<i>ZMYND11::MBTD1</i> Fusion in Myeloid/NK Cell Precursor Leukemia: A Case Report With Literature Review and Diagnostic Implications

Myeloid/NK cell precursor leukemia (MNKPL) is a rare, aggressive entity often misdiagnosed as acute myeloid leukemia (AML) or aggressive NK cell leukemia (ANKL) because of overlapping markers (CD7⁺, CD13/CD33⁺, CD56⁺, myeloperoxidase [MPO]-). We report a patient initially diagnosed with ANKL; subsequent flow-cytometric reevaluation (CD7⁺, CD13⁺, CD33⁺, CD34⁺, CD56⁺, CD117⁺, MPO^-) supported a diagnosis of MNKPL. RNA sequencing and nested PCR identified an in-frame ZMYND11::MBTD1 fusion. A review of published ZMYND11::MBTD1 leukemias (n = 5) found immunophenotypes highly consistent with MNKPL, suggesting prior misclassification. These findings support ZMYND11::MBTD1 as a recurrent lesion in MNKPL and a practical aid to diagnosis and treatment selection.