Pseudotumor of the omentum with a fishbone nucleus.

A 23-year-old Japanese man was admitted with a chief complaint of abdominal pain. He was previously healthy, and his past medical history was unremarkable. Local tenderness and rebound tenderness at McBurney's point were elicited. Abdominal roentgenography was non-diagnostic. Ultrasonography and computed tomography showed a tumor with a central core. Based on a diagnosis of appendicitis with omental inflammation or an omental tumor, laparotomy performed. Intraoperatively, no site of gastrointestinal perforation was detected; however, a 5-cm omental granuloma was identified that proved to have a fishbone nucleus on pathological examination. The postoperative course was uneventful, and upper gastrointestinal endoscopy and barium enema were unremarkable. A large solitary omental pseudotumor is rare, and the clinical course in this case was atypical compared with the usual course of intestinal perforation by a foreign body and formation of an intra-abdominal granuloma.