Gastrointestinal stromal tumor of the duodenal ampulla: Report of a case

We report herein the case of a 77-year-old woman with a gastrointestinal st romal tumor (GIST) of the duodenal ampulla. The tumor. which was removed by pancreatoduodenectomy due to its malignant potential, showed expansive gro wth in the muscular coat of the duodenal ampulla. Histologically, the tumor cells were spindle-shaped or round, and exhibited fascicular or storiform growth pattern with frequent mitotic figures. The immunohistochemical and u ltrastructural results suggested that the tumor may have originated from th e interstitial cells of Cajal in the muscular coat of the duodenal ampulla. To our knowledge, this is the first case of malignant GIST of the duodenal ampulla to be reported in Japan.