C-kit (CD117)

C-Kit (CD117) is a proto-oncogene are widely used to help distinguish particular types of tumours. The antibody is primarily used in the diagnosis of Gastrointestinal stromal tumours (GISTs), which are positive for CD117, but negative for markers such as desmin and S-100. These are positive in smooth muscle and neural tumours, which may have a similar histological appearance as GIST. In GISTs, c-Kit staining is typically cytoplasmic, with stronger staining along the cell membranes. C-kit antibodies can also be used in the diagnosis of mast cell tumours and in distinguishing seminomas from embryonal carcinomas. CD117 is important for the classification of mesenchymal tumours of the gastrointestinal tract (including the mesentery). CD117 is expressed in mast cells, melanocytes and interstitial cells of Cajal. Mast cells particularly show a strong membrane as well as cytoplasmic staining (1).

Recommended Controls

Criteria for acceptable staining is a membranous and/or cytoplasmic staining pattern. The recommended positive control to include is a known GIST which is a strong expressor of CD117. A melanoma will be negative and appendix can be used as both a positive and negative control.

Expected staining pattern

GIST

Appendix

Disclaimer

These methods are intended as a guide only. Laboratories that wish to implement these methods should perform internal validation/verification prior to use. The RCPAQAP does not make any claim or warranty for the accuracy or performance of these methods.