Acute leukaemia types

1 Most often typical AML will express 3 or 4 of these markers; however it is not essential that any is present and some cases may express only one of these.

AML DIGANOSIS: MARKERS OF PRIMITIVE NATURE The first step in AML diagnosis to establish the primitive nature of the abnormal cells, morphology is often central to this, but markers will generally contribute through the detection of a primitive marker expression or profile: (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, allowing their identification. However, it is important also to be aware of other cells that may occupy that area (for further details see this section) and that some forms of AML forms may not fit this pattern - particularly APL and monocytic AML; while So morphology is essential to confirm a primitive appearance and nature (2) It is often also possible to detect markers associated with primitive nature: in AML this is most often CD34, but other markers may contribute.
Useful markers of primitive cells
CD45	Expressed leukocytes and their precursors; in AML expression is "weak" i.e. significantly less intense than normal lymphocytes or monocytes. In monocytic AML expression may be stronger.
CD34	Frequently expressed by AML blast cells (40-80% of cases) - most often in less differentiated forms of AML. Although expression is also frequent (and often stronger) in ALL
Markers that may be helpful in some cases
TDT	Expressed in some cases of AML (5-20%) particularly in less differentiated blast cells, often on a sub-population of cells. More typically associated with ALL.
CD7	Predominantly seen as a T-cell antigen, CD7 tends may be expressed by AML blasts (20-40%) where it most often indicates a more primitive forms or MPAL. CD7 is most consistently a marker of T-lineage (including T-ALL).
AML DIGANOSIS: MARKERS CONFIRMING MYELOID ORIGIN OF BLAST CELLS
	Useful markers of primitive cells
Strong myeloid restriction
MPO	A strong lineage marker for AML (expressed in around 80% of cases) that when detected by flow cytometry is diagnostic of myeloid differentiation (AML or MPAL) although potentially gives less confident evidence on immunocytochemistry.
Moderate myeloid restriction
CD117	An early marker of myeloid lineage seen in around 80% of AML often recognising more primitive forms, aberrant expression in up to 20% of ALL
CD33	A good marker for AML that is often less strongly expressed in monocytic forms
CD13	A good lineage marker for AML aquired a little later, higher than CD13 in monocytic forms
Other markers helpful in detecting myeloid lineage (often in AML subtypes)
These markers have less general value in diagnosis, but can be useful in subtype selection or in cases whwere lineage is ambiguous.
Marker	Comment
CD10	One of tne of the first lineage-markers acquired in AML with good relative specificity
CD11b	One of tne of the first lineage-markers acquired in AML with good relative specificity
CD11c	One of tne of the first lineage-markers acquired in AML with good relative specificity
CD14	A good marker for AML that is often less strongly expressed in monocytic forms
CD64	A good lineage marker for AML aquired a little later, higher than CD13 in monocytic forms