Inverted papilloma of the urinary bladder shows fluorescence on photodynamic diagnosis using 5-aminolevulinic acid

Photodynamic diagnosis (PDD) of non-muscle invasive bladder cancer using 5-aminolevulinic acid (5-ALA) has recently attracted attention as a diagnostic method for observing cancer lesions based on fluorescence emission using a fluorescent endoscope. However, there are few reports of false positives associated with benign bladder neoplasms. Here, we provide report of two cases of inverted papillomas of the bladder that were fluorescent on PDD using 5-ALA. In each case, a surface-smooth, pedunculated bladder tumor was observed, which fluoresced red on PDD after oral administration of 5-ALA. Histopathological findings demonstrated inverted papilloma of the bladder. Although inverted papilloma of the bladder is usually regarded as a benign neoplasm, some recent studies have revealed that it could be a risk factor for urothelial carcinoma. Our present report may support the hypothesis that inverted papilloma of the bladder has malignant potential.