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'''Blastic plasmacytoid dendritic cell neoplasm (BPDCN)'''
<div style="width: 95%">
{| class="wikitable" style="border-style: solid; border-width: 5px; color:black"
|colspan="1" style = "font-size:90%; color:black; background:#ddeee1"|'''Blastic plasmacytoid dendritic cell neoplasm (BPDCN)'''
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Morphologically the primitive cells may resemble monocytic AML, or may have less easy to define or even lymphoid morphology. TA skin rash is present in most cases. This is a rare diagnosis but one that presents some practical diagnostic difficulties since BPDCN is derived from myeloid cells and therefore shares morphological and some immunophenotypic characteristics which may overlap typical AML. It is therefore important that specific features of BPCDN are actively sought in cases where an AML diagnosis is based on expression of two myeloid-associated markers and where there is skin rash and absent CD34 expression. </br></br>
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.</br></br>
On standard diagnostic panels the cases 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 and TdT are frequently expressed. characteristically '''CD34 is absent'''  
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)  
*'''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)  
*However '''one or more myeloid lineage-associated features may be detected''': expression of CD33 is relatively common (x%), CD117 may also be expressed (x%), CD13 may be found (x%). Therefore cases may fit the criteria to assign myeloid lineage.</br></br>
*'''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).
 
</br>Diagnosis is then based on specific criteria:
 
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'''Diagnostic criteria for BPDCN:'''
 
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: .
 
Should express: bright CD56 and/or CD4
 
then
 
BPDCN associate markers:
 
'''CD123 expressed''' and one of: CD303, CD304, TCF4, TCL1


Or
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{| class="wikitable"
'''CD123 not expressed''' but at least three of CD303, CD304, TCF4, TCL1 are expressed and context of negative markers (above) is met
!colspan="2" style = "background:palegrey;border:solid"|For cases meeting the criteria above, then the following are required:</br>
|-
!colspan="2" style = "background:white; font-size:90%; border:solid; "|Cells of BPDCN will express: '''bright CD56 and/or CD4'''
|-
!colspan="2" style = "background:palegrey;border:solid"|Then will also meet either Criteria set 1 '''OR''' Criteria set 2</br>
|-
!colspan="1" style = "background:white;border:solid; font-size:90%;"|Criteria for BPCN (set 1)
!colspan="1" style = "background:white;border:solid; font-size:90%;"|'''CD123 expressed''' together with one of: CD303, CD304, TCF4, TCL1
|-
!colspan="1" style = "background:white;border:solid; font-size:90%;"|Criteria for BPCN (set 2)
!colspan="1" style = "background:white;border:solid; font-size:90%;"|'''CD123 not expressed''' but at least three of CD303, CD304, TCF4, TCL1 are expressed
|}


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'''NOTE also''' other hematologic malignancies may share similar phenotypes, therefore diagnosis requires correlation with morphology, histopathology, clinical information to make a definitive diagnosis

Latest revision as of 13:59, 2 January 2024

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
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