a 50-year - old man presented with a mass in the bladder that was detected during a routine checkup . he had no history of flank pain , urinary tract infection , or urothelial carcinoma . the results of a physical examination , urinalysis , routine blood tests , and urine cytology were normal . computed tomography ( ct ) showed a filling defect and a mass in the left distal ureter without hydronephroureterosis ( fig . 1 ) . cystoscopy showed a polypoid mass protruding from the left ureteral orifice with periodic movement and with an edematous , hyperemic mucosal lesion at its end ( fig . 2 ) . a cystoscopic biopsy revealed urothelial carcinoma , of the nested variant , at the top of the polyp ( fig . the remaining mass was removed by ureteroscopy and the base of the mass was subjected to frozen section analysis . the resected mass had a long , smooth - surfaced stalk with an erosion site at the tip from the previous biopsy site ( arrow in fig . the polyp was covered by normal urothelium and the core was composed of a loose edematous and vascular stroma ( fig . there was no evidence of recurrence on the physical examination , cystoscopy , urine nmp22 level , or ct conducted 3 months postoperatively . most cases occur between the second and fourth decades of life ; such tumors are rare in children and in the elderly . the etiology of ureter polyps is thought to be congenital or acquired with exposure to chronic irritants , such as stones , infection , and inflammation . they more commonly involve the left side ( 65% , 15/23 , two cases were bilateral ) and proximal ureter ( 72% , 18/25 ) in the korean population . kim et al .   reported a bilateral case with over 20 small polyps in the mid - upper ureter . the patients present with either hematuria or flank pain secondary to partial ureteral obstruction . however , if the polyp can move in and out with the urine flow , there may be no symptoms or signs of urinary tract obstruction , as in our case . only two fibroepithelial polyps with urothelial carcinoma and one fibroepithelial polyp with carcinosarcoma have been reported . ours is the first case in the korean population . because the results of urine cytology tests can be false - positive and the gross appearance can be hard to distinguish accurately , it is difficult to make a correct diagnosis preoperatively . in fact , the results of urine cytology were positive in two of the seven reported cases . given the low risk of malignancy , the traditional treatment of ureter polyps is segmental resection with or without endoscopy . if patients have severe hydronephrosis , decreased renal function , or stones , conventional surgery can be considered .
we report an unusual case of a urothelial tumor on a ureteral polyp without hydronephrosis . 
 the patient was a 50-year - old male . 
 he had experienced several episodes of gross hematuria . 
 cystoscopy revealed a tumor that periodically prolapsed into the bladder . 
 the tumor had a smooth - surfaced stalk with an erythematous , edematous lesion at the end . 
 tomography showed a mass and filling defect at the left ureterovesical junction . 
 the results of urine cytology tests were negative . 
 after the tumor was identified as a urothelial carcinoma by frozen biopsy analysis , a ureteroscopic resection was performed . 
 the final pathological diagnosis was urothelial carcinoma arising in a ureteral polyp . 
 no recurrence of the tumor or polyp was observed at the 3-month follow - up . to our knowledge , this is the first report in the korean population of a urothelial tumor arising from a ureteral polyp .