Other less frequent KIT spots are in exon 13, 17, and 8 and occur in approximately 1 to 2% of KIT-GISTs.30Tumors with exon 13 mutations are most often found in the small intestine, usually have a spindle cell morphology, are slightly larger, and are more aggressive tumors than other types of GIST. Here, KIT is linked to gastrointestinal stromal tumor.