The “Jist” of It: Transgastric EUS-Guided Diagnosis of Small Bowel GIST Masquerading as a Peripancreatic Lymph Node

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Purpose: A 76 y/o female with a history of coronary artery disease had an episode of mild pancreatitis managed conservatively. There was no biliary, toxic, or dyslipidemic etiology, and she denied jaundice, weight loss, diabetes, or steatorrhea. After a second episode 8 months later, a CT scan was acquired, revealing a cystic lesion in the body of the pancreas. She was therefore referred for EUS. This showed a 17×8 mm anechoic lesion in the body of the pancreas with a thin wall and no septae. There was no associated mass, internal debris, or chronic pancreatitis, and both the common bile duct and pancreatic ducts were normal; FNA was performed. Incidentally noted was a 24×11 mm peripancreatic solid lesion resembling a lymph node (see image). A transgastric approach was then undertaken for both FNA and Trucut core biopsy. The FNA of the cystic lesion stained positive for mucin, fluid CEA was 1637 ng/mL, and the cytology was negative, all consistent with a mucinous cystadenoma (MCA). The FNA of the peripancreatic mass was unrevealing, but the core biopsy had foci of spindle cells that stained positive for c-kit, strongly suggesting GIST. The patient underwent an enucleation of the cystic lesion and a resection of a submucosal lesion in the fourth portion of the duodenum. Surgical pathology confirmed pancreatic MCA and small bowel GIST. In retrospect, the patient denied any bleeding or obstructive symptoms; review of the prior CT also failed to demonstrate any small bowel lesion. This case highlights the discovery of a small bowel GIST found incidentally on endosonography due to the serendipitous location of the distal duodenal tumor immediately adjacent to the greater curvature of the stomach. GISTs are relatively uncommon, with a prevalence of about 15/million, only 20% of which are found in the small bowel. The rate of malignancy is usually low, but in small bowel GIST, about 50% of lesions are malignant. They are classically subepithelial with central umbilication and positive immunohistochemistry for c-kit. The therapy for these tumors is resection if not metastatic; otherwise, tyrosine kinase inhibitors can be used.[figure1]Figure