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Background to flow cytometric diagnosis

Differentiation to plasma cells involves (in mast cases) the loss of typical pan B-cell markers and surface light chains. The expression of CD45 also differs both within and between cases making standard gating strategies difficult to apply. Cells are most often identified through their co-expression of CD138 with a relatively high expression of CD38, together with the absence of typical B-cell features.

Immunophenotype of plasma cells
CD45 expression
There is no consistent pattern of expression of CD45 although it is most often weak, but may be variable and is occasionally strong.
Major markers useful in plasma cell identification
Marker	Freq	Level	Comment
CD38		-	The relatively strong expression of CD38 is typical of plasma cells
CD138		var	Expression is expected although the intensity can vary
κ/λ			Surface light chain expression is lost (internal will be detected in permeabilised cells)
CD19		-	Expression of CD19 may persist in some cases
Other relevant markers
CD5		-	Uncommon but seen in some cases
CD10		-	Expression may be seen
CD11C		-
CD20		-	Expect expression
CD23		-	Infrequent but reported
CD25		-
CD43		-	Generally not expressed by LPL
CD79b		-	Generally expressed
CD103		-
CD200		-	Detected infrequently|-|}
CD200		-	Detected infrequently
FMC7			Generally expressed

Key to table:

Key to colour code for expression frequency Click for link

Key to expression strength code and use Click for link

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