Inverted papilloma of the upper urinary tract.

: Four cases of inverted papilloma in the upper urinary tract are reported-three were located in the ureter and one in the renal pelvis. Clinical and pathological findings are described. In two cases the patients had a history of transitional cell carcinoma; while in one case, inverted papilloma was found in the same lesion as transitional cell carcinoma. The question of malignant transformation of inverted papilloma is discussed. It is concluded that inverted papilloma is a benign tumor with a very low frequency of recurrence, but regular follow-up is advised.