We reported a case of gastrointestinal stromal tumor (GIST) with central cavity formation of the duodenum. A 70-year-old woman was admitted to our hospital because of anemia．Abdominal CT revealed a hyper vascular tumor (10 cm in diameter) with central cavity formation developed extramurally from the second portion of the duodenum. Endoscopic examination revealed a submucosal tumor with central cavity. We observed the inside of a central cavity of the GIST and biopsy specimens were obtained through the endoscope. Histopathorogical examination showed spindle cells arranged in interlacing-bundled pattern. Immunohistochemically, tumor cells were positive for KIT and Vimentin stains, but were negative for CD34, SMA, Desmin and S-100 stains. We diagnosed this case as a GIST of the duodenum, and pylorus preserving pancreaticoduodenectomy were performed. Recent reports indicate the usefulness of tyrosine kinase inhibitor, imatinib mesylate in the treatment of GIST. Additional studies are required to decide the strategy of therapy for GIST.
