Recurrence and progression rates of urothelial papillomas of the urinary bladder: long-term clinical follow-up in 52 cases
Creators: name: Amin, Ali
name: Faraj, Shiela F.
name: Chaux, Alcides
name: Turki Al-Hussain
name: Cox, Roni
name: Nagar, Michael
name: Netto, George J.
Publisher: name: F1000Research
Year: 2016

description: BACKGROUND: Approximately one-half of all bladder tumors are noninvasive urothelial neoplasms with the pathologic grade being a substantial prognosticator for these lesions. In 2004, the World Health Organization (WHO) reviewed and adopted the 1998 consensus classification system for urothelial neoplasms developed by the International Society of Urological Pathology (ISUP), aiming to better correlate the morphologic features of these lesions with their clinical outcome. In this system, urothelial neoplasms are divided into invasive and noninvasive, and the latter are further subclassified into urothelial papillomas, papillary urothelial neoplasms of low malignant potential, and low-grade and high-grade papillary urothelial carcinomas. Urothelial papilloma (UP) is a rare tumor of the genitourinary tract, usually seen in younger patients as an isolated, small papillary lesion. It is considered benign with a recurrence rate of 0–31% and little risk of progression. However, most studies are based on a small number of cases. The present study evaluates the long-term clinicopathologic and outcome features in patients with UP that were diagnosed and treated at a single tertiary-care, academic facility after the adoption of the 2004 WHO/ISUP grading system.This is, to the best of our knowledge, the largest series on the long-term follow-up of urothelial papilloma.<br><br>METHODS: All cases with a diagnosis of UP between 1998 and 2009 were retrieved from the in-house as well as consulting surgical pathology service archives of the Johns Hopkins Hospital (JHH). All cases with a history of a higher grade urothelial lesion prior to the initial UP diagnosis were excluded, including papillary and flat lesions like dysplasia. Also excluded were all the cases with a concomitant non-urothelial malignancy. Fifty-two “primary” UP cases were found that formed the current cohort, and were reviewed by two genitourinary pathologists. Electronic medical records were retrospectively reviewed for all cases. On follow-up, “recurrence” was defined as the development of any subsequent neoplastic urothelial lesion in the bladder, while “progression” was defined as the development of any subsequent flat or papillary neoplastic urothelial lesion of higher histological grade or stage. Data was analyzed using the software PASW Statistics version 18.0 (IBM Corp., Somers, NY).<br><br>RESULTS: Recurrence and tumor progression were observed in 3.8% and 30.2% of patients, respectively. Considering tumor progression, the distribution of outcomes was as it follows: low-grade urothelial carcinoma, 11.5%; high-grade urothelial carcinoma, 7.7%; urothelial dysplasia, 5.8%; and papillary urothelial neoplasm of low malignant potential (PUNLMP), 5.8%. No cancer-specific death was observed in this cohort.<br><br>DISCUSSION: The present study shows a low recurrence rate similar to previous studies; however we surprisingly noticed a significantly higher progression rate than previously reported. One problem is that most of the available literature discusses the low grade papillary urothelial lesions altogether, with less focus on the UPs. There are several hypotheses for explaining the difference in the results, including the difference in study population and the definition of recurrence and progression, the subjective interpretation of the diagnostic criteria, and the possible existence of underlying urothelial lesions that may have been poorly sampled. It is noteworthy that due to the absence of a standard follow-up procedure, the long-term follow-up information for the UP patients is difficult to obtain. Compared to other series, the higher incidence rate in our series could be due to the criteria we used to define “progression” and our more strict criteria for diagnosing the initial lesion as well as recurrence/progression during follow-up. Indeed, some authors consider that progression only includes recurrence to a papillary urothelial carcinoma, either invasive or noninvasive. In other series, not all recurrent cases were microscopically evaluated and the diagnosis of recurrence was based solely on cystoscopic findings. In our study, progression was defined as recurrence of disease with any higher grade lesion, either flat or papillary (including dysplasia, PUNLMP, or urothelial carcinomas) and only histopathologically proven cases were included in the study. Nevertheless, limitations of the present series include its retrospective design; some selection bias may also be expected since we have included consult cases along with in-house ones (almost 60% of the cases were retrieved from the consulting service at the JHH).<br><br>CONCLUSIONS: Although none of our patients developed invasive urothelial carcinoma or died of urothelial carcinoma, we found a relatively high rate of recurrence and progression in our UP cohort compared to previous series. The development of a standardized follow-up protocol is encouraged.