Acute leukaemia types

Acute Myeloid Leukaemia
Markers with value in confirming primitive phenotype (expressed in both AML and ALL) It is important in AML diagnosis to establish the primitive nature of the abnormal cells, some markers can contribute to this: (1) The typically low CD45 expression and low side scatter of most blast cells means that myeloid blast cells tend to form a relatively uniform population that is clearly separated from that of lymphocytes on CD45/SSc plots and is used to identify them in "gating" (please see CD45). Also be aware of AML forms that have do not fit these typical patterns particularly APL and monocytic AML (2) Other markers such as CD34, TdT and CD7 are expressed by "primitive cells" and can help increase diagnostic confidence that blast cells are present - although their presence is not required if other features fit. (3) While not fully specific for any given lineage, in some cases particular primitive markers are more frequently associated with particular lineages so may contribute to lineage assignment in difficult cases (see comments).
Strong role in establishing the primitive nature of AML
CD45	Expressed by all leukocytes and precursors (100% of cases), but in AML expression is "weak" i.e. significantly less intense than normal T cells, B cells 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. Note that expression is also frequent (and often stronger) in ALL
Potential contribution to establishing primitive nature in AML
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	Similar to TdT, although more frequently expressed (20-40%) CD7 tends to be expressed by AML blasts in the more primitive forms. CD7 is most consistently a marker of T-lineage (including T-ALL).
Markers useful in assigning myeloid lineage in AML When present on blast cells|While not expressed by all cases, when detected by flow cytomwtry MPO can be considered to be lineage-defining marker in AML (or establishing myeloid lineage in MPAL).These markers are each expressed by many cases (around 80% for each marker), they have high specificity although abberrent expression in ALL is feequent (overall 10-20% for any individual marker)).
Markers with strong lineage 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.
Markers with moderate lineage restricttion
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