Inverted papillomas of the urinary tract. A case of multiple, recurring inverted papillomas of the renal pelvis, ureter and bladder associated with malignant change.

A case of multiple, recurring urothelial inverted papillomas is reported with localization in the bladder, ureter and renal pelvis. Association of several of these with areas of transitional cell tumours and final occurrence of pure transitional cell tumour of papillary and non-papillary type grade II, causes us to question the original concept of inverted papillomas as benign tumours and lean to the more recent concept of inverted papillomas representing precancerous lesions.