[A case of sarcomatoid carcinoma (undifferentiated carcinoma, sarcomatoid type) of the duodenum].

: A 98-year-old woman with aspiration pneumonia caused by vomiting was admitted to our hospital. Abdominal computed tomography and ultrasonography showed common bile duct dilation and occlusion of the gastrointestinal tract due to a large tumor in the duodenum. Aspiration pneumonia and hepatic failure led to the patient's death. Pathological autopsy showed an 11 × 6 × 2.5-cm polypoid tumor originating from the descending part of the duodenum and involving the common bile duct. Histological examination of the tumor showed mainly spindle cells but also some adenocarcinoma cells. Tumor cells, including spindle cells, were strongly positive for cytokeratin 7; therefore, sarcomatoid carcinoma originating from the duodenum was diagnosed. To the best of our knowledge, only 5 cases of sarcomatoid carcinoma originating from the duodenum have been reported, and they often show polypoid growth. The possibility of sarcomatoid carcinoma should be considered if such findings are noted.