. Because no specific comparative sources were provided for this subsection, conclusions about relative prognosis, diagnostic performance, or treatment effectiveness would be premature. The most defensible comparison is therefore one that acknowledges heterogeneity rather than treating all myeloid neoplasms as interchangeable.
Future Directions and the ABNL MARRO Study
The MDS/MPN International Working Group is actively working to advance therapies for MDS/MPN. Soon, they will begin the ABNL MARRO (A Novel therapy combinations in untreated MDS/MPN And Relapsed/Refractory Overlap Syndromes) basket trial. This trial will incorporate novel therapies with a DNA methyltransferase inhibition backbone for patients with previously treated or treatment-naïve MDS/MPN.
Integrating the Evidence
A balanced synthesis of MDS/MPN research must connect disease biology, diagnostic classification, clinical heterogeneity, and patient experience. Without a dedicated source set for this subsection, specific expert judgments or treatment recommendations cannot be attributed here. The evidence supplied across the broader topic supports a cautious interpretation in which progress is real but incomplete.
The Road Ahead
Future progress will likely depend on improving how clinicians classify biologically diverse myeloid neoplasms and translate molecular understanding into useful care. The direction of research may include better integration of clinical, laboratory, and molecular information, but no specific future intervention or forecast is supported by sources assigned to this subsection. Expectations should therefore remain appropriately measured.
Rarity and Diagnostic Burden
MDS/MPN overlap syndromes are described as a unique and challenging group of hematological disorders whose biology and genetic abnormalities are increasingly understood. Their rarity creates diagnostic challenges even for experienced hematopathologists, while their overlap of dysplastic and proliferative features complicates classification. Current therapeutic landscapes include treatments directed at specific pathways in malignant myeloid cells, but biological complexity remains a central systemic challenge.
Burden Beyond the Diagnosis
MDS is associated with bone-marrow failure, peripheral-blood cytopenias, and a risk of progression to acute myeloid leukemia, which can carry a poor prognosis and low survival rates. A 2024 real-world study combined patient surveys with chart reviews to document clinical practice and the burden of MDS, including physicians' perspectives. Real-world evidence therefore adds patient and care-delivery context to laboratory and classification findings.