Gastrointestinal stromal malignancy arises from which of the following type of cell?

Gastrointestinal stromal malignancy arises from interstitial cells of Cajal. These are submucosal tumors that are slow growing. Small lesions are found incidentally, but has the capacity to ulcerate and cause impressive bleeding. Large lesions can cause symptoms of weight loss, abdominal pain, fullness, early satiety, and bleeding. Two thirds of these tumors occur in the stomach. Epithelial cell stromal GIST is the most common cell type arising in the stomach, and cellular spindle type is the next most common. Almost all gastrointestinal stromal malignancy express c-KIT (CD117) or the related PDGFRA, as well as CD34. Ref: Schwaz's Principles of Surgery, 9e chapter 26, By Daniel T. Dempsey.