In order to confirm the diagnosis of BPDCN, the following immunophenotypic diagnostic criteria have to be met: expression of CD123 and one other plasmacytoid dendritic cell marker in addition to CD4 and/or CD56 or expression of any three plasmacytoid dendritic cell markers and absent expression of all expected negative markers [9,14]. Morphologically, the cells are blast-like and medium-sized. The gene discussed is NCAM1; the disease is CD4+/CD56+ hematodermic neoplasm.