BPDCN
From haematologyetc.co.uk
| Blastic plasmacytoid dendritic cell neoplasm (BPDCN) |
This is a rare diagnosis but one that presents some practical diagnostic difficulties since BPDCN is derived from myeloid cells and therefore may have morphological and immunophenotypic characteristics which overlap with typical AML or acute undifferentiated leukaemia. Morphologically the primitive cells may resemble AML or have lymphoid morphology, and a skin rash is present in most cases. In view of the diagnostic overlap, correlation with morphology, histopathology and clinical information is important when making this diagnosis.
Using standard diagnostic panels, cases of BPDCN generally have the following features:
- BPCDN typically have features of primitive phenotype: the cells typically lie in the "blast area" - with dim to moderate CD45 expression with low side scatter. CD7, TdT, CD38 and HLA-DR are frequently expressed. CD34 is characteristically absent
- Lineage-defining markers of myeloid, T or B cell are not expressed: i.e. there is no expression of MPO, CD14 or lysozyme; cCD3 is not expressed, and CD19 is not expressed (as well as CD20, cCD22, CD79a)
- One or more myeloid lineage-associated features may be detected: expression of CD33 is relatively common (>50%), CD117 may also be expressed (<20%), CD13 may be found although is infrequent (<5%). Therefore cases may fit the criteria to assign myeloid lineage (two myeloid-associated markers).
Diagnosis is then based on specific criteria:
| For cases meeting the criteria above, then the following are required: | |
|---|---|
| Cells of BPDCN will express: bright CD56 and/or CD4 | |
| Then will also meet either Criteria set 1 OR Criteria set 2 | |
| Criteria for BPCN (set 1) | CD123 expressed together with one of: CD303, CD304, TCF4, TCL1 |
| Criteria for BPCN (set 2) | CD123 not expressed but at least three of CD303, CD304, TCF4, TCL1 are expressed |