CLEAR-CELL UNILOCULAR AND MULTILOCULAR RE NAL CYST 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 featu res, pathological diagnosis often being very difficult by cytology and on frozen sections; unilocular cyst resembling a simple renal cyst, t hat 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 cys tic tumor was made possible only by systematic histological examinatio n of all ordinary-looking renal cysts. A four year experience with a s eries of 255 kidneys is presented here. A simple histogenetic schema f or cystic clear cell tumors is proposed. The new types of clear cell l esions presented here : clear cell cyst and a particular type of in si tu intratubular carcinoma, are discussed in reference to multifocal tu mors of the kidney.