Atypical cysts, acquired renal cystic disease, and renal cell tumors in end stage dialysis kidneys.

Hyperplasia and tumors of epithelium are found in "end stage" dialysis kidneys. Epithelial hyperplasia is most conspicuous within "atypical cysts" in which the lining cells are multilayered and occasionally papillary. These features were studied in the kidneys of 66 renal failure patients by means of multiple tissue blocks and serial histologic sections. Atypical cysts were observed in 20 of the 66 cases. Solid or cystic renal cell adenomas were found in nine cases. Six of the cases having adenomas were among the 20 cases having atypical cysts. Tumors occurred in kidneys having atypical cysts, as dintinguished from kidneys without such cysts, with a frequency greater than would be expected to be due to chance alone (P = 0.0106). Renal cell adenomas are found at a younger age in dialysis patients (mean = 41.2 years) than in a control group of autopsies and surgical cases that had not received chronic dialysis (mean = 61.8 years). These observations provide histologic evidence that renal cell neoplasms are prone to develop in relatively young renal failure patients when their uremia is treated by long term dialysis. The studies further indicate that the stimulus for neoplastic growth accompanies a cystic transformation of the kidneys. Kidneys in five cases in the series, although much smaller than normal, were grossly multicystic, corresponding to the recently recognized acquired renal cystic disease. Hyperplastic cells, like those observed in atypical cysts, were present focally along the cyst walls. This form of epithelial hyperplasia, common to both atypical cysts and the multicystic dialysis kidney, may give rise to the renal cell tumors that are reported to occur with increased frequency in acquired cystic disease.