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Difference between revisions of "CD117"

From www.haemtologyetc.co.uk

 
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Latest revision as of 15:09, 10 October 2019


A widely expressed molecule that is principally employed as a marker of primitive myeloid cells
  • Expression of CD117 by primitive neoplastic cells contributes to a diagnosis of AML
  • Expression is absent in a proportion of typical AML cases (20-30%)
  • There is recognised aberrant expression by up to 30% of ALL cases (more often T lineage)
  • CD117 is expressed by mast cells, and weakly on some plasma cells



Normal expression and function

The German biochemist Axel Ullrich described the molecule in 1987 as the cellular homolog of the feline sarcoma viral oncogene v-kit (c-kit). The CD117 ligand (stem cell factor) binds to CD117 at the cell surface initiating signals that variously control apoptosis, differentiation, proliferation, chemotaxis, or cellular adhesion. CD117 is expressed by early haematopoietic progenitor cells (including those committed to lymphoid lineages) then is lost as the cells mature. It is also expressed by normal mast cells and by normal or neoplastic plasma cells (expression on a proportion of cases that is not strong).


Diagnostic role

  • In acute myeloid leukaemia expression includes 70-80% of cases including less differentiated forms, expression is seen in all subtypes but is less likely in cases with monocytic, erythroid or megakaryocytic maturation
  • Aberrant expression in lymphoid leukaemias: is reported more frequently in T-lineage ALL, particularly early forms; expression in B-lineage ALL is less frequent (5%).
  • Expression in mature B cell malignancies or mature T cells is rare, although CD117 expression is described on some CD8 positive mature T cell neoplasms.
  • Around 30% myeloma express CD117, but often expression is weak which limits its value in this disorder; CD117 can be used to identify mast cells, but does not distinguish normal from neoplastic cells.


Other relevant information:

Outside of the haematopoietic system CD117 has a wide expression: this includes germ cells, Cajal cells (gastrointestinal tract) and epithelial cells in skin adnexa, and breast. Gain-of-function mutations result in tumours affecting: mast cells/myeloid cells (systemic mastocytosis or acute myeloid leukemia); germ cells (seminoma); or Cajal cells (gastrointestinal stromal tumors - GISTs).



SUMMARY TABLES


Expression by acute leukaemias and by haematogones

Notes

  • In ALL the expression of CD117 is more likely in B-ALL but is also seen in T-ALL
  • In haematogones expression of CD117 is very frequent


Expression by B-lymphoproliferative disorders




KEY


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


Rare.png

rare (<5%)

Poss.png

possible (5-20%)

Mod.png

likely (20-40%)

Freq.png

frequent (40-80%)

Hi.png

expected (>80%)


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