[FLT3-ITD and NPM1 mutation positive acute myeloid leukemia with cuplike blasts mimicking acute promyelocytic leukemia].

FMS-like tyrosine kinase 3 (FLT3) inhibitors improve the prognosis of FLT3-internal tandem duplication (ITD)-positive acute myeloid leukemia (AML). Case 1 is a 47-year-old male patient who presented with a white blood cell count (WBC) of 95,700/ml with 94% blast accompanied by cuplike nuclei, lactate dehydrogenase (LDH) of 2,434 IU/l, fibrin degradation products (FDP) of 476 mg/ml, and a bone marrow examination that revealed blastic marrow with chromosome 46, XY, positive FLT3-ITD, and positive nucleophosmin 1 (NPM1) mutation type A. Flow cytometry revealed that blasts were positive for CD33 and negative for CD34, CD117, and human leukocyte antigen-DR isotype (HLA-DR). The patient had no response to idarubicin combined cytarabine; however, qiuzartinib administration resulted in the first complete remission. Case 2 is a 71-year-old female patient, who presented with 94,900/ml of WBC with a 91% blast accompanied with cup-like nuclei, LDH of 19,03 IU/l, FDP of 112 mg/ml, and a peripheral blood examination that revealed chromosome 46, XX, positive FLT3-ITD, and positive NPM1 mutation type B. Flow cytometry revealed that blasts were positive for CD33 and negative for CD34, CD117, and HLA-DR. She had a partial response to venetoclax combined with azacytidine, and qiuzartinib administration resulted in the first complete remission. Both cases were CD34- and HLA-DR-negative with disseminated intravascular coagulation mimicking acute promyelocytic leukemia (APL). Additionally, recognizing the cuplike blasts is useful to differentiate FLT3 mutant AML from APL for the proper use of FLT3 inhibitors.