CD38

DETAILS

CD38 helps initiate the mobilsation of intracellular calcium, activating a wide array of cell functions that depend on cell type. In haematological cell types CD38 is widely expressed by lymphoid cells and by particular myeloid cells – often in a stage-specific manner. For B lymphocytes CD38 expression is acquired as stem cells commit to B-cell lineage, then lost as mature B cells emerge from bone marrow before being re-acquired by germinal center cells and at the time of plasma cell differentiation. It is also expressed by NK cells and by activated T lymphocytes. CD38 is expressed by most early precursor cells, and by mature monocytes and granulocytes.

What is its diagnostic role?

The major value lies in its use together with CD138, (possibly also CD45 and light-scatter) to identify plasma cells. This may be valuable for diagnosis or monitoring of myeloma. However, CD38 is expressed by both normal and myelomatous plasma cells, and expression may be dimmer on neoplastic plasma cells. Significant CD38 expression (expression by more than 20% of cells) has been shown to predict poor outcome in chronic lymphocytic leukaemia. CD38 is commonly expressed on blasts of any lineage and therefore provides little diagnostic distinction.

Other relevant information: CD38 is a therapeutic target, daratumumab is a monoclonal antibody which binds to CD38 and is used in the treatment of myeloma.

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SUMMARY TABLES

Expression of CD38 by primitive lymphoid cells: ALL and haematogones
pro-B ALL	early pre-B ALL	pre-B ALL	B-ALL	pro-T ALL	mature-T ALL	AML	Haematogones
						*	stg

* low expression correlates with subtype e.g. APML

Expression of CD38 by mature B cells: B-lymphoproliferative disorders
CLL	MCL	FL	HCL	HCv	MZL	LPL	PCL
*		**					stg/mod

*May indicate adverse prognostic when present on more than 20% of cells

**May be weak

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1. Colour key: - the likelihood of any individual case expressing this marker, indicated by colour:

Rare (<5%)

Possible (5-20%)

Likely (20-40%)

Frequent (40-80%)

Expected (80-100%)

2. Text key: - where expression level is characteristic of a disorder this is indicated by text:

abs = absent expression, wk = weak expression, mod = moderate expression, stg = strong expression, sub = expression may be on a sub-population of cells