[Can inverted papilloma in urinary bladder be considered as a benign tumor]

Inverted papilloma of the urinary bladder is a rare entity. According to literature data, this disease is not malignant, and has low recurrence rate. Authors studied cases detected at the Urology Department and Urooncological Centrum at Semmelweis University in the last 11 years. They aimed to find out the rate of inverted papilloma recurrences, and transformations into malignant bladder cancer.

Thirty patients with histologically proven inverted papilloma were followed after transurethral resection of bladder, which meant urine tests every three months, abdominal ultrasound and cystoscopy. After a year, these examinations were done in every six months.

Three patients presented transitiocellular carcinoma (17, 60, 92 months later) during this period. In one case, inverted papilloma and transitiocellular tumor (pTa G1) were detected. In one patient, inverted papilloma was found by control cystoscopy after transurethral resection of bladder (pT1 G2) and local chemotherapy 15 months later.

Based on authors' experience, inverted papilloma of the urinary bladder is a benign lesion, but malignant changes or concomitant transitiocellular tumor may occur, thus follow-up is needed. Although references are not standardized, authors suggest following patients with inverted papilloma as a primary (pTa G1) bladder cancer.