Long-term clinical outcome of inverted urothelial papilloma including cases with focal papillary pattern: is continuous surveillance necessary?

RAS Family Gene Mutations, Clinicopathological Features, and Spread Patterns of Inverted Urothelial Papilloma of the Bladder

Inverted urothelial papilloma (IUP) is a benign neoplasm characterized by a downgrowth of the urothelium beneath the surface of morphologically normal urothelial cells; however, the molecular features of IUP and their association with clinicopathological characteristics are unclear. In this study, we aimed to investigate the mutational landscape, clinicopathological features, genotype-phenotype associations, and spread patterns of IUP. We performed targeted next-generation sequencing of 39 consecutive IUP cases, the largest series investigated to date, and identified oncogenic driver mutations in RAS family genes in 34 cases (87%). HRAS mutations were the most prevalent (28 cases), which included Q61R (15 cases), followed by KRAS (5 cases) and NRAS (1 case) mutations. Characteristic mutations observed in urothelial carcinoma, including those in FGFR3 , TP53 , or the TERT promoter, were absent. HRAS -mutated IUPs were associated with a history of smoking ( P = 0.017) and streaming morphology ( P < 0.001), corresponding to the trabecular subtype. In contrast, all KRAS -mutated IUPs occurred in never-smoking patients ( P = 0.001) and showed cystic changes in morphology ( P = 0.005), corresponding to the glandular subtype. RAS Q61R immunohistochemistry visually revealed the neoplastic nature of the overlying cells and distinct spread patterns of IUP cells within the surface, including pseudoinfiltrative spread. No recurrence or carcinoma development was observed in any of the IUP cases during the follow-up period. Thus, we confirmed the importance of RAS pathway activation in IUP pathogenesis, an association between RAS family gene mutations and IUP subtypes, and the spread patterns of IUP cells within the surface.

Mimickers of Urothelial Carcinoma and the Approach to Differential Diagnosis

A broad spectrum of lesions, including hyperplastic, metaplastic, inflammatory, infectious, and reactive, may mimic cancer all along the urinary tract. This narrative collects most of them from a clinical and pathologic perspective, offering urologists and general pathologists their most salient definitory features. Together with classical, well-known, entities such as urothelial papillomas (conventional (UP) and inverted (IUP)), nephrogenic adenoma (NA), polypoid cystitis (PC), fibroepithelial polyp (FP), prostatic-type polyp (PP), verumontanum cyst (VC), xanthogranulomatous inflammation (XI), reactive changes secondary to BCG instillations (BCGitis), schistosomiasis (SC), keratinizing desquamative squamous metaplasia (KSM), post-radiation changes (PRC), vaginal-type metaplasia (VM), endocervicosis (EC)/endometriosis (EM) (müllerianosis), malakoplakia (MK), florid von Brunn nest proliferation (VB), cystitis/ureteritis cystica (CC), and glandularis (CG), among others, still other cellular proliferations with concerning histological features and poorly understood etiopathogenesis like IgG4-related disease (IGG4), PEComa (PEC), and pseudosarcomatous myofibroblastic proliferations (post-operative spindle cell nodule (POS), inflammatory myofibroblastic tumor (IMT)), are reviewed. Some of these diagnoses are problematic for urologists, other for pathologists, and still others for both. Interestingly, the right identification of their definitory features will allow their correct diagnoses, thus, avoiding overtreatment. The literature selected for this review also focuses on the immunohistochemical and/or molecular data useful to delineate prognosis.

Inverted urothelial papilloma of the upper urinary tract: description of two cases with systematic literature review

BACKGROUND

Inverted urothelial papilloma (IUP) of the upper urinary tract is an uncommon benign tumour that occasionally presents as a polypoid mass causing urinary obstruction. Histologically, IUP is characterised by a proliferating urothelium arranged in cords and trabeculae, in continuity with overlying intact epithelium, and extending into the lamina propria in a non-invasive, endophytic manner. Cytological atypia is minimal or absent. Top differential diagnoses include urothelial carcinoma with inverted growth pattern and florid ureteritis cystica. Although urothelial carcinomas of the upper urinary tract with prominent inverted growth pattern commonly harbour microsatellite instability, the role of the mutator phenotype pathway in IUP development is still unclear. The aim of this study was to describe two additional cases of IUP of the upper urinary tract, along with an extensive literature review.

CASE PRESENTATION

We observed two polypoid tumours originating in the renal pelvis and the distal ureter, respectively. Both patients, a 76-year-old woman and a 56-year-old man, underwent surgery because of the increased likelihood of malignancy. Histology was consistent with IUP and patients are alive and asymptomatic after long-term follow-up (6 years for the renal pelvis lesion and 5 years for the ureter lesion). The tumours retained the expression of the mismatch-repair protein MLH1, MSH2, and PMS2 whereas loss of MSH6 was found in both cases.

CONCLUSIONS

When completely resected, IUP does not require rigorous surveillance protocols, such as those for urothelial carcinoma and exophytic urothelial papilloma. It is therefore important for the surgical pathologist to be aware of this rare entity in order to ensure correct patient management.

Dataset for the reporting of carcinoma of the bladder-cystectomy, cystoprostatectomy and diverticulectomy specimens: recommendations from the International Collaboration on Cancer Reporting (ICCR)

The International Collaboration on Cancer Reporting (ICCR) is a not for profit organisation whose goal is to produce standardised internationally agreed and evidence-based datasets for pathology reporting. With input from pathologists worldwide, the datasets are intended to be uniform and structured. They include all items necessary for an objective and accurate pathology report which enables clinicians to apply the best treatment for the patient. This dataset has had input from a multidisciplinary ICCR expert panel. The rationale for some items being required and others recommended is explained, based on the latest literature. The dataset incorporates data from the World Health Organization (WHO) 2016, and also from the latest (8th edition) TNM staging system of the American Joint Committee on Cancer (AJCC). Fifteen required elements and eight recommended items are described. This dataset provides all the details for a precise and valuable pathology report required for patient management and prognostication. This dataset is intended for worldwide use, and should facilitate the collection of standardised comparable data on bladder carcinoma at an international level.

Clinicopathologic study of 60 cases of urothelial neoplasms with inverted growth patterns: Reclassification by international consultation on urologic disease (ICUD) recommendations

BACKGROUND

Most urothelial neoplasms of the bladder show an exophytic papillary pattern, but some show an inverted growth pattern. In 2004, the World Health Organization (WHO) released a detailed histologic classification system for papillary urothelial neoplasms, but not for inverted forms. The International Consultation on Urologic Disease (ICUD) recommendations of 2012 are applicable to inverted/endophytic papillary lesions as follows: 1) inverted papilloma (IP), 2) inverted papillary urothelial neoplasm of low malignant potential (IPUNLMP), 3) inverted papillary urothelial carcinoma, low grade, non-invasive (IPUCLG-NI), 4) inverted papillary urothelial carcinoma, high grade, non-invasive (IPUCHG-NI), 5) inverted papillary urothelial carcinoma, high grade, invasive (IPUCHG-I). However, only atypical cellular morphology was considered for classification in the 2012 ICUD recommendations, and data to support to validate this new grading system are lacking.

METHODS

Sixty cases of inverted urothelial papillary tumors were classified into 5 categories according to 2012 ICUD and 2016 WHO/ISUP recommendations to evaluate their clinical, pathological, and immunohistochemical characteristics. Two subgroups were defined as subgroup 1, IP and IPUNLMP, and subgroup 2, IPUCLG-NI, IPUCHG-NI, and IPUCHG-I. Clinical features (age, sex, history of urothelial carcinoma, smoking history, size, and multifocality) and histologic features (nuclear pleomorphism, mitotic count, mitosis level, apoptosis, luminal necrosis, trabecular thickening, anastomosing trabeculae, hypercellularity, loss of polarity, peripheral palisading, palisading with central streaming, and discohesiveness) were evaluated. Immunohistochemical stains for CK20, CD44, P53, p16, Ki-67, cyclin D1 and c-erbB2 were performed.

RESULTS

A total of 60 cases were classified as 10 cases of IP, 29 cases of IPUNLMPs, 15 cases of IPUCLG-NI, 4 cases of IPUCHG-NI, and 2 cases of IPUCHG-I. Compared to subgroup 1, subgroup 2 showed larger tumor size, more nuclear irregularity, higher mitotic count (hot spot and per 10 high power fields), more upper level mitosis (>1/2), and more frequent apoptosis, luminal necrosis, surface papillary component, trabecular thickening, anastomosing irregular trabeculae, hypercellularity, loss of polarity, peripheral palisading with central streaming, and discohesiveness, and absence of umbrella cells and urothelial eddies. CK20, Ki67, and c-erbB2 were the only markers that were differently expressed in the two subgroups, with more expression in subgroup 2.

CONCLUSIONS

The 2012 ICUD recommendations are valid to classify inverted papillary urothelial tumors. However, other histologic features besides atypical cellular morphology should also be considered to distinguish subgroup 1 and subgroup 2 inverted papillary urothelial tumors.

SIU-ICUD on bladder cancer: pathology

Many changes have been made during these last years and concepts for understanding bladder cancer have evolved. We make an update with the latest findings of the WHO (World Health Organistaion) 2016, ICCR (International Collaboration on Cancer Reporting) and other official organisms and try to show the latest developments. In this document we provide new consensus guidelines and insights. We kept this document short and concise providing consensus guidelines to clinicians for the best patient care, it should be easy to understand for a non pathologists. We focussed on several burning issues, such as the anatomical and histological understanding of the bladder wall, the prognostic significance of grading and the most challenging problems in staging, we underline our needs from the clinicians such as clinical information, we further discuss the histological subtypes of bladder cancer, which is an extremely important issue in the light of molecular classifications and give prognostic insights. Furthermore, we discuss the ICCR worldwide consensus reporting, urinary cytology with the Paris system and several issues such as frozen section specimen.

Inverted urothelial papilloma: A review of diagnostic pitfalls and clinical management

Inverted urothelial papilloma (IUP) is a rare, non-invasive endophytic lesion that accounts for 1-2% of urothelial tumours. On cystoscopy, IUP appears as a pedunculated/papillary mass with a smooth surface. On microscopy, IUP has an endophytic growth pattern with the bulk of the tumour covered by a superficial layer of urothelium, which can be hyperplastic or attenuated. The cytology should be bland, with uniform, spindled cells arranged in anastomosing trabeculae and cords with peripheral palisading of basaloid cells. Exophytic papillae and mitotic activity should be absent or focal. Pseudoglandular spaces and squamous metaplasia may also be present. There are distinct molecular differences between IUP and urothelial carcinoma (UC). IUP rarely has mutations of FGFR3, homozygous loss of 9p21, or gain of chromosomes 3, 7, and 17, whereas these mutations are frequently seen in UC. In addition, IUP is much less likely to have TERT mutations compared to UC. Immunohistochemistry can also be helpful in distinguishing the two entities as IUP is typically negative for CK20 and has a low Ki-67 proliferation index. Positivity for p53 may be seen in a minority of IUP. IUP can recur and be seen in association with UC. Distinguishing IUP from UC can be difficult due to the similarity between the two entities both on cystoscopy and histology, as up to 25% of UCs will also have inverted growth. Given the morphologic variants of IUP and UC, it is possible for a diagnostic error to occur, which can significantly impact patient management.

The pathology of urinary bladder lesions with an inverted growth pattern

Inverted lesions in the urinary bladder have been the source of some difficulty in urological pathology. The two common ones are von Brunn's nests and cystitis cystic/cystitis glandularis, which are considered normal variants of urothelium. Apart from them, a number of other rare urothelial lesions with inverted growth pattern occur in the urinary bladder. Some of them are only reactive conditions, just as pseudocarcinomatous hyperplasia. Some are benign tumors, namely inverted papilloma. Whereas others are malignant neoplasms, including inverted papillary urothelial neoplasm of low malignant potential (PUNLMP), non-invasive inverted papillary urothelial carcinoma (low-grade and high-grade), and invasive urothelial carcinoma (inverted, nested and big nested variants). Because of the overlapping morphological features of all the inverted lesions mentioned above, even between high-grade invasive carcinoma and pseudocarcinomatous hyperplasia which are only a kind of reactive conditions, it is very important for the surgical pathologist to recognize and be familiar with these inverted lesions in urinary bladder. In this article, we review these spectrums of inverted lesions of the urinary bladder. Emphasis is placed on histogenesis, morphology, differential diagnosis of these lesions, and the pathologic grading of the non-invasive inverted neoplasms, such as inverted papilloma, inverted PUNLMP, non-invasive inverted papillary urothelial carcinoma with low-grade, and non-invasive inverted papillary urothelial carcinoma with high-grade.

A clinical and molecular review of inverted papilloma of the urinary tract: how to handle?

Inverted papilloma (IP) of the urinary tract is classified by the World Health Organisation as a non-invasive urothelial tumour with normal to minimal cytological atypia of the neoplastic cells. During the 1980s, it came under suspicion of having a premalignant or malignant potential and of being concurrent with urothelial cell carcinoma (UCC). This quandary has been proven difficult to solve, due to the fact that IP is very rare and literature mostly consists of case reports with varying levels of information, making strong meta-analyses problematic. New immunohistochemical techniques and genetic approaches are more frequently being used in the attempt to achieve better classifications, prognosis and treatment of lesions hereunder IP. This review will, in our awareness, be the first to combine the knowledge from retrospective studies with these new approaches for determining a possible premalignant potential and concurrency with UCC and subsequently outline a recommendation for follow-up.

MRI Findings of Inverted Urothelial Papilloma of the Bladder

OBJECTIVE

The objective of this study was to characterize MRI findings of inverted urothelial papilloma of the bladder.

MATERIALS AND METHODS

Data pertaining to 16 patients with 18 pathologically proven inverted urothelial papillomas of the bladder who had undergone MRI were retrospectively collected from seven institutions. The shape and surface characteristics of the tumors were evaluated using T2-weighted MR images. In addition, the signal intensity of inverted urothelial papillomas was visually assessed on T1-weighted, T2-weighted, and DW images and on early and delayed phase contrast-enhanced images.

RESULTS

The shape of the 18 inverted urothelial papillomas of the bladder was classified as polypoid with a stalk for 16 tumors (89%) and polypoid without a stalk for two tumors (11%). All stalks were surrounded by urine in the bladder. A total of 15 of the tumor surfaces (83%) were nonpapillary and three (17%) were papillary. All 12 of the inverted urothelial papillomas for which evaluable T1-weighted images were available were isointense with the bladder wall. The lesions had a slightly higher signal intensity than the bladder wall in 15 of the patients (83%) and showed isointensity with the bladder wall in three patients (17%). A total of three patients (17%) had tiny hyperintense foci noted on T2-weighted images. All 16 of the inverted urothelial papillomas examined by DWI had very high signal intensity. All 13 of the lesions for which early phase images were obtained using dynamic contrast-enhanced MRI showed strong enhancement. When compared with early phase images, delayed phase images of the same 13 lesions showed that enhancement was stronger in two lesions (15%), similar in six lesions (46%), and weaker in five lesions (38%).

CONCLUSION

On MRI, the typical appearance of inverted urothelial papillomas of the bladder is a polypoid shape with a nonpapillary surface and a thin short stalk surrounded by urine. Cystic foci are also occasionally seen within the tumor.

A case of bladder-inverted papilloma after brachytherapy for prostate cancer

An 82-year-old male who presented with the chief complaint of gross hematuria and a history of prostate cancer treated with brachytherapy 6 years previously is described. Cystoscopy revealed multiple bladder tumors on the right posterior wall. A transurethral resection of the bladder tumor was performed and a pathological diagnosis of the inverted papilloma was made. To the best of our knowledge, this case is the first report of bladder-inverted papilloma after brachytherapy for prostate cancer.