Sarcomatoid collecting duct carcinoma arising in the hemodialysis-associated acquired cystic kidney: an autopsy report.

A case of sarcomatoid collecting duct carcinoma (CDC) arising in a long-term hemodialysis-associated acquired cystic kidney was reported. A 71-year-old woman with a 21-year history of hemodialysis showed a peritoneal metastatic carcinoma (carcinomatous peritonitis) with an unknown primary site. An autopsy revealed a sarcomatoid collecting duct carcinoma of the right kidney with multicyst formation. In addition to the carcinomatous peritonitis, the tumor metastasized to the lymph nodes and bilateral lung. The primary tumor was composed of both carcinomatous and sarcomatous components, suggesting a high-grade transformation. Carcinomatous tumor cells were positive for epithelial membranous antigen (EMA), cytokeratin, and reactive to soybean agglutinin and peanut agglutinin, whereas the sarcomatous cells were positive for vimentin as well as EMA. Thus, the immunohistochemical and lectin-histochemical analysis confirmed that the tumor originated in the medullary collecting duct. Although CDC is not common in acquired cystic kidney disease patients, attention should be given to the occurrence of high-grade carcinoma of rare histological variant, as well as conventional renal cell carcinoma.