[A Case of Intra-Abdominal Desmoid Tumor with Acute Abdominal Pain].

A 70-year-old man was admitted to our hospital with acute abdominal pain. Abdominal CT showed a 6-cm-sized tumor near the third portion of the duodenum, and a duodenal GIST was suspected. Although the abdominal pain was intense and the tumor was suspected to be ruptured, the vital signs were stable; therefore, we initially planned to perform an elective surgery. However, because the pain could not be controlled, the surgery was performed on the 6th day of hospitalization. The tumor appeared to be a duodenal GIST because it was pulling the third portion of the duodenum inwards. It had a strong tendency to infiltrate the surrounding organs; therefore, forced resection of the right colon, which is the surrounding organ, was performed. Pathological findings showed that the resected specimen was a desmoid tumor and the surgical margins were negative. The postoperative course 1 year after surgery was favorable, and no tumor recurrence occurred. We report a case of desmoid tumor, which caused acute abdominal pain.