CD13

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 have some value in indicating monocytic lineage

• Expression of CD34 is not required to diagnose AML - 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 and it is regarded as less specific than 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

CD13 expression: primitive cell types
AML	B ALL	T ALL	ETP ALL	MPAL	Hgns
freq*	freq	strg	strg	freq	strg

notes: abberent expression is seen in ALL, particularly in B-lineage (and is frequent in regenerating haematogones). In the correct context CD13 expression can indicate MPAL or ETP-ALL (see additional information)

CD13 expression: mature B cell neoplasms*
CLL	MCL	FL	MZL	HCL	LPL	PCL
rare	rare	rare	rare	rare	rare	rare

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

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KEY

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

Limited studies

Rare (<5%)

Possible (5-20%)

Likely (20-40%)

Frequent (40-80%)

Expected (80-100%)

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