Sarcomatoid carcinoma of the ampulla of Vater.

Sarcomatoid carcinomas (carcinosarcomas) are rare lesions in the gastrointestinal tract, where they are most commonly found in the esophagus. We present the first reported case of a sarcomatoid carcinoma of the ampulla of Vater. The tumor was composed of intermixed carcinomatous (adenocarcinoma plus squamous cell carcinoma) and sarcomatous elements. Cytokeratin immunoreactivity was demonstrated focally in the sarcomatoid component, although in other areas there was positive staining for desmin and smooth muscle actin. The possible histogenesis of such lesions is briefly discussed.