Renal cell carcinoma, chromophobe type, with collecting duct carcinoma and sarcomatoid components.

We report a case of a 72-year-old man with a chromophobe renal cell carcinoma that had both sarcomatoid and collecting duct carcinoma components. The 7-cm tumor occupied the entire lower pole of the kidney and infiltrated the renal parenchyma and the pelvic-calyceal system. Histologically, it had an area of classic chromophobe renal cell carcinoma that merged into a sarcomatoid component. Closely intermixed with the sarcomatoid component was a collecting duct carcinoma component characterized by highly pleomorphic, epithelioid cells arranged in cords, nests, and tubulomicrocystic structures. The cords, nests, and tubules were associated with a florid desmoplastic stromal response and numerous inflammatory cells. In addition, dysplastic changes were noted in adjacent nonneoplastic collecting duct epithelium. Immunohistochemical studies confirmed the presence of 3 distinct components in this patient's tumor. To the best of our knowledge, this is the first reported case of a chromophobe renal cell carcinoma with sarcomatoid and collecting duct carcinoma components.