Inverted papilloma: urothelial tumor of benign biologic potential

Inverted papilloma of urinary bladder: Is long-term cystoscopic surveillance needed? A single center’s experience

OBJECTIVES

To review all cases of urinary bladder inverted papilloma (IP) in our institution and determine the need for cystoscopic surveillance. IP is an uncommon benign tumor of the urinary tract. Its multiplicity, recurrence, and association with transitional cell carcinoma (TCC) suggest possible malignant potential, leading to conflicting clinical conclusions regarding the need for surveillance.

METHODS

All consecutive patients from January 1991 to December 2004 with IP were included in this study. A single pathologist performed the histologic review. The patients had undergone cystoscopy and ultrasound evaluation of the kidneys every 6 months.

RESULTS

Of the 52 patients, 45 were men and 7 were women. The average age at presentation was 58.9 +/- 11.8 years (range 30 to 79). No patient had a synchronous or previous bladder tumor. The most common complaint was macroscopic hematuria. Ten cases were incidental findings during bladder ultrasonography or cystoscopy. All were solitary tumors, most commonly found at the bladder neck. The average follow-up period was 62 +/- 23 months, with no recurrence. One case of subsequent noninvasive papillary TCC developed 15 months later. The initial histologic findings had revealed cytologic atypia, with suspicious urine cytology findings. On review, it was more compatible with TCC with an inverted pattern.

CONCLUSIONS

Although our cases exhibited benign biologic behavior, the presence of cytologic atypia and suspicious urine cytology require exclusion of TCC with an inverted pattern. Thus, in histologically proven solitary bladder IP with no associated TCC, cystoscopic surveillance may not be necessary.

IS SURVEILLANCE NECESSARY FOR INVERTED PAPILLOMA IN THE URINARY BLADDER AND URETHRA?

BACKGROUND

A case series of inverted papilloma of the urinary bladder and urethra is presented, together with a review of the literature with respect to multiplicity, recurrence rate and association with transitional cell carcinoma, and a discussion on surveillance of the lesion.

METHODS

Cases of inverted papilloma of the lower urinary tract in a single centre were reviewed. Patient and tumour characteristics, recurrence and associated transitional cell carcinoma are reported.

RESULTS

Twenty patients were included (18 male, two female). The mean age was 60.8 years (range 35-78 years). All had solitary tumours ranging from 3 mm to 30 mm in size. Median cystoscopic follow up was 30 months (range 2-140 months). There was no recurrence. One patient was associated with subsequent transitional cell carcinoma 44 and 76 months later. Together with the present 20 cases, review of the English literature with respect to inverted papilloma of the lower urinary tract identified a total of 322 cases reported, with a recurrence rate of 3.85%. Moreover, 1.55%, 5.90% and 1.54% were associated with previous, simultaneous and subsequent transitional cell carcinoma, respectively.

CONCLUSIONS

Recurrence is not uncommon and risk of subsequent transitional cell carcinoma is not rare, such that non-invasive surveillance with flexible cystoscopy is recommended for inverted papilloma of the lower urinary tract.

Clinical Studies on Inverted Papilloma of the Urinary Tract: Report of 48 Cases and Review of the Literature

PURPOSE

We report on 48 clinicopathologic cases of inverted papilloma and present the clinical significance attributed to these lesions in terms of the current literature.

MATERIALS AND METHODS

From 1976 to 2002 we had experience with 48 cases of inverted papilloma in urinary tract. We present the clinical features of these cases and report the results of prognosis research.

RESULTS

Patient age ranged from 24 to 82 years (mean 56). Coexistence of transitional cell carcinoma occurred in a different location in the bladder in 3 cases and within a single neoplasm in the ureter in 2. Followup data were available in 42 of the 48 cases. Followup ranged from 8 months to 23 years 6 months (mean 8 years 1 month). Of the 42 cases 3 (7%) had a recurrence and range from initial resection at 5 months, 1 year 4 months and 2 years 6 months, respectively.

CONCLUSIONS

Our study suggests that there are 2 types of urinary inverted papilloma. The lesions in 1 type behave in a benign fashion and in another they have malignant potential. At this time we have no strategy with which to distinguish the 2 types of urinary inverted papilloma. Our results indicate that we must follow all cases for at least more than 2 years after initial treatment.

Multiple simultaneous inverted papillomas of the upper urinary tract. A case report with a review of ureteral and renal pelvic inverted papillomas

An asymptomatic 73-year-old woman was found to have multiple, simultaneous, inverted papillomas of the renal pelvis and ureter. A review of the world literature yielded 34 cases of inverted papillomas in the upper urinary tract: 13 in the renal pelvis, and 21 in the ureter. Among these 34 cases, there were 26 male and five female patients, with gender not given for three others. Patients ranged in age from 19 to 89 years (mean, 64.1 years). Many cases lacked complete clinical details but, among the others, gross painless hematuria was the presenting symptom in seven; hematuria with flank pain or colic in six; and pain without hematuria in six. Only six patients lacked urinary tract symptoms, and three of these had microscopic hematuria. Only two patients had more than one inverted papilloma, and these were not multicentric. Adequate pathologic documentation and follow-up data were, unfortunately, absent in many of the cases. Although inverted papillomas are curable with surgical resection, with a low rate of local recurrence, they appear to be associated with synchronous or asynchronous carcinomas, especially other transitional cell tumors in the urinary tract.

Inverted papilloma of bladder: clinical significance

Based on 15 cases of inverted urothelial papilloma, we present the clinical significance of these lesions in view of the current literature. An inverted papilloma should raise suspicion with respect to the whole urothelial surface. However, approaching every lesion of this type as a (pre-)neoplastic tumor does not seem justified, since 90 percent of all cases reported so far do not present any clinical or histologic feature of malignancy. Some factors, such as the patient's history, eventually associated urothelial carcinomas, or histologic features of malignant transformation within an inverted papilloma, must be taken into consideration. If no single indication in favor of malignancy has been disclosed, we believe follow-up with yearly endoscopic investigations, in addition to regular urine cytologies, may suffice.

Inverted papilloma: observation with scanning and transmission electron microscopy

Three cases of inverted papilloma of the urinary bladder were studied by transmission electron microscopy. Scanning electron microscopic observation was made in one of these. The surfaces of the outer-most tumour cells were covered with short stubby microvilli. Multiple bud like proliferations of the tumour cells were compatible with a trabecular type of inverted papilloma. The tumour cells of the trabeculum mimicked the intermediate and basal cells of the epithelium which covered the surface. Microcysts are believed to be formed by epithelial migration into pits, creating an epithelial inversion, and do not represent central necrosis. Ultrastructure suggests that inverted papilloma is a very well differentiated tumour.

Histology and histogenesis of two different types of inverted urothelial papillomas

Inverted papillomas are rare tumors of the lower urinary tract. Among 1829 reclassified tumors of the urinary bladder, renal pelves, ureters, and urethra, there were 40 (2.2%) inverted papillomas. The great majority of these were localized in the bladder. Because of distinctive histologic features and patterns of growth it is possible to differentiate between two basic types of inverted papillomas which were termed "trabecular" and "glandular." The trabecular type consists of widely branched, anastomosing cords of urothelial cells originating directly from the overlying transitional epithelium. The trabeculae are arranged horizontally or perpendicularly to the surface epithelium and occasionally exhibit peripheral palisading of the cells. The glandular type is characterized by multiple round to oval islands of proliferated urothelial cells together with pseudoglandular and true glandular structures which are often still connected with the surface urothelium. The gland-like structures are lined by stratified urothelium, the true glands by mucus secreting columnar epithelium. Sometimes glandular metaplasia of an intestinal type with goblet cell formation could be observed. Inverted papillomas of the trabecular type arise histogenetically from a proliferation of the basal cells of the urothelium. The glandular type develops apparently from a proliferative cystitis cystica and glandularis which, therefore, should be considered a potentially preneoplastic lesion. The predominant view of the biological behavior of inverted papillomas is that of a benign neoplastic lesion. Morphologic findings supplied some arguments in favor of a low grade malignant potential of these tumors. However, their malignant transformation seemed to be much lower than that of exophytic papillomas.

Inverted papilloma of the urinary tract

We report 9 clinicopathological cases of inverted papilloma. The occurrence of associated true malignant epithelial tumors in the urinary tract in 4 patients is not concurrent with previous reports. Even though inverted papilloma per se is a benign lesion it may be associated with malignant epithelial tumors of the urinary tract. The similarity between proliferative lesions of the bladder and inverted papilloma is discussed. The possibility of common etiologic factors of proliferative cystitis, cystitis cystica, cystitis glandularis, inverted papilloma and ordinary bladder tumors may be considered.

Inverted papilloma of the urinary bladder: ultrastructural and immunologic studies

The histologic, ultrastructural, and immunologic features of an inverted urinary bladder papilloma were studied with thin-section and freeze-fracture electron microscopy, a specific red blood cell adherence test, and through analysis of urine carcinoembryonic antigen (CEA). The increased number of gap junctions and desmosomes, the presence of thickened and reduplicated basal laminae, and the normal CEA levels found in association with this neoplasm, correlate well with its generally predictable benign behavior.

Lobulated inverted papilloma of the ureter

An inverted papilloma of the ureter with ipsilateral hydronephrosis was found in a 77-year-old man who had a history of prostatic carcinoma. Inverted papilloma of the urothelium is a rare lesion, with the vast majority of cases being found in the bladder. To date none has been documented in the ureter.

Inverted papilloma and papillary transitional cell carcinoma of urinary bladder: report of four cases of inverted papilloma, one showing papillary malignant transformation and review of the literature

Four new cases of inverted urothelial papillomas are described and added to the 47 cases previously reported in the literature. Three papillomas present benign gross and microscopic characteristics. The fourth case, however, demonstrates inverted papilloma and papillary transitional cell carcinoma in a single polypoid lesion. This papillary malignant transformation, not previously observed in inverted papillomas, cautions against overconfidence in benign nature of inverted papilloma.

Inverted papilloma of the bladder: a distinct urological lesion

With the addition of six new cases, 104 cases of inverted papilloma of the bladder are reviewed. Pathological and epidemiological characteristics of this distinct bladder lesion are outlined, comparison with transitional cell papilloma is investigated, and recommended therapy and follow-up are offered.