[Clear cell unilocular and multilocular cystic renal tumors and in situ clear cell intratubular carcinoma].

Clear cell cyst can present as: multilocular cyst (mimicking a cystic nephroma), which is just a multicystic variant of clear cell carcinoma, the right diagnosis often being very difficult to make before final pathological examination; unilocular cyst with atypical clinical features, pathological diagnosis often being very difficult by cytology and on frozen sections; unilocular cyst resembling a simple renal cyst, that is usually small, found incidentally in kidneys removed for renal cell carcinoma (mostly clear cell carcinoma) or sometimes for another pathology. The discovery of this not infrequent type of clear cell cystic tumor was made possible only by systematic histological examination of all ordinary-looking renal cysts. A four year experience with a series of 255 kidneys is presented here. A simple histogenetic schema for cystic clear cell tumors is proposed. The new types of clear cell lesions presented here: clear cell cyst and a particular type of in situ intratubular carcinoma, are discussed in reference to multifocal tumors of the kidney.