Clinical significance of phenotypic features of blasts in patients with myelodysplastic syndromes

Knowledge of the blast phenotype in myelodysplastic syndromes (MDS) would be valuable, as in other malignancies, but remains sparse. This is mainly because MDS blasts are a minor population in clinical samples, making analysis difficult. Thus, for this blast phenotype study, we prepared blast-rich specimens (using a new density-centrifugation reagent for harvesting blasts) from blood and marrow samples of 95 patients with various MDS subtypes and 21 patients with acute leukemia transformed from MDS (AL-MDS). Flow cytometry revealed that a high proportion of the enriched blast cells (EBCs) from almost all cases showed an immunophenotype of committed myeloid precursors (CD34CD38HLA-DRCD13CD33), regardless of the disease subtype. The cytochemical reaction for myeloperoxidase was negative in 58% of the cases. Thus, the EBC phenotype is more immature in MDS than in de novo acute myeloid leukemia. MDS EBCs often coexpressed stem-cell antigens and late-stage myeloid antigens asynchronously, but rarely expressed Tand B-lymphoid cell-specific antigens. Markers for myeloid-cell maturation (CD10 and CD15) were more prevalent on EBCs from low-risk MDS (refractory anemia [RA] and RA with ringed sideroblasts), while markers for myeloid-cell immaturity (CD7 and CD117) were more prevalent on EBCs from high-risk MDS (chronic myelomonocytic leukemia, RA with excess blasts [RAEB] and RAEB in transformation) and AL-MDS. A shift to a more immature phenotype of EBCs, accompanying disease progression, was also documented by sequential phenotyping of the same patients. Further, CD7-positivity of EBCs was an independent variable for a poor prognosis in MDS. These data represent new, valuable information regarding MDS. Corresponding author's e-mail: [email protected] For personal use only. on October 31, 2017. by guest www.bloodjournal.org From