Tag Archives: CD19

CD79a

CD79a (MB1) is a B-cell marker with a wider range of positivity in the B-cell development spectrum compared to CD20 (mature B-cell phenotype).  CD79a may be expressed on malignant precursor B-cells and terminally differentiated B-cells (PAX-5 is not expressed in terminally differentiated B-cells).  Please note that in the setting of ALL, CD79a is not lineage specific, and up to 50% of T-ALL cases express CD79a.  AML cases with t(8;21) may also show CD79a expression (along with CD19, CD20, and TdT).

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CD19

CD19 is a B-cell marker.  Until recently this antibody has only been available for use in flow cytometry.  Now CD19 is available as an immunohistochemistry (IHC) marker, with similar sensitivity for B-cells to CD20.  The IHC expression pattern is cytoplasmic and membranous.  It is normally expressed on both Precursor B-cells and B-cells.  CD19 combined with TdT would be specific to detect precursor B-cells. CD20 is not expressed on precursor B-cells, but mature B-cell with surface light chain expression (usually).

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