Flow Cytometry:B-lymphoid lineage assignment in MPAL
From haematologyetc.co.uk
Requirements to assign B-lymphoid lineage
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Marker option 1 | |
Required Strong expression of CD19 Required also ONE of either: CD10, CD22, or CD79a (surface or cytoplasmic) | |
Marker option 2 | |
Required Weak expression of CD19 Required also TWO of either: CD10, CD22, or CD79a (surface or cytoplasmic) | |
Marker option 3 | |
CD19 is not expressed In this rare occurrence then requires THREE of either: CD10, CD22, or CD79a (surface or cytoplasmic) |
Notes on interpretation of B-lineage
CD19 is considered by WHO to have high but not complete specificity for B-lineage. Its’ use requires the intensity of expression to be considered: “strong” CD19 expression should exceed 50% of the level seen on normal B progenitors in at least some of the leukaemic cells, while weaker CD19 expression has lower specificity and requires stronger additional evidence of B-lineage commitment (see Table above). Note also: (1) CD79a has frequent expression in T-LL/LBL, so should not be used to suggest B-lineage if that disorder is considered. (2) PAX5 identified by immunohistochemistry has a low evidence base in MPAL diagnosis so should be interpreted with caustion. (3) In the absence of CD19 expression, B-lineage may still be assigned if three other B antigens are expressed.