[Cytology and cytogenesis of experimental epithelial kidney tumors]

Nearly all types of epithelial kidney tumors known from human pathology may be induced by chemicals in laboratory animals. Using cytological criteria at least four different tumor types, namely clear/acidophilic (granular) cell tumors, chromophobic and basophilic cell tumors, and oncocytomas may be distinguished. In rats treated for limited time periods (stop experiments) with nitrosamines or streptozotocin, these different tumor types frequently developed concomitantly in the same kidney and bilaterally. The appearance of all types of epithelial tumors was preceded by specific tubular alterations. The preneoplastic tubular alterations emerged after long lag periods; they were characterized by a phenotypic conversion of the renal epithelia. There was no indication of an increased cell proliferation during the period of carcinogen administration under the conditions of the stop experiments used. Four types of preneoplastic tubular lesions could be distinguished each of which appeared to be related to the development of a certain cytogically well defined tumor type: 1. Chromophobic cell tubules sometimes storing glycosaminoglycans; they developed from the proximal nephron and apparently were prestages of chromophobic, perhaps also basophilic tumors, 2. basophilic cell tubules frequently containing small amounts of glycosaminoglycans; they also developed from proximal tubules and are considered precursors of basophilic cell tumors, 3. oncocytic tubules preceded the appearance of oncocytomas; they originated from the collecting duct system and were composed of cells crowded with mitochondria, and 4. clear cell tubules storing glycogen in excess; they also appeared to develop predominantly, if not exclusively, from the collecting duct system and gave rise to clear/acidophilic cell tumors which frequently accumulated lipids, most probably glycolipids, in addition to glycogen. The results of enzyme histochemical and biochemical studies on the different types of preneoplastic and neoplastic renal lesions suggest that neoplastic cell transformation in renal epithelia is closely related to a basic shift in energy metabolism.