We experienced a case of true carcinosarcoma of the esophagus with osteosar
coma. Computed tomography scan revealed calcification of the tumor. Immunoh
istochemically, vimentin staining was positive, and osteoid formation was f
ound in the sarcomatous portion. It was clear that the lesion contained ost
eosarcoma of mesenchymal origin, and thus we diagnosed it as true carcinosa
rcoma.