A protein found on the surface of many different types of cells. It binds to a substance called stem cell factor (SCF), which causes certain types of blood cells to grow. CD117 may also be found in higher than normal amounts, or in a changed form, on some types of cancer cells, including gastrointestinal stromal tumors and melanoma. Measuring the amount of CD117 in tumor tissue may help diagnose cancer and plan treatment. CD117 is a type of receptor tyrosine kinase and a type of tumor marker. Also called c-kit and stem cell factor receptor.