BPDCN
From haematologyetc.co.uk
Blastic plasmacytoid dendritic cell neoplasm (BPDCN)
Morphologically the primitive cells may resemble monocytic AML and typically lie in the "blast area" with dim to moderate CD45 expression with low side scatter which can raise the possibility of an AML diagnosis. A skin rash is present in most cases.
Potential difficulties in diagnosis:
The most common source of confusion is with the diagnosis of monoblastic AML: the cells have a primitive phenotype with CD7 and TdT frequently expressed. BPDCN cells will not express MPO. However, expression of CD33 is relatively common with CD117 also expressed in some cases, this allows potetial assignment to the AML category.
What to look for:
Bright expression of: CD56 is generally accompanied by CD36, CD38, CD43, CD71, and HLA-DR, To confirm the diagnosis look also for plasmacytoid dendritic cell (PDC) associated markers: CD123, CD303, CD304, TCF4, TCL1 .
WHO diagnostic criteria allow BPDCN to be diagnosed:
- in the presence of CD123 and one other PDC-associated marker in addition to CD4 and/or CD56,
- in 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.