Int J Lab Hematol. 2020;00:1–8. wileyonlinelibrary.com/journal/ijlh | 1 © 2020 John Wiley & Sons Ltd 1 | INTRODUCTION Acute myeloid leukemia (AML) with mutated nucleophosmin 1 (NPM1) accounts for approximately one-third of all AML cases. NPM1 is a nucleocytoplasmic shuttling protein that negatively af- fects the growth of the mutated cells and offers a good prognosis in AML. It is commonly associated with high total leukocytic count (TLC), acute myelomonocytic and acute monocytic leukemia, and CD34 negativity. 1 Although AML with mutated NPM1 is usually as- sociated with a normal karyotype, 40% of cases have co-occurring FMS-like tyrosine kinase internal tandem duplication (FLT3-ITD) mutations. 2,3 Nucleophosmin mutations were confirmed to confer a favorable prognostic impact on AML, though various reports were presented as how the presence of other mutations, for example, FLT3-ITD, DNMT3A, and IDH1/2 mutations, may negatively affect the good prognosis of NPM1 mutations. 4-8 Hence, "AML with mu- tated NPM1" has been included as a provisional entity in the WHO classification of tumors of hematopoietic and lymphoid tissues. 1 About 50 variants of NPM1 mutations have been identified in AML. Almost all these mutations are in exon 12, in a mutational hot Received: 6 May 2020 | Revised: 18 July 2020 | Accepted: 29 July 2020 DOI: 10.1111/ijlh.13317 ORIGINAL ARTICLE Flow cytometry in detection of Nucleophosmin 1 mutation in acute myeloid leukemia patients: A reproducible tertiary hospital experience Rasha Abd El-Rahman El-Gamal | Azza El-Sayed Hashem | Deena Mohamed Habashy | Menna Allah Zakareya Abou Elwafa | Noha Hussein Boshnak Department of Clinical Pathology, Hematology Unit, Ain Shams University, Cairo, Egypt Correspondence Rasha Abd El-Rahman El-Gamal, Clinical Pathology Department, Faculty of Medicine, Ain Shams University, Abbasseya, Cairo, 11566, Egypt. Email: rashaelgamal@hotmail.com Funding information Faculty of medicine Grants office, Grant/ Award Number: 2017/22 Abstract Introduction: Nucleophosmin 1 (NPM1) mutation is one of the most frequent gene mutations in adult acute myeloid leukemia (AML), being detected in 35% of all cases and in up to 60% of patients with normal karyotype AML. AML with mutated NPM1 has distinct pathology, immunophenotyping, and confirmed favorable prognostic sig- nificance. Hence, AML with mutated NPM1 is a separate entity in the revised 2016 World Health Organization classification. This study aimed to evaluate the use of a reproducible flow cytometry approach in the assay of mutant NPM1 protein in AML patients and to correlate flow cytometric results with the NPM1 gene mutation. Methods: Eighty-nine newly diagnosed AML patients were evaluated for the expres- sion of mutant NPM1 using flow cytometry and for the presence of NPM1 exon 12 mutations using high-resolution melting polymerase chain reaction (HRM PCR). Results: The NPM1 mutation was found in 35 (39.3%) patients by HRM PCR. These patients showed a significantly higher level of percentage of positive-stained cells (% positive cells) and normalized median fluorescence intensity (MFI) for mutant NPM1 by flow cytometry than the negative mutation group. Conclusion: Flow cytometric detection of mutant NPM1 offers a possible tool to indicate NPM1 mutational status. KEYWORDS acute myeloid leukemia, flow cytometry, HRM PCR, NPM1