Clinical features of FLT3 mutation-positive AML in our hospital

Abstract

[Background] FMS-like tyrosine kinase 3 (FLT3) mutations, which are positive in about 25% of acute myeloid leukemia (AML) patients, are known to be a poor prognostic factor associated with a high relapse rate. In this study, we investigated the clinical characteristics of AML patients with FLT3 mutation-positive AML. [Subjects and Methods] The subjects were 24 patients diagnosed with AML between 2022 and 2024. Blood test data, morphological characteristics of bone marrow smears, cell surface markers, and chromosome and genetic test results were examined. [Results] Seven of the 24 patients were positive for FLT3 mutation, and all of them had FLT3-ITD mutation. Three of the seven FLT3 mutation positive patients showed a marked increase in leukocyte counts, while two patients showed a decrease in leukocyte counts. In cell surface markers, CD34 was deleted in all cases and HLA-DR was down-regulated in three cases. In addition, CD123 and CD25 were both positive in two cases. Chromosomal and genetic examination revealed normal karyotype and negative leukemia chimerism screening except for a case with KMT2A mutation. Three cases of NPM1 mutation were also observed. [Conclusion] In the FLT3 mutation-positive group, there were cases with markedly increased leukocyte counts and negative or decreased expression of both CD34 and HLA-DR as cell surface markers, and positive CD123 and CD25. Furthermore, WT-1 mRNA tended to be higher in the mutation positive group than in the mutation-negative group. These findings suggest the possibility of FLT3 mutation positivity.