BPDCN

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) expresses CD4, CD56 (bright), CD36, CD38, CD43, CD45, CD71, HLA-DR, as well as plasmacytoid dendritic cell (PDC) associated markers (CD123, CD303, CD304, TCF4, TCL1) (2, 18). CD45 expression may range from dim to moderate. SSC of the tumor cells is usually low. CD7 and CD33 are relatively commonly expressed. TdT is positive in approximately one-third of the cases, and occasional cases may express CD117. Based on the WHO diagnostic criteria (2), BPDCN can be diagnosed in the presence of CD123 and one other PDC-associated marker in addition to CD4 and/or CD56, or the presence of three PDC-associated markers and the absence of CD34 and other cell type-specific markers including CD3, CD14, CD19, lysozyme, and MPO. Given the presence of other hematologic malignancies with similar phenotypes, correlation with histomorphology, clinical information and IHC studies is always necessary to make a definitive diagnosis of BPDCN.