Inverted papilloma of the urinary tract: histogenesis, recurrence and associated malignancy.

We describe 5 new cases of inverted papilloma of the urinary tract. One case represents the second known recurrence of this tumor while another demonstrated areas of adjacent low grade papillary transitional cell carcinoma. Immunohistochemical studies suggest a histogenetic difference between inverted papillomas of the prostatic urethra and of the bladder.