Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare disease characterized by malignant proliferation of blastic plasmacytoid dendritic cells, which are generally found positive for CD4, CD56, as well as antigens associated with plasmacytoid dendritic cells (pDCs), such as CD123, TCL1, BDCA2, and BDCA4.1 The gene discussed is CD4; the disease is CD4+/CD56+ hematodermic neoplasm.