The utility of a myeloid mutation panel for the diagnosis of myelodysplastic syndrome and myelodysplastic/myeloproliferative neoplasm

Introduction: The diagnosis of myelodysplastic syndromes (MDS) and myelodysplastic/myeloproliferative neoplasms (MDS/MPN) is based on morphology and cytogenetics/FISH findings per 2017 WHO classification. With rare exceptions, somatic mutations have not been incorporated as the diagnostic criteria. Methods: We analyzed the utility of mutational analysis with a targeted 54-gene or 40-gene next-generation sequencing (NGS) panel in the diagnosis of MDS and MDS/MPN. Results: We retrospectively collected 92 patients who presented with unexplained cytopenia with or without cytosis, including 32 low-grade MDS (MDS-L), 18 high-grade MDS (MDS-H), 5 therapy-related MDS (MDS-TR), 19 MDS/MPN, and 18 negative cases. Of 92 patients, 197 somatic mutations involving 38 genes were detected and had variant allele frequency (VAF) ranging from 3% to 99%. The most common mutated genes were TET2, ASXL1, RUNX1, TP53, SRSF2, and SF3B1. MDS-L, MDS-H, MDS-TR, and MDS/MPN showed an average number of somatic mutations with a mean VAF of 1.9/33%, 2.6/30%, 2/36%, and 4/41%, respectively. SF3B1 mutations were exclusively observed in MDS-L and MDS/MPN. TP53 gene mutations were more frequently seen in MDS-H and MDS-TR. Among 34 patients with a diagnosis of MDS or MDS/MPN with normal cytogenetics, 31 patients (91%) had at least 1 mutation and 24 patients (71%) had ≥2 mutations with ≥10% VAF. Conclusion: A myeloid mutational panel provides additional evidence of clonality besides cytogenetics/FISH studies in the diagnosis of cytopenia with or without cytosis. Two or more mutations with ≥10% VAF highly predicts MDS and MDS/MPN with a positive predictive value of 100%.