MPAL: Difference between revisions

Revision as of 10:19, 27 July 2023

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Lineage assignments 1 - defining Myeloid lineage in MPAL The assignment of myeloid lineage recognises MPO expression to be a defining marker of myeloid lineage. However MPO is expressed only by around 80% of AML cases the assignment of myeloid lineage can therefore also be made if monocytic lineage can be established, requiring at least of 5 possible lineage markers to be detected (although only 3 of these can be established by flow cytometry).
Myeloid markers option 1
Myeloperoxidase (MPO)	This marker alone is sufficient to establish myeloid lineage provided it meets the intensity definition - intensity should be at least half of that of mature neutrophils in at least of proportion of cells.
Myeloid markers option 2
If MPO does not meet criteria for myeloid lineage, then myeloid lineage may still be assigned through demonstration of monocytic lineage. This can be assigned by the detection of at least two of the following features:
Surface markers of monocytic lineage: CD11c, CD14, CD64 or other recognised features of monocytic differentiation: serum or urinary lysozyme or non-specific esterase (detected by enzyme cytochemistry)

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Lineage assignments 2 - defining B-lymphoid lineage in MPAL For B-lymphoid lineage assignment the key marker is CD19. However, this marker has recognised aberrant expression in AML cases so additional criteria of expression intensity and other marker expression must also be met to allow B-lineage assignment.
Marker combination 1
1. Strong expression of CD19	To meet the definition of "strong" the expression intensity must exceed that of 50% of normal B lymphocytes
2. plus:	There must be additional expression of at least one of the following CD10, CD22, or CD79a
Marker combination 2
If MPO does not meet criteria for myeloid lineage, then myeloid lineage may still be assigned through demonstration of monocytic lineage. This can be assigned by the detection of AT LEAST TWO of the following
Surface markers of monocytic lineage: CD11c, CD14, CD64 or Other recognised features of monocytic differentiation: serum or urinary lysozyme or non-specific esterase (detected by enzyme cytochemistry)

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-<span style="font-size:80%;></br>The first step in AML diagnosis to establish the primitive nature of the abnormal cells:</br>
+<span style="font-size:80%;></br>For B-lymphoid lineage assignment the key marker is CD19. However, this marker has recognised aberrant expression in AML cases so additional criteria of expression intensity and other marker expression must also be met to allow B-lineage assignment.</br>
-<span style="font-size:80%;>'''(1)''' Typically AML blasts have low CD45 expression and cause low side scatter. This means that they form a relatively uniform and distinctive population that is clearly separate from that of lymphocytes on CD45/SSc plots ([[CD45|for further details see this section]]). It is important to realise however also not all AML cases may fit this pattern low CD45/low SSc pattern - particularly [[APL]] and [[monocytic AML]].</br>
-<span style="font-size:80%;>'''(2)''' Additional markers often expressed on myeloid cells may help confirm the primitive nature of the cells: in AML this is most often CD34, although other markers may contribute and are also listed.</br>
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