NCAM1 and CD4+/CD56+ hematodermic neoplasm: BPDCN was previously classified as blastic NK-cell lymphoma or CD4+CD56+hematodermic neoplasm because of the expression of the NK cell marker, CD56; however, subsequent phenotypic (e.g. BDCA-2, IL3-Ra/CD123) and molecular studies identified plasmacytoid dendritic cells (pDCs) as a normal cellular counterpart of BPDCN3.