Myeloid neoplasms with elevated plasmacytoid dendritic cell differentiation reflect the maturation process of dendritic cells.

To date, the research on dendritic cells (DCs) and their correlated neoplasms has not been clear. Blastic plasmacytoid dendritic cell neoplasm (BPDCN) and mature plasmacytoid dendritic cell proliferation (MPDCP) are two types of malignancies originating from plasmacytoid dendritic cells (pDCs). Some evidence has indicated the existence of other pDC neoplasms. In addition, cases of myeloid neoplasms (MNs), acute myeloblastic leukemia (AML), and myelodysplastic syndrome (MDS) with increased pDCs (AML/MDS-pDCs) seem to have immature DCs according to the vaguely consistent expression of markers among MNs and pDCs, which appear to fit the developmental pattern of normal DCs. We analyzed 14 AML/MDS-pDC cases mainly for their immunophenotype by flow cytometry and inferred their CD expression pattern. The patients' clinical information and other laboratory data were collected and reviewed. AML/MDS-pDCs show a different pattern of markers from BPDCN and MPDCP. Three maturation-involved stages were found in these AML/MDS-pDCs patients. Stage I was the most immature stage and displayed an expression profile of CD34(+/st+) CD117(+/st+) BDCA2(-) BDCA4(-) CD123(+) HLA-DR+/st+ CD4(-) CD45dim(+); Stage II was the more immature stage displayed a phenotype of CD34(dim+) CD117(dim+) BDCA2(-/dim+) BDCA4(-/dim+) CD123(st+) HLA-DR+/st+ CD4(-) CD45(+); and Stage III was the mature stage showed CD34(-) CD117(-) BDCA2(+)/BDCA4(+) CD123(st+) HLA-DR+/st+ CD4(+) CD45(+/st+). Three maturation-involved stages overlapped well with the phenotypes of normal DC progenitors in a continuously developmental process: granulocyte, monocyte, and DC progenitors (GMDPs) and/or monocyte and DC progenitors (MDPs), common DC progenitors (CDPs), pDCs, and/or pre-DCs. In this study, we considered AML/MDS-pDCs as entities that were distinct from BPDCN and MPDCP and correlated the components of this tumor with the normal DC differentiation pathway, which provides new evidence for understanding DC neoplasms. (c) 2019 International Society for Advancement of Cytometry