CD13

• The principle diagnostic value of CD38 is that its expression is retained and generally increased during differentiation to plasma cells
• CD38 expression has some value in predicting prognosis in CLL
• CD38 is also expressed by committed stem cells together with CD34 and can occasionally be of value in acute leukaemia diagnosis

Normal expression and function

CD13 is an enzyme which cleaves eutral amino acids from the N terminus of small peptides. The function of CD13 appears to vary with the tissue and the precise function in myeloid cells is unclear. The pattern of expression that is similar to other pan-myeloid markers (CD117 and CD33), but with levels generally increasing during maturation (contrasting with CD33 whose expression decreases). Maturation of myeloid cells may be partly identified through the relative CD33/13 expression.

Diagnostic role

• Together with other markers (CD117, CD33 and MPO) CD13 identifies myeloid lineage, particularly acute myeloid leukaemia. CD13 is also found on myelomonocytic and monocytic leukaemias.

• Expression is often absent on more primitive AML, erythroid or megakaryoblastic AML

• Aberrant expression by ALL occurs in around 30% of patients (at the 20% threshold)

• Overall high sensitivity, but may be less specific than CD117 or MPO.

Other relevant information:

Outside the haematopoietic system 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 by acute leukaemias and by haematogones

• Poss.png

  Pro-B ALL

• Poss.png

  Early pre-B ALL

• Poss.png

  Pre-B ALL

• Rare.png

  B ALL

• Rare.png

  Pro-T ALL

• Rare.png

  Mature-T ALL

• Hi.png

  AML

• Freq.png

  Haemato-gones

Notes

In ALL the expression of CD13 is more likely in B-ALL but is also seen in T-ALL

In AML CD13 is expressed in around 80% of cases

In haematogones expression of CD13 is very frequent

Expression by B-lymphoproliferative disorders

• Rare.png

  CLL

• Rare.png

  PLL

• Rare.png

  MCL

• Rare.png

  FL'

• Rare.png

  HCL

• Rare.png

  HCLv

• Rare.png

  MZL

• Rare.png

  LPL

• Rare.png

  PCs

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KEY

The indicated expression frequency, indicates the approximate frequency of occurrence in each particular disease type.

File:Rare.png

rare (<5%)

possible (5-20%)

likely (20-40%)

frequent (40-80%)

expected (>80%)

Where expression level is unusual or characteristic of a disorder this is indicated by text:

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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