Morphologic, immunophenotypic, and molecular genetic comparison study in patients with clonal cytopenia of undetermined significance, myelodysplastic syndrome, and acute myeloid leukemia with myelodysplasia-related changes: A single institution experience.

INTRODUCTION

Next-generation sequencing (NGS) analysis showed clonal cytopenia of undetermined significance (CCUS) as an immediate precursor to myelodysplastic syndrome (MDS).

METHODS

We evaluated and compared morphologic, multiparametric flow cytometry (MFC), and molecular genetic findings in patients with CCUS (n = 37), MDS (n = 75), and acute myeloid leukemia with myelodysplasia-related changes (AML-MRC, n = 24).

RESULTS

CCUS patients showed variable MFC abnormalities including >2% CD34+ myeloblasts (5.8%), altered antigen expression on myeloblasts, monocytes, and granulocytes (1.2, 1.5, and 0.2/case), abnormal maturation of myeloblasts (45.8%), decreased hematogones (17.6%), and decreased side scatter (SSC) of granulocytes (11.4%). CCUS patients with high-risk mutations showed significantly more MFC abnormalities. However, CCUS patients with >20% variant allelic fraction (VAF) did not show more MFC aberrations than the rest of the group. MDS patients showed significantly more MFC abnormalities compared with CCUS patients (p = 7.8E-05-0.047). Low-grade MDS patients showed significantly fewer MFC abnormalities compared with high-grade MDS or AML-MRC patients (p = 1.89E-05-0.04). AML-MRC patients showed significantly elevated blast counts, more antigen aberrations, decreased hematogones, and decreased SSC of granulocytes compared with CCUS patients (p = 2.0E-05-0.01). CCUS patients carried predominantly TET2/DNMT3A/ASXL1 mutations. They harbored fewer mutations in gene coding splicing factors compared with MDS patients (p = .0001-.02) and fewer mutations in tumor suppressor and transcription factor genes compared with AML-MRC patients (p = .0006-.02).

CONCLUSIONS

CCUS is an immediate precursor to low-grade MDS. The progression from CCUS to MDS to AML-MRC is a stepwise process that requires acquisition of mutations in splicing, transcription factor, and tumor suppressor genes with accumulations of additional MFC abnormalities.