[A Case of Small Intestinal GIST with Small Intestinal Torsion during Follow-Up as an Ovarian Cyst].

An 87-year-old woman with no prior history of laparotomy visited her local doctor complaining of anorexia. She was diagnosed with intestinal obstruction and initially managed conservatively with fasting; however, her condition did not improve, and she was referred to our hospital on the seventh day after symptom onset. Abdominal CT revealed a 2-cm cystic lesion on the anterior surface of the sacral pelvic cavity and a whirlpool sign near the end of the ileum. Based on these findings, a diagnosis of small intestinal volvulus and an ovarian cyst-previously noted-was made, and emergency surgery was performed on the same day. Intraoperative findings showed no ovarian abnormalities; instead, a lobulated tumor with an extramural cystic growth was identified in the ileum, 210 cm proximal to the anal verge from the ligament of Treitz and 120 cm distal to the ileocecal valve. The small intestine was twisted 360 degrees in a counterclockwise direction around the tumor. There was no evidence of ischemia in the small intestine, and a partial ileal resection including the tumor was performed. Histopathological examination confirmed a diagnosis of gastrointestinal stromal tumor (GIST) of the small intestine. Small intestinal GISTs with cystic features are relatively rare, and there have been scattered reports highlighting the difficulty in differentiating them from ovarian tumors on imaging. Additionally, secondary small bowel volvulus caused by small intestinal GISTs is also uncommon. We report these 2 characteristics of small intestinal GISTs with a review of the relevant literature.