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

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.

Fig. 1.

 Esophagogastroduodenoscopy showing a bulge in the gastric fundus with an unremarkable mucosa.

Fig. 2.

 Computerized tomography showing a huge abdominal cystic mass.

Fig. 3.

 The resected tumor.

Fig. 4.

 Histologic result showing spindle cell tumor.

Fig. 5.

 Immunohistological result showing positive staining of DOG1.

Video 1  Endoscopic ultrasonography showing the cystic lesion for which fine-needle aspiration was performed.

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Most GISTs are solid tumors and rarely present as cystic lesions upon rapid tumor growth, hemorrhage, or necrosis ¹ . In the present case, a gastric cyst was diagnosed based on preoperative clinical data, including computerized tomography, endoscopic ultrasonography, and fine-needle aspiration, and finally diagnosed as GIST after surgical resection. This case illustrates that GISTs should be considered in diagnosing cystic abdominal lesions.

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