CD13

Summary

A useful marker of myeloid lineage although expression depends significantly on stage and type of maturation (see Diagnostic Role). CD13 has recognised aberrant expression in some cases of ALL (particularly B-lineage)

Normal expression and function

CD13 is a cell surface enzyme whose function varies between tissues; its precise function in myeloid cells is unclear. The pattern of expression is similar to other pan-myeloid markers (CD117 and CD33), but with levels generally increasing during maturation (contrasting with CD117 and CD33 whose expression decreases). Maturation of normal myeloid cells may therefore be partly idicated through the relative CD33/13 expression.

Diagnostic role

• Together with other markers (CD117, CD33 and MPO), CD13 can be used to identify myeloid lineage in acute myeloid leukaemia.

• CD13 is also expressed by myelomonocytic and monocytic leukaemia cells where a high ratio of CD13/CD33 may help suggest monocytic lineage

• Expression of CD34 is not required to diagnose AML and is not fully specific - CD13 is often absent on more primitive AML cases as well as on those with erythroid or megakaryoblastic differentiation; while aberrant expression in ALL is recognised to occur in around 30% of patients.

CD13 is often regarded as less specific for myeloid lineage than either CD117 or MPO.

Other relevant information:

Expression is not restricted to myeloid cells, and CD13 is particularly expressed on small intestinal and renal tubular epithelial cells and synaptic membranes from the CNS.

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SUMMARY TABLES

Expression in primitive cell types
AML	CMML	B ALL	BL	T ALL	ETP ALL	MPAL	Hgn
80-100%*	80-100%	20-40%**	5-20%	5-20%	20-40%**	20-40%**	80-100%***

Notes: The main application is in AML. Aberrant expression is seen particularly in B-lineage, although it may be less likely in Burkitt lymphoma. CD13 is not generally expressed in T-ALL. CD13 expression can indicate MPAL or ETP-ALL if other markers suggest this.

Expression in mature B cell neoplasms
CLL	MCL	FL	MZL	HCL	DLBCL	LPL	PCL
<5%	<5%	<5%	<5%	<5%	<5%	20-40%	20-40%

Notes: overall expression is uncommon in mature B-lymphoproliferative disorders, but may occur at plasma cell differentiation

Additional note PLL and vHCL are no longer included, click on the name for further information

CD13 expression: mature T cell neoplasms
ATLL	CTCL Sezary	T-PLL	T-LGL	NK-LGL
limited	limited	limited	limited	limited

Notes: There is limited published evidence, but reports suggest expression of CD13 is uncommon in mature T cell malignancy

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