"The creeping tumor:" An unusual presentation of upper urinary tract malignancy

Upper urinary tract urothelial malignancy accounts for 5-10% of urothelial carcinomas. Synchronous bladder carcinoma occurs in 2-4% of patients with upper urinary tract tumors. Urothelial malignancy involving the entire upper urinary tract is an extremely rare entity. Most upper urinary tract malignancies are transitional cell carcinomas (TCC), of which the sarcomatoid variant is very rare. These tumors pose a challenge to the radiologist. We herein report a case of TCC involving the entire collecting system of the left kidney, extending down along the ureter and projecting as a mass in the bladder.