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'''Blastic plasmacytoid dendritic cell neoplasm (BPDCN)'''
''Morphologically the primitive cells may resemble monocytic AML, or may have less easy to define or even lymphoic morphology. The cells typically lie in the "blast area" - with dim to moderate CD45 expression with low side scatter. A skin rash is present in most cases.''
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'''Potential diagnostic difficulties'''
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{| class="wikitable" style="border-left:solid 5px green;border-right:solid 5px green;border-top:solid 5px black;border-bottom:solid 5px black; font-size:90%; color:navy"
BPDCN is derived from myeloid cells and shares some morphological and some immunophenotypic characteristics with typical AML:
| colspan="1"''|[[The flow cytometric diagnosis of AML|Return to previous page]]''
*Features of primitive phenotype: CD7 and TdT are frequently expressed but '''CD34 is most often absent'''
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*Lineage-defining markers should not be expressed: MPO (as well as CD14 and lysozyme), cCD3, and CD19 (as well as CD20, cCD22, CD79a) should not be expressed
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*Myeloid lineage-associated features are often found: 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
*It is therefore important that specific features of BPCDN are actively sought, particularly in cases with skin rash, absent CD34, and where diagnosis is based on expression of two myeloid markers


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'''Diagnostic criteria for BPDCN:'''  
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{| 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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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
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>


then
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).
</br>Diagnosis is then based on specific criteria:


BPDCN associate markers:
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{| class="wikitable"
'''CD123 expressed''' and one of: CD303, CD304, TCF4, TCL1
!colspan="2" style = "background:palegrey;border:solid"|For cases meeting the criteria above, then the following are required:</br>
 
|-
Or
!colspan="2" style = "background:white; font-size:90%; border:solid; "|Cells of BPDCN will express: '''bright CD56 and/or CD4'''
 
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'''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"|Then will also meet either Criteria set 1 '''OR''' Criteria set 2</br>
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!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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