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|colspan="1" style = "font-size:90%; color:black; background:#ddeee1"|'''Early T precursor acute lympholastic leukaemia (ETP-ALL)'''
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The ETP-ALL/LBL
<span style="font-size:90%;">The immunophenotype of ETP-ALL requires careful consideration – this reflects that the condition was identified using gene expression profiling rather than by immunophenotype. Using immunophenotype to establish the diagnosis is therefore challenging and may underestimate the number of true cases.* and may not be easily separated from ALAL T/my or T-ALL</br></br>To diagnose ETP-ALL the cells need to meet specific criteria. These are given in the table below:</br></span>


The immunophenotype of ETP-ALL requires careful consideration – this reflects that the condition was identified using gene expression profiling rather than by immunophenotype. Using immunophenotype to establish the diagnosis is therefore challenging and may underestimate the number of true cases.* and may not be easily separated from ALAL T/my
Or T-ALL


The approach presently advocated by WHO requires:
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1. Required expression: Cytoplasmic CD3 (may be heterogenous but should be expressed by ≥25% of blasts)
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2. Required expression: One or more myeloid antigen (CD11b, CD13, CD33, CD65, CD117) and/or stem cell antigens (CD34, HLA-DR)
!colspan="2" style = "background:palegrey;border:solid"|'''<span style="font-size:90%;">Requirement 1: Expressed antigens'''</span></br>
3. Required absence: CD3, CD1a and CD8 (<5% of blasts)
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4. Required absent/dim CD5 expression (<75% positive blasts)  
!colspan="2" style = "background:white;border:solid; font-size:90%;"|1. T-lineage should be demonstrated by [[CD3|cCD3]] expression: (may be heterogenous but should be expressed by ≥25% of blasts) [[Flow Cytometry:T-Lymphoid lineage assignment|See assignment of T-Lymphoid lineage in ETP-ALL]]</span></br>
<span style="font-size:90%;">2. One or more myeloid antigen ([[CD11b]], [[CD13]], [[CD33]], [[CD65]], [[CD117]]) and/or stem cell antigens ([[CD34]], [[HLA-DR]]) should be present</span></br></br>
<span style="font-size:90%;">Note CD7 is consistently positive in ETP-ALL and does not count as a stem cell antigen in this context</span>
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!colspan="2" style = "background:palegrey;border:solid; font-size:90%"|'''Requirement 2: Non-expressed antigens'''
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!colspan="2" style = "background:white;border:solid; font-size:90%;"|
<span style="font-size:90%;">1. It is required that the following are absent surface-CD3, CD1a and CD8 (<5% of blasts)</br>
2. CD5 expression should be absent or dim CD5 expression (<75% positive blasts)</span></br>


Note that CD7 is consistently positive in ETP-ALL and does not count as a stem cell antigen in this context
<span style="font-size:90%;">CD4 may have the same pattern as CD5 but is not formally included in the definition</span>
*CD4 may have the same pattern
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The ETP-ALL immunophenotype may also be established by immunohistochemistry.


*T-ALL cases that have an immunophenotype similar to ETP-ALL but where CD5 is expressed (≥75% of blasts) may be designated as “near-ETP-ALL”, but the clinical implications of such a designation remain unclear.
<span style="font-size:90%;">'''NOTES'''</br></span>
<span style="font-size:90%;">1.The ETP-ALL immunophenotype may also be established by immunohistochemistry.</br>2. Distinction from mixed-phenotype acute leukaemia (MPAL) requires that MPO is not expressed - in this context of ETP-ALL the WHO advocate a threshold of <3% to define negative myeloperoxidase expression (by cytochemistry or flow cytometry). This threshold is different from that of T/myeloid MPAL so may not be optimal but is retained at present.
</br>3. T-ALL cases that have an immunophenotype similar to ETP-ALL but where CD5 is expressed (≥75% of blasts) may be designated as “near-ETP-ALL”, but the clinical implications of such a designation remain unclear.</span>


 
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Distinction from mixed-phenotype acute leukaemia (MPAL) requires that MPO is not expressed - in this context of ETP-ALL the WHO advocate a threshold of <3% to define negative myeloperoxidase expression (by cytochemistry or flow cytometry). This threshold is different from that of T/myeloid MPAL so may not be optimal but is retained at present.

Latest revision as of 17:21, 17 January 2024

Early T precursor acute lympholastic leukaemia (ETP-ALL)

The immunophenotype of ETP-ALL requires careful consideration – this reflects that the condition was identified using gene expression profiling rather than by immunophenotype. Using immunophenotype to establish the diagnosis is therefore challenging and may underestimate the number of true cases.* and may not be easily separated from ALAL T/my or T-ALL

To diagnose ETP-ALL the cells need to meet specific criteria. These are given in the table below:


Requirement 1: Expressed antigens
1. T-lineage should be demonstrated by cCD3 expression: (may be heterogenous but should be expressed by ≥25% of blasts) See assignment of T-Lymphoid lineage in ETP-ALL

2. One or more myeloid antigen (CD11b, CD13, CD33, CD65, CD117) and/or stem cell antigens (CD34, HLA-DR) should be present

Note CD7 is consistently positive in ETP-ALL and does not count as a stem cell antigen in this context

Requirement 2: Non-expressed antigens

1. It is required that the following are absent surface-CD3, CD1a and CD8 (<5% of blasts)
2. CD5 expression should be absent or dim CD5 expression (<75% positive blasts)

CD4 may have the same pattern as CD5 but is not formally included in the definition


NOTES
 1.The ETP-ALL immunophenotype may also be established by immunohistochemistry.
2. Distinction from mixed-phenotype acute leukaemia (MPAL) requires that MPO is not expressed - in this context of ETP-ALL the WHO advocate a threshold of <3% to define negative myeloperoxidase expression (by cytochemistry or flow cytometry). This threshold is different from that of T/myeloid MPAL so may not be optimal but is retained at present.
3. T-ALL cases that have an immunophenotype similar to ETP-ALL but where CD5 is expressed (≥75% of blasts) may be designated as “near-ETP-ALL”, but the clinical implications of such a designation remain unclear.

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