Altered Immunophenotypes on Leukemic and/or Monocytic Cells from Acute Myeloid Leukemia Highly Predict for Nucleophosmin Gene Mutation

Introduction. Nucleophosmin gene mutation (NPM1mut) occurs in around 30% of acute myeloid leukemia (AML) patients, frequently linked with favourable prognosis in the absence of FLT3-ITDmut, which occurs in around 40% of NPM1mut AML. Therefore, more expeditious diagnostic approaches may contribute to early diagnosis and prognostic stratification of these patients. Herein, we investigated the association of immunophenotypic features of leukemic and monocytic cells with the presence of NPM1mut in AML. Methods. A total of 404 bone marrow (BM) samples from newly-diagnosed AML patients according to WHO 2017 classification were retrospectively studied by 8-color flow cytometry, including 225 AML with NPM1mut and 179 cases wild type gene (NPM1wt). Information on FLT3-ITD could be obtained from 397/404 cases. Thus, FLT3-ITDmut was present in 85/397 (21%), being concomitant with NPM1mut in 62/85 AML cases (73%). Logistic regression analysis was used to identify predictive phenotypes for the presence of NPM1mut. Results. Overall, blast cell with immunophenotypic features of monocytic differentiation (corresponding to FAB M4 and M5 AML subtypes) were observed among 135/225 (60%) and 69/179 (38.5%) AML patients with NPM1mut and NPM1wt, respectively (p Among AML with monocytic blast cell differentiation, altered monocytic phenotypes were more frequent among NPM1mut vs. NPM1wt cases (98% vs. 36%) (p Noteworthy, in AML cases without blast cell monocytic differentiation, remaining monocytic cells showed similar asynchronous phenotypic patterns, which were also more frequent among NPM1mut cases (78% vs. 23% of NPM1wt cases, respectively; p In addition, aberrant CD9 blast cell expression was found in a significant proportion of all AML cases studied (124/222, 56%). However, altered CD9 was more frequent on (either monocytic or immature/myeloid) blast cells from AML cases with NPM1mut (76% vs. 46% NPM1wt cases; p 0.05). In turn, aberrant CD25 expression on blast cells was otherwise linked to FLT3-ITDmut (61% vs. 20% of FLT3-ITDwt cases; p In multivariate analysis, baseline detection of monocytic-lineage blast cells with asynchronous expression of CD300 prior CD14 -C-index= 0.954, odds ratio (OR), 78.8; 95% confidence interval (CI), 13.1-471; p Conclusions. Detection of specific aberrant immunophenotypic patterns among blast cells and/or remaining monocytic cells from AML patients is highly predictive for NPM1mut, which may contribute to early diagnosis and follow-up of these patients. Disclosures Diez-Campelo: Celgene Corporation: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding.