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Flow Cytometry:B-lymphoid lineage assignment: Difference between revisions

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| colspan="1"''|[[Flow cytometry:MPAL|Return to previous page]]''
| colspan="1"''|[[Tables of diagnostic markers supporting lineage assignment in AML|Return to previous page]]''
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<div id="MPAL_Table2">'''Table 2'''</div>
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'''B-LYMPHOID LINEAGE ASSIGNMENT'''
‎<span id="anchor_0">‎</span>.
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!colspan="2" <span style="font-size:90%; font-color:navy; style="text-align: left; border: 1px solid black; background:pale gray">|'''Requirements to assign B-lymphoid lineage in MPAL'''</br></span>
!colspan="2" <span style="font-size:90%; font-color:navy; style="text-align: left; border: 1px solid black; background:pale gray">|'''Requirements to assign B-lymphoid lineage'''</br></span>
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<div class="mw-collapsible mw-collapsed" data-expandtext="Click for explanation" data-collapsetext="Hide explanation">
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|colspan="2" style = "font-size:90%; color:black; background:#ddeee1" |'''Marker option 1'''
|colspan="2" style = "font-size:90%; color:black; background:#ddeee1" |'''Marker option 1'''
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|colspan="1" style = "font-size:90%; color:black;"|'''Required''' [[CD19|Strong expression of CD19]]</br>'''Required also''' ONE of either: [[CD10]], [[CD22]], or [[CD79a]] (surface or cytoplasmic)
|colspan="2" style = "font-size:90%; color:black;"|'''Required''' [[CD19|Strong expression of CD19]]</br>'''Required also''' ONE of either: [[CD10]], [[CD22]], or [[CD79a]] (surface or cytoplasmic)
|colspan="1" style = "font-size:90%;"|To meet the definition of "strong" the expression, the intensity of CD19 '''must exceed''' that of 50% of normal B lymphocytes
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|colspan="2" style = "font-size:90%; color:black; background:#ddeee1" |'''Marker option 2'''
|colspan="2" style = "font-size:90%; color:black; background:#ddeee1" |'''Marker option 2'''
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|colspan="1" style = "font-size:90%; color:black;"|'''Required''' [[CD19|Weak expression of CD19]]</br>'''Required also''' TWO of either: [[CD10]], [[CD22]], or [[CD79a]] (surface or cytoplasmic)
|colspan="2" style = "font-size:90%; color:black;"|'''Required''' [[CD19|Weak expression of CD19]]</br>'''Required also''' TWO of either: [[CD10]], [[CD22]], or [[CD79a]] (surface or cytoplasmic)
|colspan="1" style = "font-size:90%;"|To meet the definition of "weak" the expression intensity of CD19 must be '''less than''' that of 50% of normal B lymphocytes
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|colspan="2" style = "font-size:90%; color:black; background:#ddeee1" |'''Marker option 3'''
|colspan="2" style = "font-size:90%; color:black; background:#ddeee1" |'''Marker option 3'''
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|colspan="1" style = "font-size:90%; color:black;"|[[CD19|CD19 is not expressed]]</br>'''In this rare occurrence then requires''' THREE of either: [[CD10]], [[CD22]], or [[CD79a]] (surface or cytoplasmic)
|colspan="2" style = "font-size:90%; color:black;"|[[CD19|CD19 is not expressed]]</br>'''In this rare occurrence then requires''' THREE of either: [[CD10]], [[CD22]], or [[CD79a]] (surface or cytoplasmic)
|colspan="1" style = "font-size:90%;"|This is a rare occurrence and should be carefully considered
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<span style="font-size:85%;>'''Notes on interpretation of B-lineage'''</br>
<span style="font-size:85%;>'''Notes on interpretation of B-lineage'''</br>
CD19 is considered by WHO to have high but not complete specificity for B-lineage. Its’ use requires the intensity of expression to be considered: “strong” CD19 expression should exceed 50% of the level seen on normal B progenitors in at least some of the leukaemic cells, while weaker CD19 expression has lower specificity and requires stronger additional evidence of B-lineage commitment (see Table above). Note also: (1) CD79a has frequent expression in T-LL/LBL, so should not be used to suggest B-lineage if that disorder is considered. (2) PAX5 identified by immunohistochemistry has a low evidence base in MPAL diagnosis so should be interpreted with caustion. (3) In the absence of CD19 expression, B-lineage may still be assigned if three other B antigens are expressed.</br>
CD19 is considered by WHO to have high but not complete specificity for B-lineage. Its’ use requires the intensity of expression to be considered: “strong” CD19 expression should exceed 50% of the level seen on normal B progenitors in at least some of the leukaemic cells, while weaker CD19 expression has lower specificity and requires stronger additional evidence of B-lineage commitment (see Table above). Note also: (1) CD79a has frequent expression in T-LL/LBL, so should not be used to suggest B-lineage if that disorder is considered. (2) PAX5 identified by immunohistochemistry has a low evidence base in MPAL diagnosis so should be interpreted with caustion. (3) In the absence of CD19 expression, B-lineage may still be assigned if three other B antigens are expressed.</br>
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Latest revision as of 20:19, 5 January 2024


Requirements to assign B-lymphoid lineage


For B-lymphoid lineage assignment the key lineage-marker is CD19. However, this marker has recognised expression in many cases of otherwise typical AML cases so additional criteria of expression intensity it is required that other markers must be expressed in addition to allow B-lineage assignment. Rarely CD19 is absent in which case a laregr number o other B-cell markers is required.

Marker option 1
Required Strong expression of CD19
Required also ONE of either: CD10, CD22, or CD79a (surface or cytoplasmic)
Marker option 2
Required Weak expression of CD19
Required also TWO of either: CD10, CD22, or CD79a (surface or cytoplasmic)
Marker option 3
CD19 is not expressed
In this rare occurrence then requires THREE of either: CD10, CD22, or CD79a (surface or cytoplasmic)

Notes on interpretation of B-lineage
CD19 is considered by WHO to have high but not complete specificity for B-lineage. Its’ use requires the intensity of expression to be considered: “strong” CD19 expression should exceed 50% of the level seen on normal B progenitors in at least some of the leukaemic cells, while weaker CD19 expression has lower specificity and requires stronger additional evidence of B-lineage commitment (see Table above). Note also: (1) CD79a has frequent expression in T-LL/LBL, so should not be used to suggest B-lineage if that disorder is considered. (2) PAX5 identified by immunohistochemistry has a low evidence base in MPAL diagnosis so should be interpreted with caustion. (3) In the absence of CD19 expression, B-lineage may still be assigned if three other B antigens are expressed.

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