Premalignant lesions of the urinary bladder

Although most carcinomas of the bladder occur de novo, some vesical lesions progress to malignancy over time. These lesions appear morphologically benign, but often harbour genetic changes that signify their malignant potential. Despite their benign appearance, accurate identification is important given that these patients will require close followup. In addition to this some lesions may mimic carcinoma, and as a consequence, misdiagnosis could result in serious over-treatment. In this review, we discuss the clinical and histological features as well as the differential diagnosis of lesions of the bladder that have the potential to progress to cancer. Specifically, we present the features of flat, papillary and atypical urothelial hyperplasia, urothelial papilloma, urothelial dysplasia, intestinal metaplasia, keratinising squamous metaplasia, verrucous squamous hyperplasia and condyloma acuminatum and examine the molecular and clinical evidence relating to their malignant potential