A Case Report of a Sarcomatoid Carcinoma Arising in the Renal Pelvis with Exuberant Osteosarcomatous Element

Sarcomatoid carcinoma is a rare malignant tumor that has both malignant epithelial and mesenchymal components. We describe a sarcomatoid carcinoma arising in the right renal pelvis of a 68-year-old man. The dominant component of the tumor was osteosarcomatous, but there were also focal carcinomatous areas. The sarcomatous tumor cells produced abundant osteoid matrix surrounded by osteoblastic cells. The carcinomatous tumor cells consisted of papillary urothelial carcinoma. Immunohistochemical assay showed that the sarcomatous tumor cells were positive for vimentin and negative for cytokeratin. The papillary urothelial carcinoma was positive for cytokeratin and negative for vimentin. After surgery, the patient underwent adjuvant chemotherapy. Four months later, he presented with recurrence in the right subphrenic area and metastasis in the right middle lobe of the lung.