Objective: To describe the MICM (morphology, immunology, cytogenetics and molecular biology) characteristics of a case of acute myelomonocytic leukemia M 4C . Methods: The medical history data of the case of M 4C admitted to our hospital was reviewed. The results of bone marrow cell morphology, cytochemical stains, bone marrow biopsy, immunophenotype, cytogenetics, molecular test and NGS (next-generation sequencing) of the case were analyzed. Results: The bone marrow smear showed markedly active proliferation of bone marrow cells in which the myelomonocytic cells accounted for 85.6%. Cytochemical stains showed peroxidase (POX) stain partially and weakly positive; specific esterase AS-DCE partially positive; non-specific esterase α-NBE partially positive and smothered by sodium fluoride; non-specific esterase AS-DAE partially positive and smothered by sodium fluoride. Bone marrow biopsy showed hyperproliferative cells and diffused hyperplasia of blasts. Immunophenotype analysis showed that the abnormal cell population was positive for CD11B, CD64, CD56, cMPO, CD33, CD41, CD61, CD38 and CD58, but negative for CD13, CD34, CD117, CD7, CD123, HLA-DR, CD10, CD19, CD20, CD2, CD14, CD235, CD15, CD303, CD304, CD25, cCD79a, cCD3, cCD22, CD1a and TDT. Cytogenetic analysis showed 47, XY, t(9;11) (p22;q23),+mar. The molecular test for leukemia showed MLLT3/KMT2A gene rearrangement. NGS showed NRAS and TET2 mutation. The case was finally diagnosed as AML (acute myelomonocytic leukemia) M 4C with t(9;11)(p22;q23), MLLT3-KMT2A. Conclusion Leukemia M 4C may show the characteristics of both granulocytes and monocytes with complex morphological features. The combined examination of MICM should be necessary for the diagnosis of M 4C with great significance.