MPAL

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Definition of MPAL (WHO) Section 1 - defining Myeloid lineage in MPAL The first step in AML diagnosis to establish the primitive nature of the abnormal cells: (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 (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. (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.
Marker combination 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.
Marker combination 2
If MPO does not meet criteria for myeloid lineage, then myeloid lineage may still be assigned through demonstration of monocytic lineage: AT LEAST TWO of the following markers are expressed: CD11c, CD14, CD64
Alternatively moncytic differentiation may be established through detection of serum or urinary lysozyme; or through cytochemical detection of non-specific esterase