This case demonstrates the clinical significance of the immature white blood cell (WBC) differential parameters (IMG, IMM, IML) of the Yumizen hematology analyzer series. In this case, IMM and LIC were particularly useful. These parameters assisted the laboratory physician in making a provisional diagnosis of Acute Myeloid Leukemia and, with the help of IMM, identifying monocytic lineage. The immature WBC differential parameters on the Yumizen hematology analyzers can aid the laboratory in classigying various WBC-related pathologies, enabling specific diagnostic approaches and clinical management.