Giant gastric stromal tumor with predominant cystic formation misdiagnosed as gastric cyst under endoscopic ultrasonography and fine-needle aspiration.

Abstract

A 78-year-old man was admitted owing to 10 days of abdominal pain. He had a history of coronary heart disease, diabetes mellitus, and hypertension. Laboratory results, including tumor markers, blood amylase, and lipase, were unremarkable. During physical examination, a mass was palpated in the left upper abdomen (from the left costal arch to the umbilicus), which had an indistinct boundary and was poorly mobile. Esophagogastroduodenoscopy revealed a bulge in the gastric fundus with an unremarkable mucosa ([Fig. 1]). Computerized tomography revealed a huge abdominal cystic mass (23.3 × 14 × 22 cm), which had an indistinct boundary with the stomach ([Fig. 2]), and distinct boundaries with adjacent organs such as the liver, pancreas, etc. Endoscopic ultrasonography revealed a hypoechoic cystic lesion with scarred hyperechoic strip, and fine-needle aspiration was performed ([Video 1]). A rapid on-site evaluation was unremarkable. The cystic fluid analysis revealed a negative stringing test, normal amylase and lipase, slightly elevated CA125 and ferroprotein, with normal CEA, CA199, and AFP. Cell block and immunocytochemistry were also undiagnosed. Surgical resection was performed ([Fig. 3]), and 3000-mL cystic fluids were aspirated intraoperatively. Postoperative histology showed a spindle cell tumor ([Fig. 4]) with necrosis and cystic degeneration, and immunohistochemical results showed positive staining of CD117, DOG1 ([Fig. 5]), and CD34, with negative staining of SMA, S100, and Ki-67 index of 25 %, and mitoschisis of 8/50 HPF. Therefore, the final diagnosis was a high-risk gastrointestinal stromal tumor (GIST). He refused imatinib treatment and died within 2 years.