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Atypical patterns of primitive marker expression in acute myeloid leukaemia: Difference between revisions

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<span style="font-size:90%">'''Table:''' Atypical marker patterns associated with specific AML subtypes</span>


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! colspan="2" style = "font-size:100%; color:black"| '''Table:''' Markers primarily used to confirm primitive nature in AML. &nbsp;
|colspan="1" style = "font-size:90%; color:black; background:#ddeee1"|While blast cells typically cause low side scatter of light and have an expression of CD45 that is lower than normal lymphocytes or monocytes, atypical pattterns may cause difficulty. These are often associated with particular AML subtypes.  
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|colspan="2" style = "font-size:90%; color:black; background:#ddeee1"|The expression of some markers is typically associated with primitive cells and can help recognise the primitive nature of blast cells.</br>Note that these markers may also have some lineage specificity but are not generally used to assign lineage
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|colspan="1" style = "font-size:90%; color:black;" |'''[[CD45]]'''
|colspan="1" style = "font-size:90%;"|'''AML with monocytic differentiation'''</br>In AML with monocytic maturation those primitive cells with more mature monocytic features may show higher side scatter (consistent with their size and cytological features) and some or all of the blast cells may also have high expression of CD45 (comparable with normal or CMML monocytes). In such cases the neoplastic cells may lie in the typical monocyte area, and so are difficult to distinguish from reactive monocytes, or from typical or transforming CMML. It is important to compare with clinical and morphological features to ensure appropriate classification ([[Recognition of blast cells with monocytic differentiation|click for further detail]]).
|colspan="1" style = "font-size:90%;"|A marker expressed by all leukocytes and their precursors. In AML expression is characteristically "weak" i.e. significantly less intense than normal lymphocytes or monocytes. In monocytic AML expression may be stronger, particular in mare mature monocytic forms where expression may resemble normal monocytes.
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|colspan="1" style = "font-size:90%; color:black;" |'''[[CD34]]'''
|colspan="1" style = "font-size:90%;|'''Acute promyelocytic leukaemia'''</br>Cells of APL can vary in size and granularity an will often express a range of side scatter features may resemble those of maturing granulocytic cells, similarly CD45 expression may be similar to maturing granulocytic cells. The distribution of cells will be abnormal however and may variably include cells with wide range light scatter features that differ from those of typical blast cells. It is important to distinguish APL blasts from reactive myeloid cells or (in some cases) from cells of MDS. Morphological examination is essential, but consider also the pattern of additional markers ([[Recognition of APL differentiation|click for further detail]]).
|colspan="1" style = "font-size:90%;"|Frequently expressed by AML blast cells (40-80% of cases) - most often in less differentiated forms of AML. Expression is also seen frequently (and often more strongly) in ALL'''
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|colspan="1" style = "font-size:90%; color:black;" |'''[[CD117]]'''
|colspan="1" style = "font-size:90%;"|'''Other patterns'''</br> While most frequently blast cells with myeloid differentiation form a relatively homogenous group with moderately weak CD45 expression, in some cases very weak expression may be seen, or CD45 may have a broad width of expression. These patterns may more closely resemble the appearances of ALL or even of non-haematopoietic tumours. Stronger CD45 expression may also occasionally be seen.
|colspan="1" style = "font-size:90%;"|Frequently expressed by AML blast cells (70-80% of cases) - where it can support myeloid differentiation, CD117 also has some value in establishing primitive differentiation as it is lost as cells mature'''
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|colspan="2" style = "font-size:90%; color:black; background:light gray" |'''Other markers:''' In the context of a proven AML diagnosis a number of markers may be expressed that reflect the primitive nature of the cells. Some of these are more frequently associated with lymphoid disorders, but providing other criteria for AML are met they should simply be considered to show "primitivness".</br>These include: [[CD38]], [[HLA-DR]], [[TDT]], [[CD7]].
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Latest revision as of 19:16, 2 February 2024



Table: Atypical marker patterns associated with specific AML subtypes

While blast cells typically cause low side scatter of light and have an expression of CD45 that is lower than normal lymphocytes or monocytes, atypical pattterns may cause difficulty. These are often associated with particular AML subtypes.
AML with monocytic differentiation
In AML with monocytic maturation those primitive cells with more mature monocytic features may show higher side scatter (consistent with their size and cytological features) and some or all of the blast cells may also have high expression of CD45 (comparable with normal or CMML monocytes). In such cases the neoplastic cells may lie in the typical monocyte area, and so are difficult to distinguish from reactive monocytes, or from typical or transforming CMML. It is important to compare with clinical and morphological features to ensure appropriate classification (click for further detail).
Acute promyelocytic leukaemia
Cells of APL can vary in size and granularity an will often express a range of side scatter features may resemble those of maturing granulocytic cells, similarly CD45 expression may be similar to maturing granulocytic cells. The distribution of cells will be abnormal however and may variably include cells with wide range light scatter features that differ from those of typical blast cells. It is important to distinguish APL blasts from reactive myeloid cells or (in some cases) from cells of MDS. Morphological examination is essential, but consider also the pattern of additional markers (click for further detail).
Other patterns
While most frequently blast cells with myeloid differentiation form a relatively homogenous group with moderately weak CD45 expression, in some cases very weak expression may be seen, or CD45 may have a broad width of expression. These patterns may more closely resemble the appearances of ALL or even of non-haematopoietic tumours. Stronger CD45 expression may also occasionally be seen.