NPM1 exon 5 mutations in acute myeloid leukemia: Implications in diagnosis and minimal residual monitoring

[...]the vast majority of amplicon-based assays currently used in clinical laboratories are designed to target the mutational hotspots in exon 12. [...]line of therapy was on protocol [ 8] with azacitidine, cytarabine, and mitoxantrone with residual disease followed by a hematopoietic stem and progenitor cell transplant before relapsing. (E, F) Immunostaining performed with NPM1 antibody (Dako clone 376, pan NPM1) confirmed aberrant cytoplasmic as well as retained nucleolar staining (inset images) (total magnification 1000×) Overall, we confirm that NPM1 exon 5 in-frame insertions or duplications are an uncommon but recurrent finding in AML. Because AML with mutated NPM1 has been recognized as a distinct entity based on a single gene mutation by the WHO classification of AML [ 1], identification of NPM1 mutations is critical for accurate AML diagnosis and patient management [ 10].