Multilocular cystic nephroma in an adult: immunohistochemical study.

We report a case of multilocular cystic nephroma (cysts of the kidney). The tumor was enucleated surgically. It was well encapsulated, and composed of numerous cysts and cellular stroma. Microscopically, the stromal cells resembled blastematous cells seen in Wilms tumor. Immunohistochemical studies disclosed that the stromal cells resembled leiomyocytes, since vimentin and desmin were positive, and myoglobin was negative. An ultrastructural study supported these findings. The characteristics of these cells were compatible with those of congenital mesoblastic nephroma, which also is considered a metanephric tumor.