Variants of urothelial carcinoma apart from those with glandular,squamous or neuroendocrine differentiation: key morphologic features,differential diagnoses and prognostic significance

Urothelial carcinoma of the bladder may exhibit divergent differentiation and can present a challenge to the reporting pathologist. A variety of different morphologic subtypes have been described, many of which are included in the 2004 World Health Organization Classification. Some of these may impact on prognosis and direct therapy accordingly. This article presents an overview of the variant histological types of urothelial carcinoma of the bladder, apart from glandular, squamous and neuroendocrine differentiation, with an emphasis on key morphological features and potential differential diagnoses.     

Molecular classification of urothelial carcinoma: global mRNA classification versus tumour‐cell phenotype classification

Global mRNA expression analysis is efficient for phenotypic profiling of tumours, and has been used to define molecular subtypes for almost every major tumour type. A key limitation is that most tumours are communities of both tumour and non‐tumour cells. This problem is particularly pertinent for analysis of advanced invasive tumours, which are known to induce major changes and responses in both the tumour and the surrounding tissue. To identify bladder cancer tumour‐cell phenotypes and compare classification by tumour‐cell phenotype with classification by global gene expression analysis, we analysed 307 advanced bladder cancers (cystectomized) both by genome gene expression analysis and by immunohistochemistry with antibodies for 28 proteins. According to systematic analysis of gene and protein expression data, focusing on key molecular processes, we describe five tumour‐cell phenotypes of advanced urothelial carcinoma: urothelial‐like, genomically unstable, basal/SCC ‐like, mesenchymal‐like, and small‐cell/neuroendocrine‐like. We provide molecular pathological definitions for each subtype. Tumours expressing urothelial differentiation factors show inconsistent and abnormal protein expression of terminal differentiation markers, suggesting pseudo‐differentiation. Cancers with different tumour‐cell phenotypes may co‐cluster (converge), and cases with identical tumour‐cell phenotypes may cluster apart (diverge), in global mRNA analyses. This divergence/convergence suggests that broad global commonalities related to the invasive process may exist between muscle‐invasive tumours regardless of specific tumour‐cell phenotype. Hence, there is a systematic disagreement in subtype classification determined by global mRNA profiling and by immunohistochemical profiling at the tumour‐cell level. We suggest that a combination of molecular pathology (tumour‐cell phenotype) and global mRNA profiling (context) is required for adequate subtype classification of muscle‐invasive bladder cancer. © 2017 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.     

Pathology of flat bladder lesions with emphasis on putative precursors

Flat bladder lesions comprise a spectrum of morphologic changes ranging from reactive atypia to carcinoma in situ (CIS). Differentiating these lesions is important because of differences in patient management and clinical outcome. The precise nature of precursor lesions of bladder cancer remains incompletely understood. Urothelial CIS is the most definitely characterized precursor lesion of high grade bladder cancer. Atypia of unknown significance (AUS) is somewhat controversial. For practical purposes, AUS and reactive urothelial changes should be considered a single entity, since neither lesion has established preneoplastic potential. Simple hyperplasia and papillary hyperplasia are recently identified putative preneoplastic lesions. More recent molecular data also support the precursor nature of intestinal metaplasia and keratinizing squamous metaplasia. In this review, we also discuss the utility of molecular ancillary studies in establishing premalignant lesions, diagnosis, and differential diagnosis of flat bladder lesions.     

Expression and function of SIRT6 in muscle invasive urothelial carcinoma of the bladder

SIRT6, a member of the class III histone deacetylase, has been shown to inhibit glycolysis and promote DNA double strand break repairs. Despite of its proposed tumor suppressor role, no significant differences in SIRT6 mRNA levels among normal bladder urothelium, non-muscle invasive, and muscle invasive urothelial carcinoma were noted in the two largest bladder cancer gene expression datasets available in Oncomine^TM. We therefore studied the expression and function of SIRT6 in muscle invasive urothelial carcinoma of the bladder. Immunohistochemistry studies of SIRT6 on radical cystectomy samples showed a dramatic decline of SIRT6 expression when bladder cancer progressed from T2 to T4. Functional study with bladder cancer cell lines confirmed its role in inhibiting glycolysis and cell proliferation. Reducing SIRT6 with siRNA, however, did not sensitize bladder cancer cells to drug induced DNA damage. The differential expression patterns of SIRT6 amongst different T stages of muscle invasive bladder cancers indicate less reliance on glycolysis when urothelial carcinoma invades deeper through the bladder and into the adjacent tissues.     

Comprehensive pathological assessment of histological subtypes,molecular subtypes based on immunohistochemistry,and tumor-associated immune cell status in muscle-invasive bladder cancer

Molecular assessments of muscle-invasive bladder cancer (MIBC) have yielded several molecular categorizations associated with basal and luminal subtypes or tumor-associated immune cell status (TAICs). However, the histological relationships among histological subtypes, molecular subtypes, and TAICs and their clinical implications remain unclear. Thus, we aimed to evaluate the histological associations among these factors and their clinicopathological outcomes. We retrospectively analyzed 106 patients with MIBC who underwent radical cystectomy. The histological subtypes and TAICs were evaluated with hematoxylin and eosin staining, while the basal and luminal molecular subtypes were determined by immunohistochemical expression of cytokeratin (CK) 5/6, CK14, CK20, GATA3 and uroplakin II. Urothelial carcinoma with squamous differentiation and the sarcomatoid variant were highly associated with the basal subtype (P < 0.001 and P = 0.04, respectively). Additionally, high TAICs were significantly correlated with the basal subtype (P < 0.001). Although there was no significant difference in the cancer-specific survival (CSS) rate between molecular subtypes (P = 0.295), TAICs significantly discriminated CSS rates (P < 0.001). Furthermore, the combination of molecular subtypes and TAICs significantly stratified cancer-specific mortality rates. In conclusion, a comprehensive pathological evaluation of histological subtypes, molecular subtypes, and TAICs is feasible and can influence the oncological outcome.     

Fascin stain as a potential marker of invasiveness in carcinomas of the urinary bladder: a retrospective study with biopsy and cytology correlation

The evaluation of invasion in urothelial carcinomas of the urinary bladder cannot be determined on cytology and can be particularly challenging in biopsy cases with limited sampling. Recent studies of bladder resection specimens suggest that fascin overexpression may be a marker of aggressive urothelial carcinomas and can help facilitate the assessment of invasion. In this study, we evaluated urine cytology and corresponding biopsy specimens with proven invasive urothelial carcinoma for fascin expression by immunohistochemistry. Thirty‐five patients diagnosed with positive urine cytology and biopsy‐proven invasive urothelial carcinoma between January 2003 and February 2009 were identified. We found increased fascin expression in 100% (35/35) of SurePathTM&!trade; urine cytology preparations as well as 100% (35/35) of corresponding biopsy cases with invasive urothelial carcinoma. On urine cytology, cytoplasmic fascin staining was moderate to intense in malignant tumor cell clusters and single cells and not observed in benign urothelial cells. Staining in biopsy cases was generally intense and cytoplasmic and present in both the invasive (100%) and noninvasive (31%) components of the lesion. These findings uphold the association of increased fascin expression in invasive urothelial carcinomas of the urinary bladder. We furthermore demonstrate that fascin staining can be performed successfully on SurePathTM&!trade; urine cytology preparations in which increased fascin expression correlates with invasion on biopsy. While not a definitive marker of invasion, as it is observed in in situ carcinoma, we conclude that the utilization of fascin immunohistochemistry on urine cytology might serve as a useful adjunct in predicting invasiveness in subsequent biopsies. Diagn. Cytopathol. 2010. © 2010 Wiley‐Liss, Inc.     

RIN1在人膀胱尿路上皮癌中的表达

目的研究RIN1在人膀胱尿路上皮癌中的表达。方法分别应用免疫蛋白印迹技术和实时定量PCR技术检测RIN1蛋白和RIN1 m RNA在人膀胱尿路上皮癌及癌旁组织中的表达。结果 Real-time PCR结果发现,在15对新鲜的膀胱尿路上皮癌及癌旁组织中,有12对的癌组织中RIN1表达高于癌旁组织。在膀胱尿路上皮癌组织中,RIN1的m RNA表达平均倍数为10.61±5.42,癌旁组织中,RIN1的m RNA平均倍数为4.31±1.77,P0.05。Western blot法结果认证了RIN1在膀胱尿路上皮癌组织中的表达是升高的。结论 RIN1在膀胱尿路上皮癌组织中的m RNA和蛋白的表达水平高于癌旁组织。     

Urothelial carcinoma of the urinary bladder with a component of acinar/tubular type differentiation simulating prostatic adenocarcinoma

We report a case of an 83-year-old man with a high-grade carcinoma of the urinary bladder who underwent cystoprostatectomy. The invasive carcinoma showed mixed, morphologically distinct patterns consisting of conventional high-grade urothelial carcinoma, glandular differentiation resembling enteric type adenocarcinoma, and acinar/tubular type differentiation, morphologically similar to Gleason grade 3 prostatic adenocarcinoma. Immunohistochemical studies revealed the acinar/tubular component of the tumor to be negative for prostate-specific antigen and prostatic acid phosphatase, but positive for cytokeratin 7, cytokeratin 20, high molecular weight cytokeratin (34 beta E12), and thrombomodulin, consistent with origin from the bladder rather than the prostate. Although bladder carcinomas composed of mixed morphologic patterns are not uncommon, to our knowledge, the presence of acinar/tubular type features simulating prostatic adenocarcinoma in such tumors has not been described elsewhere.     

Frequent genetic alterations in flat urothelial hyperplasias and concomitant papillary bladder cancer as detected by CGH,LOH, and FISH analyses

Flat urothelial hyperplasia, defined as markedly thickened urothelium without cytological atypia, is regarded in the new WHO classification as a urothelial lesion without malignant potential. Frequent deletions of chromosome 9 detected by fluorescence in situ hybridization (FISH) have been previously reported in flat urothelial hyperplasias found in patients with papillary bladder cancer. Using comparative genomic hybridization (CGH) and microsatellite analysis, these hyperplasias and concomitant papillary tumours of the same patients were screened for other genetic alterations to validate and extend the previous findings. Eleven flat hyperplasias detected by 5-ALA-induced fluorescence endoscopy and ten papillary urothelial carcinomas (pTaG1-G2) from ten patients were investigated. After microdissection, the DNA of the lesions was pre-amplified using whole genome amplification (I-PEP-PCR). Loss of heterozygosity (LOH) analyses were performed with five microsatellite markers at chromosomes 9p, 9q, and 17p. CGH was performed using standard protocols. In 6 of 11 hyperplasias and 7 of 10 papillary tumours, deletions at chromosome 9 were simultaneously shown by FISH, LOH, and CGH analyses. There was a good correlation between FISH, LOH, and CGH analyses, with identical results in 6 of 10 patients. In addition to deletions at chromosome 9, further genetic alterations were detected by CGH in 9 of 10 investigated hyperplasias, including changes frequently found in invasive papillary bladder cancer (loss of chromosomes 2q, 4, 8p, and 11p; gain of chromosome 17; and amplification at 11q12q13). There was considerable genetic heterogeneity between hyperplasias and papillary tumours, but a clonal relationship was suggested by LOH and/or CGH analyses in 5 of 10 cases. These data support the hypothesis that flat urothelial hyperplasias can display many genetic alterations commonly found in bladder cancer and could therefore be an early neoplastic lesion in the multistep development of invasive urothelial carcinoma.     

易混淆的膀胱活检小细胞性浸润性尿路上皮癌的诊断与鉴别诊断：附1例报告

目的：探讨膀胱活检中小细胞性浸润性尿路上皮癌的病理形态学特征以及与其它小细胞性病变的鉴别诊断。方法：对北京中医药大学东直门医院1例膀胱黏膜活检的病理及临床资料进行回顾性分析,并对相关国内外文献进行复习。结果：患者,男性,82岁,膀胱镜下见：在膀胱颈部10~12点可见黏膜突起如蕈状,蒂不明显。活检组织光镜下见：1)尿路上皮下小细胞肿瘤细胞呈弥漫性及巢状分布,间质增生;2)瘤细胞体积小,呈短梭形或淋巴细胞样,胞浆极少,局部瘤细胞胞浆宽广透明;3)核为圆形、椭圆形或梭形,核深染且结构不清,部分核不规则,可见双核、核重叠及多核瘤巨细胞,核仁不明显;4)未见核分裂象;5)局部组织可见挤压现象及局灶凝固性坏死;6)可见脉管浸润;7)局部异型增生的尿路上皮基底层处与固有膜内的小细胞性肿瘤成分有移行。免疫组织化学结果显示免疫表型CK少数细胞弱(+),其余标记均(?),病理诊断为：小细胞低分化癌。临床行经尿道膀胱肿瘤电切术,未送病理,数月后发现肠系膜多个转移瘤结节,瘤细胞形态与活检相似,局部瘤细胞核偏位,可见核仁及病理性核分裂象,免疫组化显示上皮性标记、p63及CD44V6均(+),神经内分泌标记(?),综合考虑最后病理诊断为：膀胱小细胞性浸润性尿路上皮癌伴肠壁转移。结论：膀胱小细胞性浸润性尿路上皮癌在膀胱镜活检标本中诊断难度较大,应重视其病理特点,鉴别诊断需结合临床和免疫组化特征综合评价,当二者不能提供有价值的帮助时,确诊还需以HE切片形态学特征为主,同时在报告中加以注明。膀胱镜活检标本病理诊断尿路上皮癌核分裂象应是有或无。     

Micropapillary variant of urothelial carcinoma of the urinary bladder; a clinicopathological and immunohistochemical study

AIMS: To investigate whether prognosis in micropapillary urothelial carcinoma is related to the proportion of the micropapillary component (MPC), and to identify the immunohistochemical features of MPC. METHODS AND RESULTS: This study presents a clinicopathological analysis of 20 patients with micropapillary urothelial carcinoma of the bladder with cystectomy specimens for evaluation. Tumours were stratified on the extent of MPC: focal, <10%; moderate, 10-50%; extensive, >50%; and this was correlated with tumour stage and prognosis. Sixteen males and four females were aged 56-81 years (mean 69 years). All cases had high-grade morphology in the micropapillary carcinoma and typical urothelial carcinoma. All cases with extensive MPC (n = 4) were of a high pathological stage (pT3 or pT4) and died of disease (DOD) or other causes. Eighty percent with moderate MPC (eight of 10 cases) were pT3 or pT4 and 50% DOD or are alive with disease. Eighty-four percent with focal MPC (five of six cases) were pT1 or pTa. In high-stage cases, the most invasive component was MPC. High-stage cases had an 85% risk of being advanced at presentation with micropapillary carcinoma. All pT2 or lower stage cases had micropapillary carcinoma on prior transurethral resections of bladder tumour (TURB). High-stage carcinomas had 30% and 54%, respectively, of surface MPC and urothelial carcinoma in situ, in comparison with 85% and 28% in lower stage carcinomas. Immunohistochemical staining was similarly positive in MPC and typical urothelial carcinoma with cytokeratin (CK)7, CK20, epithelial membrane antigen, carcinoembryonic antigen and cytokeratin 34betaE12. CA125 staining was seen only in MPC in 43% of cases. CONCLUSIONS: Micropapillary urothelial carcinoma is a high-grade carcinoma in which the prognosis is related to the proportion and location of the MPC. Cases with moderate or extensive MPC are at high risk of being advanced at presentation. Cases with <10% MPC and surface MPC have a high chance of detection at an early stage. The morphology and immunohistochemical profile of the MPC suggest that it is a form of glandular differentiation in urothelial carcinoma.     

The Paris System: achievement of a standardized diagnostic reporting system for urine cytology

Urinary tract cytology is a common diagnostic test used in the initial work up of bladder cancer. Since its inception as an utilizable diagnostic technique by Dr. Papanicolaou in 1945, urinary cytology has proven to be a cheap, easily obtained, and accurate method in the detection of high-grade urothelial carcinoma. Despite readily agreed upon features of high-grade urothelial carcinoma, a reproducible, universally accepted reporting method has not been attained. The Paris System for Reporting Urinary Cytology was developed to bring about a standardized reporting system with specific diagnostic categories and clear cytomorphologic criteria for the reliable diagnosis of high-grade urothelial carcinoma. This paper sets out to review the utility of urinary cytology, the current understanding of urothelial carcinoma, and the diagnostic categories of The Paris System. We finish with a review of the current literature regarding implementation of The Paris System.     

Transition between urothelial carcinoma in situ and non-invasive micropapillary carcinoma as a pivot connection between diverse morphologies of bladder carcinoma: a case report of urothelial carcinoma with villoglandular differentiation

Urothelial carcinoma has numerous histological variants, and these variants may coexist in a single case. Here, we present a case of a 70-year-old man with urothelial carcinoma of the bladder with a maximal diameter of 5 mm that involved micropapillary and plasmacytoid variants, with villoglandular differentiation. The presence of these variants was confirmed by pathological examination of a transurethral resection specimen, and high-grade urothelial carcinoma was found as a minor component. Although this bladder carcinoma was classified as pT1, cystoprostatectomy, urethrectomy, and lymphadenectomy were performed due to the presence of the micropapillary and plasmacytoid variants, which are known to be aggressive. Examination of a surgically resected specimen revealed no carcinoma. A transition between urothelial carcinoma in situ and non-invasive micropapillary carcinoma was found to be a pivot point connecting the diverse morphologies of this bladder carcinoma, from which there existed two pathways. One pathway was from urothelial carcinoma in situ to the plasmacytoid variant through invasive high-grade urothelial carcinoma, and the other was from non-invasive micropapillary carcinoma to urothelial carcinoma with villoglandular differentiation or to the micropapillary variant. This is the 16th reported case of urothelial carcinoma with villoglandular differentiation in the literature. As urothelial carcinoma with villoglandular differentiation is often associated with aggressive variants, as shown in our case, it should be reported whenever encountered in routine pathological practice.     

Urinary bladder biopsy with denuded mucosa: denuding cystitis-cytopathologic correlates

Denuding cystitis is often encountered in tissue biopsies of bladder mucosa performed by either cold-cup forceps or wire loop electrocautery to evaluate hematuria or to rule out recurrent urothelial carcinoma. Lack of urothelium in these biopsies is often a frustrating experience, leading to a nonspecific interpretation. In this study, 151 cases of denuding cystitis were retrieved from the surgical pathology files of The Johns Hopkins Hospital over a 4-year period (1996-1999). Patients under the age of 40 years and outside consultation material were excluded. Of the 151 cases of denuding cystitis, 48 patients were identified who had concurrent urinary cytologic studies. Of these patients, 35 were male (73%) and 13 were female (27%). Patient ages ranged from 43 to 85 years (mean, 67). Twenty-six of these 48 patients (54%) had at least one concurrently positive urinary cytology, which was histologically confirmed. All except three cases were high-grade urothelial carcinoma with the following histologic subtypes: flat carcinoma in situ (n = 11), noninvasive papillary (n = 9), and invasive urothelial carcinoma (n = 3). We conclude that urinary cytology is a sensitive modality that detects exfoliated carcinoma cells in patients with a histologic diagnosis of denuding cystitis. An inconclusive diagnosis of denuding cystitis on tissue might be related to biopsy method and technique, small sample size, or biopsy of cystoscopically abnormal urothelium that is denuded. A cytologic diagnosis of high-grade urothelial carcinoma in these cases leads to a timely clinical intervention for optimal patient management.     

High expression of Notch ligand Jagged2 is associated with the metastasis and recurrence in urothelial carcinoma of bladder

Background: The Notch signaling pathway is closely related with human organ development and tumorgenisis. Jagged2 is among the most popular topic in Notch studies currently. Recent studies found its vital role in tumor metastasis in breast cancer; however, its expression profile and its prognostic value in urothelial carcinoma of bladder have not been investigated. Methods: Immunohistochemistry was used to detect the expression of Jagged2 in 120 bladder urothelial carcinoma. Moreover, the expression of Jagged2 was analyzed by Western blot in 60 bladder urothelial carcinoma and 20 normal epithelial tissues. MTT assay and flow cytometry and transwell assay were used to examine the proliferative and invasive ability of bladder cancer cells with the treatment of GSIXX (the inhibitor of Jagged2). Prognostic value of Jagged2 expression and its correlation with tumor metastasis and recurrence were evaluated, and the proliferative and invasive ability and cell cycle process of the bladder cancer cells were detected as well. Results: There was a significantly higher Jagged2 expressions in bladder urothelial carcinoma and highly invasive bladder T24 cells than those in bladder normal tissues and the superficial bladder BIU-87 cells. Jagged2 expression was positively correlated with histological grade, p T stage, recurrence, and metastasis. With the increasing concentration of GSIXX, we found that not only the cell proliferation and invasion activity decreased significantly, but also the cell cycle was blocked at G₂/M stage. Conclusions: Jagged2 expression status was closely correlated with important histopathologic characteristics (grades and stages) and the recurrence and metastasis of bladder urothelial carcinomas. Furthermore, Jagged2 played an important function on the bladder cancer cells’ proliferation by regulating the cancer cell cycle from G₁/S to G₂/M and probably promoted the invasion and metastasis of bladder cancer.     

Non‐urothelial carcinomas of the bladder

Non‐urothelial carcinomas involving the bladder are uncommon and often diagnostically challenging. These carcinomas may show squamous, adenocarcinomatous or neuroendocrine features, with immunohistochemical stains aiding the diagnosis in only a subset of cases. The clinical history in non‐urothelial bladder carcinomas is important, given that the differential diagnosis often includes secondary involvement of the bladder by direct extension or metastasis from carcinomas at other sites. This paper will review non‐urothelial carcinomas in each of these three morphological categories, emphasising recent changes in diagnostic grouping and challenges in the histopathological diagnosis. Review of bladder cancers with squamous morphology will include discussion of conventional squamous cell carcinoma and verrucous carcinoma and their distinction from urothelial carcinoma with extensive squamous differentiation. Bladder carcinomas with adenocarcinomatous change will include primary bladder adenocarcinoma, urachal adenocarcinoma and tumours of Müllerian type. Finally, neuroendocrine neoplasms of the bladder, including well‐differentiated neuroendocrine tumour and neuroendocrine carcinomas, will be discussed. Associated surface findings, risk factors and prognostic features will be described.     

Ribonucleotide reductase M2 subunit is a novel diagnostic marker and a potential therapeutic target in bladder cancer

Morikawa T, Maeda D, Kume H, Homma Y & Fukayama M
(2010) Histopathology 57, 885–892 Ribonucleotide reductase M2 subunit is a novel diagnostic marker and a potential therapeutic target in bladder cancer Aims: To examine the immunohistochemical expression and function of ribonucleotide reductase M2 subunit (RRM2), a gemcitabine‐related molecule, in bladder cancer. Methods and results: One hundred and seventeen bladder specimens on a tissue microarray were immunostained for RRM2. Positive RRM2 staining was observed in none of 14 examples of non‐neoplastic urothelium, none of four low‐grade urothelial carcinoma (UC), 69 of 83 (83%) high‐grade UC, three of three (100%) squamous cell carcinoma and 12 of 13 (92%) lymph node metastasis of UC. RRM2 overexpression was associated significantly with muscularis propria invasion in UC patients who had undergone radical cystectomy (P = 0.005). Immunohistochemistry for RRM2 was then applied to small biopsy specimens of 15 cystitis with reactive atypia cases and 25 urothelial carcinoma in‐situ (CIS) cases. Positive RRM2 staining was found in one of 15 (6.7%) cystitis with reactive atypia cases and in 24 of 25 (96%) CIS cases. Finally, UM‐UC‐3 bladder cancer cells were transfected with RRM2 siRNAs and cell growth was evaluated. Knockdown of RRM2 protein markedly inhibited cell growth. Conclusions: We have shown frequent overexpression of RRM2 protein and its possible role in bladder cancer. Our results suggest that RRM2 is a novel diagnostic marker and a potential therapeutic target in bladder cancer.     

Primary multiple clear cell variant urothelial carcinomas of urinary bladder: a rare case report

Clear cell variant urothelial carcinoma of urinary bladder was very rare. There were only 6 report articles included by Pubmed and total 8 cases had been described till now. All of the past reports described single tumor of urinary bladder, but multiple carcinomas had not been reported. Here we reported a 65-years-old Chinese man who complained of intermittent gross hematuria and odynuria for more than 2 months in January 2013. Only one cauliflower-like tumor was detected approximately in the left wall of the urinary bladder with cystoscopy and the biopsy specimen was diagnosed as “urothelial carcinoma, high grade”. However, three tumors were found in anterior wall (×2) near neck of urinary bladder and posterior wall (×1) of the urinary bladder during transurethral resection of the bladder tumor. Typical urothelial carcinoma with partial clear cell appearance made it difficult to make a precise pathological diagnosis and immunohistochemical stain helped to diagnose the case as clear cell variant urothelial carcinoma, but not metastasis of the renal cell carcinoma. Finally, computerized tomographic scanning confirmed that there was no primary tumor in the kidney. The clinical and pathological characteristic had not been identified for the limited reports. More work should be done to know this kind of tumor well for guiding clinical therapy.     

Frequent FGFR3 mutations in urothelial papilloma

Activating point mutations in the FGFR3 gene occur frequently in low-grade and low-stage bladder carcinomas, whereas they are rare in high-grade carcinomas. This study investigates the incidence of FGFR3 mutations in 12 urothelial papillomas and 79 pTaG1 tumours which were regraded according to the 1998 WHO/ISUP classification system, resulting in 62 papillary urothelial neoplasms of low malignant potential (PUNs-LMP) and 17 low-grade papillary urothelial carcinomas (LG-PUCs). FGFR3 mutation analysis of 21 ovarian Brenner tumours was also performed. Seventy-seven cases were detected with a mutation in the FGFR3 gene. The mutations were exclusively found in bladder neoplasms. In urothelial papilloma, generally considered a benign lesion, 9/12 (75%) mutations were found. This report is the first to describe a genetic defect in urothelial papilloma. A comparable percentage of mutations was found in PUNs-LMP (85%) and LG-PUCs (88%). No mutations were found in matched normal DNA from bladder tumour patients. The mean follow-up was 5.78 years (range 0.21-17.60 years). Five patients developed high-grade papillary urothelial carcinoma from 2.5 to 12 years after first diagnosis. Two patients died of bladder cancer. The mean number of recurrences (recurrence rate) per year was 0.03, 0.21, and 0.46, respectively, for papilloma, PUN-LMP, and LG-PUC. Urothelial papilloma is a rare lesion with a benign natural behaviour compared with PUN-LMP and LG-PUC of the bladder, but from a molecular perspective, papillomas should be classified together with all well-differentiated urothelial neoplasms.     

Pathological and molecular aspects of urothelial carcinomas

Bladder cancer diagnosis still relies mainly on morphologic/classical pathology, which gives quickly the most important parameters needed, such as stage, grade and the presence of bad prognosticators (lymphovascular invasion, carcinoma in situ, variant histology). During the last 8 years, much progress has been made from a molecular point of view. Much new evidence has allowed us to gain deeper insight into not only the development of bladder cancer but also its complexity, and is leading us to potential new ways of treatment. The aim in the long term is to put both systems – pathology and molecular exploration – together, to allow the perfect individual treatment of each patient. This review attempts to find the overlaps between the two systems and to apply the molecular findings to a pathologist's daily practice.