MPAL
From haematologyetc.co.uk
Assignment of category to ambiguous cases in acute leukaemia:
Final lineage requires integration of additional molecular features; assignments made by flow are therefore "provisional" pending full molecular assessment. Four categories may be assigned:
- My/B
- My/T**
- T/B
- Undiff
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Requirements to assign myeloid lineage in MPAL
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Marker 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. |
marker 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: By flow cytometry: CD11c, CD14, CD64; by other approaches: raised lysozyme in serum or urine or non-specific esterase in malignant cells (enzyme cytochemistry) |
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Requirements to assign B-lymphoid lineage in MPAL
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Marker option 1 | |
Required Strong expression of CD19 | To meet the definition of "strong" the expression intensity must exceed that of 50% of normal B lymphocytes |
In addition 1 of: CD10, CD22, or CD79a (surface or cytoplasmic) | If CD19 is strong then B-lineage can be assigned if there is at least ONE of these additional markers |
Marker option 2 | |
Required Weak expression of CD19 | To meet the definition of "weak" the expression intensity must be less than that of 50% of normal B lymphocytes |
In addition 2 of: CD10, CD22, or CD79a (surface or cytoplasmic) | If CD19 is weak then B-lineage can be assigned only if there are at least TWO of these additional markers |
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Requirements to assign T-lymphoid lineage in MPAL
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Marker requirement | |
Either CD3 surface or cytoplasm (strong) | To meet the definition of "strong" the expression intensity must exceed that of 50% of normal T lymphocytes |
Or CD3 by immunocytochemistry (strong) | For immunohistochemistry it is important a non-zeta chain reagent is used |
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What features must be met to diagnose acute undifferentiated leukaemia
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Requirement 1 | |
Required No lineage assignment can be made based on lineage defining myeloid, B-lymphoid or T-lymphoid msrkers i.e. do not express MPO, CD3, strong CD19, cyCD22 or cyCD79a | |
Requirement 2 | |
No more than one lineage-associated (but not lineage-defining marker) for any lineage should be expressed | |
Requirement 3 | |
Markers mainly associated with the primitive nature of leukaemic cells do not allow lineage assignment (e.g. CD34, HLA-DR, TdT, CD7, CD38) and are frequently seen in undifferentiated acute leukaemia | |
Requirement 4 | |
It is essential that other conditions that may resemble undifferentiated acute leukaemia are excluded: these may particu;arly include: acute megakaryocytic leukaemia, non haematopoietic tumours, blastic plasma cell dendritic neoplasm, and rarely plasma cell leukaemias. In each case this may require consideration of the wider context of the clinical history and marker pattern. |