[Prognostic value of inverted papilloma of the lower urinary tract].

Objective: Inverted papilloma of the urothelium accounts for 2.2% of urothelial neoplasms. Its oncologic significance is unclear; its potential for recurrence and/or progression is not well-known. Our experience from 1976 to 1999 is reviewed.

Methods: From 1976 to 1999, 31 patients with urothelial inverted papilloma of the lower urinary tract have been treated in our service: 17 presented previous and/or synchronous association with urothelial carcinoma (group I) and 14 had primary inverted papilloma (group II). The recurrence and progression rates for each group were determined and compared. The overall recurrence and progression rates were also determined. Two patients (one from each group) were lost to follow-up. The remaining 29 patients had a mean follow-up of 51.3 months (range 3-125).

Results: 12 patients (41.4%) showed recurrence in the form of bladder carcinoma; 10 from group I (10/16; 62.3%) and 2 from group II (2/13; 15.4%) (p < 0.05). Mean time to recurrence was 17.9 months (range 3-58). Disease free interval was higher in group II (p < 0.05). Progression to infiltrating tumor was observed in three patients; all three had associated superficial bladder carcinoma (group I). The mean time to progression was 30.7 months (range 18-38). No statistically significant differences were found in the percentage of progression between both groups.

Conclusions: Inverted papilloma of the lower urinary tract showed a high incidence of association with urothelial carcinoma and a high recurrence rate, even in primary tumors. Therefore it should be considered a tumor of low grade malignancy that should be followed regularly.