Giant renomedullary interstitial cell tumor.

We report a case of a tumor of the renal medulla. Tumor cells were characteristic of renomedullary interstitial cells as demonstrated by light microscopy, immunohistochemistry and electron microscopy. Such masses are usually small (less than 0.5 cm.) and incidental. This neoplasm, however, was 5.0 cm. in diameter. To our knowledge, our case is unique because of tumor size and because it is the first report of an interstitial cell tumor of the kidney that has been clinically observed and surgically excised.