NTRK1 and intrahepatic cholangiocarcinoma: When a submucosal tumor is found incidentally during upper endoscopy or colonoscopy, the extraluminal extent of disease should be evaluated using CT.[6] The diagnosis of GIST is secured by immunohistochemical staining for the tyrosine kinase receptor KIT (CD 117), which highlights the presence of interstitial cells of Cajal (ICC).