A case of carcinosarcoma of the duodenum.

A 59-year-old man was admitted to the hospital because of upper abdominal pain. Endoscopic examination and computed tomography showed a polypoid tumor located in the 2nd portion of the duodenum with invasion to the pancreas head, and biopsy findings suggested a gastrointestinal stromal tumor. He underwent a pancreaticoduodenectomy, and the tumor, which measured 6.5×6.5 cm, was resected. Histologically, the tumor contained two divergent components: differentiated tubular adenocarcinoma and sarcomatoid tissue composed of spindle tumor cells. The tumor directly extended to the pancreas head and metastasized to multiple lymph nodes. The adenocarcinoma cells were positive for AE1/3 and cytokeratin 7 and negative for vimentin. In contrast, the sarcomatoid tissue was negative for epithelial markers and positive for vimentin. The tumor was finally diagnosed as duodenal carcinosarcoma. Duodenal carcinosarcoma is very rare, and only seven cases have been reported to date.