Preleukemic myelodysplastic syndromes (MDS): pathogenetical considerations based on retrospective...

Area of Science:

• Hematology
• Oncology
• Stem Cell Biology

Background:

• Myelodysplastic syndromes (MDS) are a group of clonal hematopoietic stem cell disorders.
• MDS often transform into acute myeloid leukemia (AML).
• The sequential progression and underlying mechanisms of MDS transformation remain incompletely understood.

Purpose of the Study:

• To analyze the sequential morphological changes in myelodysplastic syndromes (MDS) preceding overt leukemia.
• To investigate the relationship between MDS phases and the subsequent development of leukemia.
• To explore the cellular mechanisms underlying the transition from MDS to leukemia.

Main Methods:

• Retrospective analysis of bone marrow morphology in 77 patients with MDS progressing to overt leukemia.
• Classification of MDS into distinct phases based on cellularity and lineage involvement.
• Evaluation of the pattern of leukemic transformation (local vs. diffuse) and cellular characteristics.

Main Results:

• Three non-reversible phases of MDS were identified: hypocellular dysplasia (H), hypercellular erythropoiesis-predominant (E), and myelo(mono)poiesis-predominant (MM).
• Leukemic transformation occurred locally in some cases, with mature myeloid cells exhibiting leukemic infiltration capacity.
• A correlation was observed between the MDS phase and leukemia differentiation, suggesting varying risks for stem cell subpopulations.

Conclusions:

• MDS represents a spectrum of disease phases rather than distinct entities.
• Leukemia development in MDS likely results from multiple initiating events, leading to leukemic subclones within the MDS clone.
• The phase of MDS influences the susceptibility of specific stem cell subpopulations to leukemogenic events.