The prognostic value of a primary inverted papilloma of the urinary tract

Purpose: Ever since the recognition of the inverted papilloma as a distinct lesion of the urinary tract, there has been discussion about the possible (pre)malignant potential of this rare tumor, with subsequent uncertainty about followup. Hampering the discussion are the low frequency, the unknown etiology, the difficult histopathological diagnosis and the reported association with transitional cell carcinoma. We reviewed the literature and studied our patients, resulting in the largest series reported in the literature to date. Materials and Methods: We selected 51 patients with an inverted papilloma without a history of or a concordant transitional cell carcinoma of the urinary tract. Histology of all patients was reviewed. Results: After review, as many as 14 patients appeared to be misdiagnosed (transitional cell carcinoma in 11). In 37 patients, we could confirm the diagnosis of inverted papilloma, with characteristics that were highly comparable to those described in the literature. Only 1 patient had a superficial bladder tumor after 49 months. Conclusions: Reviewing these data and, our own results, we conclude that an inverted papilloma does not seem to be a risk factor for transitional cell carcinoma, although inverted papillomas and transitional cell carcinoma appear to be related to some extent. Therefore, frequent and long-term followup does not seem to be necessary provided that there is no doubt about the difficult histological diagnosis.