Abstract: Objective To report a case of blastic plasmacytoid dendritic cell neoplasm（BPDCN）,and to detail the characteristics of its clinical manifestation,cell morphology,immunophenotype and karyotype analysis,which may show new light on the diagnosis of the disease. Methods The case was diagnosed by its clinical manifestation,cell morphology and immunophenotype. Literature review was performed to reveal the clinical characteristics of BPDCN. Results The results of bone marrow smear demonstrated the presence of a dramatically active myeloid hyperplasia,and the presence of the blast cell was 37.5%,with the characteristic of median size,circular or elliptic or irregular nucleus,loose chromatin,0 to 3 nucleolus,dispersed gray-blue cytoplasm and vacuolation which was often observed at the edge of cytoplasm. Peroxidase（POX）staining showed the blast cells were negative,while periodic acid-schiff（PAS） staining displayed that they were positive. Flow cytometric analysis of the bone marrow revealed the presence of the abnormal cells was 13.15%,and they were strongly positive for HLA-DR,CD56,CD123,positive for CD33,CD7,CD4,partially positive for CD38,and negative for cCD3,cCD22,cMPO,CD3,CD10,CD34,CD117. The result of karyotype analysis was 46,XY（20）. The patient was diagnosed as BPDCN with the clinical manifestation,cell morphology and immunophenotype. Conclusions The characteristics of clinical manifestation,cell morphology and immunophenotype are of clinical significance to diagnose BPDCN,and the characteristics of immunophenotype is indispensable.

Key words: Blastic plasmacytoid dendritic cell neoplasm, Cell morphology, Immunophenotype