Clinical Implications of the 2004 WHO Histological Classification on Non-Invasive Tumours of the Urinary Bladder

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1 eau-ebu update series 4 (2006) available at journal homepage: Clinical Implications of the 2004 WHO Histological Classification on Non-Invasive Tumours of the Urinary Bladder Thomas Hofmann a, *, Ruth Knüchel-Clarke b, Arndt Hartmann c, Robert Stöhr d, Derya Tilki a, Michael Seitz a, Alexander Karl a, Christian Stief a, Dirk Zaak a a Department of Urology, Klinikum Grosshadern, Ludwig-Maximilians University, Munich, Germany b Institute of Pathology, RWTH Aachen, Aachen, Germany c Institute of Pathology, University of Regensburg, Regensburg, Germany d Department of Urology, University of Regensburg, Regensburg, Germany Article info Keywords: Non-invasive urothelial tumours WHO classification Recurrence rate Progression rate Abstract The 1973 World Health Organization (WHO) typing system for bladder tumours is still widely used despite the lack of detailed histhopathological criteria. The more recent 2004 WHO blue book on pathology and genetics of tumours of the urinary system and male genital aimed to improve the recognition of subgroups by setting out well defined histomorphological criteria and dividing tumours with different biological characteristics that correlate with different clinical outcomes. However, the prognostic value of the 2004 WHO classification on non-invasive urothelial lesions is under discussion and there are questions concerning the clinical relevance of this system. This review is derived from data of available clinical trials to test the validity of the 2004 WHO classification for non-invasive bladder lesions by comparing tumour recurrence, progression and survival rates between different entities. Furthermore, we tried to evaluate the prognostic use of genetic alterations and biological markers with regard to impact on clinical management decisions. In our view, the 2004 WHO classification system does identify clinically and biologically distinct groups within the spectrum of non-invasive urothelial tumours. However, until the new classification is fully validated, and those working in the field have become familiar with it, the 1973 WHO typing system for bladder tumours is best mentioned additionally in the histopathological report. # 2006 European Association of Urology. Published by Elsevier B.V. All rights reserved. * Corresponding author. Urologische Klinik und Poliklinik, Klinikum der Universitaet Grosshadern, Ludwig-Maximilians-Universitaet Muenchen, Marchioninistr. 15, Muenchen, Germany. Tel ; Fax: address: Thomas.Hofmann@med.uni-muenchen.de (T. Hofmann) /$ see front matter # 2006 European Association of Urology. Published by Elsevier B.V. All rights reserved. doi: /j.eeus

2 84 eau-ebu update series 4 (2006) Introduction For many years classification systems of urothelial tumours of the bladder have aimed to define two clinically relevant groups: non-invasive low-grade tumours with high risk of recurrence but very low progression rates and high-grade tumours with a considerable risk of progression to invasive disease. The imprecise definition of grade 2 tumours in the 1973 World Health Organization (WHO) typing system for bladder tumours [1] has resulted in an accumulation of cases classed as grade 2 or grade 1 2 and grade 2 3, which has led to large and heterogenous cohorts of patients. As a result the reproducibility and prognostic relevance of the 1973 WHO classification for bladder tumours was discussed controversely [2]. Furthermore, the definition of flat non-invasive urothelial lesions was vague and the diagnostic reproducibility of urothelial dysplasia and carcinoma in situ (CIS) was low [2]. In 1998 the WHO and the International Society of Urologic Pathologists (ISUP) established a new histological grading to create a universally acceptable classification system for bladder neoplasms that could be used effectively by pathologists, urologists and oncologists [3]. In an attempt to include advances in the molecular evaluation of non-invasive urothelial tumours the 1998 WHO/ ISUP classification was slightly modified in the 2004 WHO classification for non-invasive urothelial tumours [4]. The recent classification is intended to achieve a uniform diagnosis of urothelial tumours by means of an exact definition of subgroups, stratified according to risk profiles and prognostic relevance (Table 1). This review aims to evaluate the 2004 WHO classification in as far as it concerns noninvasive bladder lesions with regard to its impact on clinical management. Our further interest lies in, whether a correlation with immunohistochemical or molecular markers allows for a refinement in the management strategies for specific subgroups. 2. Flat non-invasive urothelial lesions 2.1. Urothelial hyperplasia (UH) Biological relevance When diagnosed without a concomitant urothelial tumour UH is regarded as an entity with no evidence suggesting that it has any premalignant potential according to the 2004 WHO classification (Table 1) [4]. Despite this rather harmless description two recent studies [5,6] found identical genetic alterations in both flat and papillary UH and subsequent urothelial carcinoma. Obermann et al. [7] confirmed the findings by demonstrating, that UHs diagnosed in patients with bladder cancer had the same frequency of chromosome 9 alterations as corresponding tumours and were clonally related to Table 1 Histopathological definitions for non-invasive urothelial lesions according to the 2004 WHO classification for tumours of the urinary system [4] 2004 WHO definition [4] Flat lesions Urothelial hyperplasia Urothelial hyperplasia is defined as markedly thickened mucosa without cytological atypia. Urothelial atypia: - reactive atypia Reactive atypia occurs in acutely or chronically inflamed urothelium and has nuclear changes clearly ascribable to a reactive/regenerative process. - atypia of unknown significance Atypia of unknown significance is not a diagnostic entity, but a descriptive category for cases with inflammation in which the severity of atypia appears out of proportion to the extent of inflammation such that dysplasia cannot be confidently excluded. Urothelial dysplasia Dysplasia (low grade intraurothelial neoplasia) has appreciable cytologic and architectural changes felt to be preneoplastic but which fall short of carcinoma in situ. Urothelial carcinoma in situ A non-papillary, i.e. flat, lesion in which the surface epithelium contains cells that are cytologically malignant. Papillary lesions Urothelial papilloma Inverted papilloma Papillary urothelial neoplasm of low malignant potential (PUNLMP) Non-invasive papillary urothelial carcinoma, low grade (LGPUC) Non-invasive papillary urothelial carcinoma, high grade (HGPUC) Exophytic urothelial papilloma is composed of a delicate fibrovascular core covered by urothelium indistuingishable from that of the normal urothelium. Benign urothelial tumour that has an inverted growth pattern with normal to minimal cytologic atypia of the neoplastic cells. PUNLMP is a papillary urothelial tumour which resembles the exophytic urothelial papilloma, but shows increased cellular proliferation exceeding the thickness of normal urothelium. A neoplasm of urothelium lining papillary fronds which shows an orderly appearance, but easily recognizable variations in architecture and cytologic features. A neoplasm of urothelium lining papillary fronds which shows a predominant pattern of disorder with moderate-to-marked architectural and cytologic atypia.

3 eau-ebu update series 4 (2006) these lesions. Additional genomic alterations were demonstrated by comparative genomic hybridization (CGH) in a subset of UHs [7]. In contrast, both molecular and immunohistochemical analysis of papillary UHs did not show deletions or overexpression of p53 or significant expression of the proliferative marker Ki-67 [8]. Taken together, data from clinicopathological studies found that UH was closely associated with a history of urothelial carcinoma [9] and the above cited studies on genetic alterations indicate that some of these hyperplastic lesions might have the potential to progress to urothelial malignancies. Current evidence on the neoplastic potential of UH is, however, still inconclusive [10] Clinical implications Recent studies [5,7,11] have shown that photodynamic diagnosis through 5-aminolaevulinic acid induced fluorescence enables the detection and excision of bladder lesions, including UH, which might have been missed in white light cystoscopy. If UH is diagnosed de novo its neoplastic potential is controversial and no recommendations for clinical follow-up can be offered based on reliable data of the natural history of this lesion. In our opinion patients with de novo UH should be recommended cystoscopic follow-up with photodynamic diagnosis in 3- to 6-monthly intervals as the role of UH in the multistep process of urothelial tumorigenesis is still not clear. If papillary UH is found in a patient with a history of bladder cancer, this finding is often associated with recurrent tumour growth and close follow-up is recommended [9,12] Urothelial atypia (reactive atypia, atypia of unknown significance) In contrast to the 1973 WHO classification, which did not define the term atypia, the 1998 WHO/ISUP and 2004 WHO classification recognized two types of atypia (Tables 1 and 2). Table 2 Changes in terminology of non-invasive flat urothelial lesions according to the 1973 WHO and 2004 classification for bladder tumours 1973 WHO histological typing for urinary bladder tumours [1] Papillary (polypoid) cystitis Unstable mucosa Carcinoma in situ 2004 WHO classification for tumours of the urinary system [4] Urothelial hyperplasia Urothelial atypia - reactive atypia - atypia of unknown significance Urothelial dysplasia Urothelial carcinoma in situ Reactive atypia (RA) biological relevance A history of stones, infection or instrumentation is often present in patients with RA. Whereas in the 1998 WHO/ISUP consensus classification RA is considered not to be neoplastic [3], there is no statement regarding the benign character of this lesion in the 2004 WHO classification. Immunohistochemical studies on the expression of cytokeratin 20 (CK20), cytokeratin clone 34betaE12, MIB-1 and E-cadherin were not able to demonstrate significantly different expression patterns of the above markers in RA and normal urothelium [13,14]. Investigation of cell proliferation using Ki-67 produced controversial results with 28% of cases with RA showing increased expression of Ki-67, particularly when associated with intense inflammation [14]. Furthermore, p53-reactivity patterns were found to be identical in RA and normal urothelium [15]. No progression of RA to urothelial carcinoma or development of urothelial dysplasia (UD) has been diagnosed in a cohort of 25 patients with a mean follow up of 3.9 years [16] Clinical implications According to the above mentioned findings RA should be included among benign urothelial abnormalities without a need for regular cystoscopic follow up. Therapy should aim to treat underlying inflammatory conditions or lithiasis Atypia of unknown significance (AUS) biological relevance It is important to realize that AUS is not a diagnostic entity but merely a descriptive term used in diagnostically difficult cases. A recent study [14] evaluated the efficacy of CK20 and Ki-67 in further differentiating AUS from dysplastic urothelium. Fortyseven percent of the patients initially diagnosed as AUS demonstrated abnormal CK20 and increased Ki-67 expression suggestive of UD, 29% were negative with both markers suggestive of RA, and the remaining 24% of cases could not be resolved. Further follow-up of 10 cases revealed carcinoma in situ (CIS) in 7 cases and RA was confirmed in 3 patients. In contrast Cheng et al. [16] found that none of the 35 patients with AUS included in their study developed urothelial carcinoma during a mean follow up of 3.9 years. In view of these findings, evidence supporting a premalignant nature in AUS is controversial Clinical implications The message conveyed to the urologist by use of the term AUS is, that patients diagnosed with this

4 86 eau-ebu update series 4 (2006) lesion should be followed-up after inflammatory changes have subsided in order to further specify the underlying urothelial abnormality Urothelial dysplasia low grade intraurothelial neoplasia (UD) Biological relevance The incidence of UD in patients with non-invasive bladder cancer varies from 22% to 86% and approaches 100% in patients with muscle-invasive carcinoma [10]. The 2004 WHO classification system simplified the diagnosis of UD by elimination of the poorly reproducible grading system for dysplasias used in previous classifications. UD is now diagnosed in all lesions with clearly visible atypia which do not fulfill the diagnostic criteria of CIS. The presence of UD either adjacent to a concominant urothelial carcinoma or as primary UD, has been positively correlated to the risk of tumour recurrence and progression in the past [17,18]. In two recent series [16,19] progression to either CIS or muscle invasive disease was found in 19% and 15% of patients with primary UD during a mean follow-up of 8.2 vs. 3.9 years. The interval from initial diagnosis of UD to progression to muscle invasive cancer was 0.7 to 10.0 years and for progression to carcinoma in situ the corresponding time range was 0.6 to 3.0 years. Furthermore, the study by Cheng et al. [19] revealed that urothelial carcinomas did not arise in the region of UD in 6 of 7 cases. These results indicate that UD appears to be a marker of a field defect with elevated cancer risk. Furthermore, molecular studies could demonstrate that approximately 60% of UD showed deletions and mutations of p53 and chromosome 9 deletions, arguing that a proportion of these lesions could be precursors of CIS and invasive bladder cancer [20] Clinical implications Diagnosis of UD marks an urothelium with genomic damage and instability and a possibility of disease progression. Close follow-up with regular cytology and cystoscopy in patients diagnosed with this entity is recommended to document the course of UD and to detect early cases of carcinoma [15]. Although, in patients with both UD and bladder cancer therapy is directed towards the carcinoma, current literature provides no clear therapeutical directives for patients with primary UD. In our view, no treatment is indicated in primary UD provided that patients are under close follow-up with cystoscopy and cytology at 3- to 6-monthly intervals Urothelial carcinoma in situ (CIS) By comparison with the 1973 WHO classification the diagnostic criteria of CIS in the 1998 WHO/ISUP classification were refined to emphasize that cytological changes such as nucleomegaly, hyperchromasia, pleomorphism and mitotic activity in the mid and upper urothelium were key markers for the diagnosis of CIS. Finding these changes over the entire thickness of the urothelium is no longer required for the diagnosis of CIS. Given these modifications, CIS according to the 1998 WHO/ISUP and 2004 WHO classification (Table 1) encompasses lesions which in the past were designated as severe dysplasia or marked atypia [3] Risk of recurrence and progression Primary CIS accounts for less than 1 3% of urothelial carcinomas. Concurrent CIS can be found in 45 65% of muscle-invasive and in 5 19% of non-invasive urothelial tumours [4,21]. A recent study [22] on patients with primary CIS and concurrent CIS associated with non-invasive cancer reported a progression free rate of 63% and a cancer specific survival rate of 79% at 10 years. Furthermore, no outcome difference was found between patients with isolated CIS and those with coexisting noninvasive tumours. In contrast, patients with muscleinvasive cancer and concurrent CIS had a signifantly higher risk of disease progression (59% vs. 28%) and death (45% vs. 7%) than patients with primary CIS [23]. Concurrent results recently published by Hassan et al. [24], found a significantly higher rate of metastatic disease (22.7% vs. 3.6%) in patients with a previous complete resection of muscleinvasive bladder cancer and concurrent CIS when compared with primary CIS in cystectomy specimens. However, this discrepancy may be more a consequence of the muscle-invasive cancer than a proof for the aggressiveness of concurrent CIS. From a clinical perspective, extent of disease (focal/ multifocal), coexistent invasive carcinoma and recurrence were the principal determinants of clinical outcome in recent studies on CIS [10,25]. On a molecular level the combined expression of markers p53/p21, the loss of E-cadherin expression and the loss of chromosome 9 and 9p21 were associated with progression and cancer specific survival in CIS patients [25]. Furthermore, recent studies found frequent p53 mutations, lack of fibroblast-growth-factor-3-receptor (FGFR3) mutations and specific global gene expression alterations in CIS, suggesting that CIS is a precursor of invasive bladder cancer [20,26,27]. However, for progression specifically in patients with CIS the clinical value of

5 eau-ebu update series 4 (2006) markers, like oncogenes, cell cycle regulator genes, proliferation and neovascularisation markers remains to be determined [25] Clinical implications Although the refined histopathological definition for CIS includes a minority of cases that were previously diagnosed as severe dysplasia and atypia [3] this refinement is not expected to have a significant impact on the clinical outcome of this entity and we know of no studies that have investigated this topic. According to recent guidelines on the diagnosis and treatment of CIS [21] urine cytology has a sensitivity and specificity of over 90% in CIS. Fluorescence cystoscopy has proven superior sensitivity over white light endoscopy and is recommended for diagnosis and follow-up of CIS [11,21]. Where CIS is found as a concurrent lesion associated with muscle-invasive bladder cancer therapy is directed towards the invasive carcinoma. While, in cases of primary CIS or CIS in presence of Ta/T1 urothelial carcinoma no consensus exists regarding the recommended therapy (topical BCG vs. early cystectomy). Patients with CIS, even complete responders after topical BCG, should be monitored lifelong, because of the risk of recurrence and progression [21]. 3. Papillary non-invasive urothelial lesions 3.1. Urothelial papilloma (UP) Biological relevance The 1973 WHO definition of UP and the 2004 WHO classification differ mainly in that the number of cell layers need no longer be counted in the recent classification as was previously required (Table 3). According to Oosterhuis et al. [28] some of the initially graded G1-tumours were reclassified as UP when using the less stringent 2004 WHO criteria and this accounted for a rise of the total number of papillomas diagnosed in this study. The biological potential of UP is inconclusive as there is only a limited number of studies dealing with this issue while using the recent WHO or WHO/ ISUP classification: Harnden et al. [29], Desai et al. [30] and Samaratunga et al. [31] found neither recurrence nor progression of UP during a median follow-up of months, whereas publications by Table 3 Changes in terminology and histological features of noninvasive papillary urothelial tumours according to the 1973 WHO and 2004 WHO classifications for bladder tumours 1973 WHO histological typing of urinary bladder tumours [1] Transitional cell papilloma - Papillary tumour with delicate fibrovascular stroma covered by regular transitional epithelium not more than 6 layers thick - Tumour may recurr and behave in a malignant manner Transitional cell papilloma, inverted type Grade 1 transitional cell carcinoma Grade 2 transitional cell carcinoma Grade 3 transitional cell carcinoma 2004 WHO classification for tumours of the urinary system [4] Urothelial papilloma Inverted papilloma Papillary urothelial neoplasm of low malignant potential (PUNLMP) Non-invasive papillary urothelial carcinoma, low grade (LGPUC) Non-invasive papillary urothelial carcinoma, high grade (HGPUC) - Characteristics of a transitional cell papilloma but with an endophytic growth pattern...tumours that have the least degree of cellular anaplasia compatible with a diagnosis of malignancy......grade 2 lies in between....tumours with the most severe degrees of cellular anaplasia......composed of a delicate fibrovascular core covered by urothelium indistuinguishable from that of normal urothelium. Benign urothelial tumour that has an inverted growth pattern with normal to minimal cytologic atypia of the neoplastic cells. - Discrete papillary growth lined by multilayered urothelium exceeding the thickness of normal urothelium - Umbrella cell layer often preserved - Polarity normal, nuclei slightly enlarged, minimal to absent cytological atypia - Papillae often branching with minimal fusion - Recognizable variations in nuclear polarity, size, shape and chromatin distribution - Mitoses infrequent but may occur on any level - Papillae frequently fused and branching - Marked variations in nuclear polarity, size, shape and chromatin pattern - Mitoses are frequent and at any level

6 88 eau-ebu update series 4 (2006) Cheng et al. [32], McKenney et al. [33] and Magi- Galuzzi et al. [34] reported recurrent tumour growth in % and progression in % during a mean follow-up of up to 9.8 years. Patients with progression developed non-invasive tumours and none demonstrated an invasive carcinoma. Immunohistochemical studies on cell differentiation and proliferative activity examining the expression of CK20, CD44, p53 and Ki-67 in UP [8,13,29] could not distinguish normal urothelium from UP using these markers. Mutations of FGFR3 which are among the earliest events in urothelial carcinogenesis were found in low-grade papillary urothelial tumours in 85 88% and could also be detected in 75% of the investigated UPs [2,35]. The results of the latter studies might serve as an explanation as to why there is progression of UPs in rare cases. However, this has to be confirmed by further studies Clinical implications According to the definition of the 2004 WHO classification UP is a heterogenous neoplasm with different risk patterns of recurrence and progression. The results of the above quoted immunohistochemical and molecular studies favour the assumption that UP is the most highly differentiated entity in a spectrum of genetically stable, well differentiated papillary urothelial neoplasms. Recurrences of UPs were diagnosed from 4 months to >3 years after initial diagnosis and progression was reported from 15 months to >5 years in recent studies [32 34]. Accordingly, we recommend a follow-up for patients with UP by cystoscopy in yearly intervals for a period of >5 years. As UP rarely progressed to low grade carcinoma and progression to high grade tumours has only been reported anecdotally, urine cytology with its low sensitivity to low grade lesions appears not to be an adequate follow-up investigation if used exclusively Inverted papilloma (IP) Biological relevance As for UP (3.1) a maximum of six cell layers is no longer a restrictive histopathological criterion for the diagnosis of IP according to the recent WHO classification (Tables 1 and 3). The diagnosis of IP was associated with urothelial carcinoma occurring either simultaneously or subsequently in the past [36]. Recently, however studies comparing ploidy, MIB-1 proliferative activity, p53-, CK20- and Ki-67- expression in IP with and without cellular atypia and in IP of patients with and without a history of urothelial carcinoma could not detect any significant differences in IPs in any of the investigated groups [37,38]. Furthermore, molecular studies investigating IP showed neither FGFR3 mutations nor chromosome 9 deletions or other molecular alterations frequently found in papillary bladder cancer, favouring a benign nature of IP (pers. comm., unpubl. data, A. Hartmann, Univ. of Regensburg, Regensburg, Germany). Follow-up data on patients with IP demonstrated no recurrences [36,38] Clinical implications Reviewing these findings, we consider the biological behaviour of IP to be benign, providing there is no doubt about the histological diagnosis [36,38]. Papillary urothelial carcinomas with inverted growth pattern as well as invasive urothelial carcinoma have to be excluded in these patients [15]. Frequent and long-term follow-up after complete resection does not seem necessary in our opinion. However, if the resection of a lesion was incomplete, TUR should be repeated as residual tissue might harbour a malignant neoplasm and in those cases where histological features of possible malignant transformation exist, 3- to 6-monthly endoscopic investigations should be performed in our opinion Papillary urothelial neoplasm of low malignant potential (PUNLMP) Risk of recurrence and progression The term PUNLMP was introduced in the 1998 WHO/ISUP classification in recognition of the low probability of recurrence and a negligible risk of progression in a proportion of well differentiated, non-invasive, papillary tumours. Furthermore, the introduction of this new term aimed not to label patients diagnosed with this lesion with the term cancer. It is inaccurate merely to equate the 1973 WHO TaG1 urothelial bladder tumours with PUNLMP lesions (Tables 1 and 3). Recent publications [31,39,40] reported that after histopathological regrading using the 1998 WHO/ISUP or 1999 WHO classification 19% 44.8% of PUNLMPs were originally diagnosed as TaG1-2 or G2 tumours according to the 1973 WHO classification. With a mean percentage of recurrences of 37.5% and stage progression rate and tumour related mortality in approximately 3.3% and 1.3% in 11 available, mostly retrospective studies, PUNLMP lesions demonstrated a low malignant potential (Table 5). Outcome of TaG1 carcinomas (graded according to the 1973 WHO classification) showed a comparable percentage of tumour recurrences (15 55%) and tumour progression (0 5%) [41,42].

7 eau-ebu update series 4 (2006) Table 4 Correlation among the 1973 WHO grading and the recent WHO/ISUP and WHO classification systems for papillary bladder tumours WHO 1973 classification [1] WHO/ISUP 1998 classification [3] WHO 1999 classification [54] WHO 2004 classification [4] Transitional cell papilloma Urothelial papilloma Urothelial papilloma Urothelial papilloma Transitional cell papilloma, Inverted urothelial papilloma Inverted urothelial papilloma Inverted papilloma inverted type PUNLMP PUNLMP PUNLMP LGPUC WHO 1 (low grade carcinoma) LGPUC HGPUC WHO 2 (high grade carcinoma)/who 3 (high grade carcinoma) HGPUC TCC: transitional cell carcinoma; PUNLMP: papillary urothelial neoplasm of low malignant potential; LGPUC: papillary urothelial carcinoma, low grade; HGPUC: papillary urothelial carcinoma, high grade. In our opinion, further studies are needed to ascertain whether the introduction of PUNLMP has added clinically relevant prognostic value. The decisive question with regard to clinical follow-up is, which patient with PUNLMP will recur and progress? In a recent study 68% of patients with PUNLMP who were tumour free at the first follow-up cystoscopy remained tumour free during a followup period of at least 5 years [43]. Immunohistochemical studies on the expression of CK20, CD 44 and 34betaE12 as sensitive markers of urothelial differentiation reported a strong correlation of non-recurrent disease with a normal expression pattern of these markers in PUNLMPs and low grade papillary urothelial carcinomas (LGPUC) [29,30,44]. Further studies evaluated mitotic count and MIB-1 either alone or in association with the expression of p53, c-erbb-2 and bcl-2-oncogenes in predicting recurrence of PUNLMPs and LGPUCs [8,13,45]. In multivariate analysis, only MIB-1 immunopositivity, as a marker of proliferative activity retained prognostic significance [45]. The limitations of the above quoted studies were, that markers were evaluated by a variety of assays, interpreted according to variable criteria and studies included only limited numbers of patients. However, the above quoted studies came to the conclusion that p53 expression is uncommon in PUNLMP, whereas proliferative activity is increased in PUNLMP as compared with benign urothelium Clinical implications On the basis of the above quoted studies on immunohistochemical and molecular markers it is not possible to reliably divide up patients with PUNLMP into categories with a clearly different prognosis. According to the recent European Association of Urology (EAU) guidelines the number of tumours present at diagnosis is the most important prognostic factor for recurrence, followed by the recurrence rate in the previous period and size and grade of tumour [46]. Immediate chemo-instillation after TURB is recommended as it can reduce early recurrences [47]. According to Holmäng et al. [43] we recommend a follow-up cystoscopy 3-4 months after the initial diagnosis of PUNLMP and in case of a negative finding the next cystoscopy might be performed 9 months later and then yearly up to 5 years. In case of a recurrence at first follow-up we would suggest a follow-up schedule as recommended by the recent EAU-guidelines for low-risk tumours [46] Non-invasive papillary urothelial carcinoma, low-grade (LGPUC) Risk of recurrence and progression Although the majority of LGPUCs in recent studies were originally considered to be G2 carcinomas according to the 1973 classification, 3.5 to 39.0% of LGPUCs were initially graded as G1 carcinomas [28,31,48]. This demonstrates that there is no simple one-to-one correlation between LGPUC and G2 tumours as defined by the 1973 WHO classification (Table 4). In a multicentre study from Sweden [39,48] recurrences in 71% of patients with LGPUC compared with recurrences in 35% for PUNLMP lesions ( p < 0.001) were found after at least 5 years of followup (Table 5). Further publications with a mean

8 90 eau-ebu update series 4 (2006) Table 5 Recurrence, progesssion and mortality in PUNLMP Study No. of cases % Tumour recurrence % Stage progression % Tumour related mortality Mean follow-up Oosterhuis et al. [28] mo Cheng et al. [55] yr Holmäng et al. [39,48] >5 yr b Alvarez Kindelan et al. a [56] mo Fuji et al. [57] yr Ramos et al. [49] n.a. n.a mo Samartunga et al. [31] 29 n.a. (0.025 rec./yr) 8 c n.a mo Alsheikh et al. [44] n.a. n.a. n.a. Pich et al. [45] n.a. n.a mo Campbell et al. [40] n.a. 10 yr b Desai et al. [30] yr Mean percentage n.a.: not available. a Available only as an abstract and the definition of progression is not clear. b No mean follow-up period available. c 90 months actuarial risk of progression. follow-up of at least 5 years for LGPUC reported similar recurrence rates as from 64.1 to 75.0% and found stage progression in 3.6 to 10.5% [30,40,45,49]. On the other hand, Oosterhuis et al. [28] presented 30.5% recurrences in 141 LGPUC patients within a mean follow-up of 79 months. However, unlike the other quoted studies Oosterhuis et al. did not include a count of small papillary lesions which were coagulated at cystoscopy without histological confirmation and those tumours which were found at the first follow-up cystoscopy as recurrence. In the search for predictive information on biological behaviour several studies (see also 3.3) demonstrated that rapid tumour cell proliferation as measured by mitotic index, PCNA-labelling and Ki-67 labelling is associated with an increased risk of recurrence in low-grade tumours [8,45]. Other molecular markers that have been proposed as possible predictors of tumour recurrence in non-invasive papillary low grade tumours include overexpression of proline-directed protein kinase F, p14arf promoter hypermethylation, clusterin overexpresion, expression of the imprinted H19 gene and reduced expression of E-cadherin [4]. Data on the prognostic importance of biological markers in non-invasive low-grade carcinomas are scarce because of the rare progression of this entity. Two recent studies using cdna microarrays detected gene sets which could predict disease progression [26,50]. However, these data have to be validated in further studies. The final stage progression of non-invasive urothelial carcinomas seems to require another large series of genetic alterations, whose exact sequence has not yet been elucidated [2,51]. Currently, genetic differences and specific molecular markers hold out the promise of further future differentiation of risk groups in low-grade carcinoma, but are not as yet validated for routine clinical use. Table 6 Recurrence, progression and mortality in LGPUC Study No. of cases %Tumour recurrence % Stage progression % Tumour related mortality Mean follow-up Holmäng et al. [39,48] n.a. >5 yr a Oosterhuis et al. [28] mo Ramos et al. [49] n.a. n.a mo Samartunga et al. [31] 73 n.a. (0.045 rec./yr) 13 b n.a mo Pich et al. [45] n.a. n.a mo Desai et al. [30] yr Alsheikh et al. [44] n.a. n.a. n.a. Campbell et al. [40] n.a. 10 yr a Mean percentage n.a.: not available. a No mean follow-up period available. b 90 months actuarial risk of progression.

9 eau-ebu update series 4 (2006) Clinical implications The data shown in Tables 5 and 6 demonstrate a negligible risk of progression for PUNLMP compared with the still low but increased progression rate seen in LGPUC lesions. As for the high percentage of recurrences in LGPUC, immediate chemoinstillation after TURB should be encouraged as this can reduce early recurrent tumour growth (for prognostic factors for recurrence see 3.3.2) [47]. If there is recurrence, we recommend a 4 8 week course of bladder chemo-instillation. Follow-up cystoscopies are recommended according to the EAU-guidelines for intermediate risk bladder tumours [46] Non-invasive papillary urothelial carcinoma, high grade (HGPUC) The endoscopic appearance of HGPUC lesions can differ significantly from LGPUC and PUNLMP as nodular and solid forms of HGPUCs as also papillary growth patterns have been discerned [4] Risk of recurrence and progression After regrading all G3-lesions as classified according to the 1973 WHO typing system were categorized as HGPUC in accordance with the 1998 WHO/ISUP and 1999 WHO classification in recent studies [28,31]. These studies also showed that 15.4 to 36.0% of all neoplasms initially graded as G2-lesions were reclassified as HGPUC. This made HGPUC into a more frequently diagnosed and more heterogenous group than that of the former G3-tumours. When compared with tumour recurrence in 66.7% and 73% of patients as published by Campbell et al. and Holmäng et al. [39,40], Oosterhuis et al. [28] noted recurrent tumour growth in patients with HGPUC in only 40% of patients and reported a low percentage of tumour progression of 4.4% (Table 7). These contrasting results appear to be due to two facts: firstly, Oosterhuis et al. [28] chose a different study design in that histologically non-proven recurrences and recurrent lesions found at first check-cystoscopy were neglected in their study. Secondly, only one patient in the HGPUC cohort studied by them was initially graded G 3, while all the other patients were grade 2. Consequently, no significant difference could be demonstrated for HGPUC and LGPUC with respect to recurrence-free and progression-free survival in the latter study. By contrast, in a study by Holmäng et al. [39] disease progression was significantly different between patients with LGPUC and HGPUC ( p < ). In a review of only limited number of available studies (Table 7), recurrent tumour growth in 40 73% and stage progression in approximately a quarter of all patients with HGPUCs (maximum percentage of tumour progression: 51.7%) highlight aggressive biological behaviour. However, the transversion of a proportion of initially graded G2-lesions into HGPUCs seemed to have slightly reduced the overall frequency of tumour progression and recurrence for this entity as compared with the former TaG3- cohort, graded according to the 1973 WHO typing system, which had an 80% likelihood of recurrence at 3 years and tumour progression in 39.2% [52,53]. Data on the predictive importance of molecular and genetic characteristics in HGPUC suggest a strong similarity between high-grade and invasively growing tumours. PUNLMP and LGPUC are genetically stable in contrast to the high grade neoplasias, which show numerous chromosomal aberrations, a high frequency of p53, Her2, EGFR or Ras overexpression and loss of p21 or p27 comparable to that seen in invasive cancers [4]. All in all, a thoroughly evaluated molecular marker with sufficient predective power to be used in clinical routine for HGPUC has not as yet been established Clinical implications Although the frequency of tumour recurrence and progression for cohorts with HGPUC is slightly lower than corresponding rates for TaG3-tumours as graded according to the 1973 WHO classification, this difference does not justify a change in the Table 7 Recurrence, progression and mortality in HGPUC Study No. of cases % Tumour recurrence % Stage progression % Tumour related mortality Mean follow-up Holmäng et al. [39] n.a. >5 yr a Oosterhuis et al. [28] mo Samaratunga et al. [31] 29 n.a. (0.047 rec./yr) 51 b n.a mo Campbell et al. [40] n.a. 10 yr a Mean percentage n.a.: not available. a No mean follow-up period available. b 90 months actuarial risk of progression.

10 92 eau-ebu update series 4 (2006) follow-up regimen for these high-risk lesions. According to the recent EAU guidelines on bladder cancer [46] we recommend immediate bladder instillation followed by a 4 8-week course of topical therapy. Life-long follow-up including cystoscopy and cytology for patients with HGPUC is advisable. 4. Conclusions The main advantage of the 1998 WHO/ISUP and the 2004 WHO classification of non-invasive urothelial tumours over the 1973 WHO typing system is, that in the recent classifications detailed histological criteria have been delineated for each entity (Tables 1 and 3). The use of standardized definition and nomenclature will allow valid comparison of treatment results and should favourably affect patient management. However, the intra- and inter-observer reproducibility of the recent WHO and WHO/ISUP classification of noninvasive urothelial tumours has not been sufficiently evaluated by clinical studies so far. As to whether the subgrouping of low-grade urothelial tumours as PUNLMP and LGPUC in the recent WHO classifications adds prognostic value as compared with the 1973 typing system: this is, as yet, inconclusive and has to be elucidated by further studies. The detailed histopathological definition of flat urothelial lesions with reactive changes, UD and CIS in the 2004 WHO classification should improve diagnostic reproducibility and should therefore support further molecular and clinical characterization, particularly in UD. Immunohistochemical and molecular markers do hold great promise for the future in the classification of bladder neoplasms. However, biomarkers for enhancing the prognostication of non-invasive bladder tumours, are not yet adequately established. Until the prognostic significance of the 2004 WHO classification is further tested and proved valid by future studies, it is recommended that tumours should be graded according to both the 1973 and 2004 WHO classification. 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12 94 eau-ebu update series 4 (2006) cancer: a meta-analysis of the publshed results of randomized clinical trials. J Urol 2004;171: [48] Holmäng S, Hedelin H, Anderström C, Holmberg E, Busch C, Johannson SL. Recurrence and progression in low grade papillary urothelial tumors. J Urol 1999;162: [49] Ramos D, Navarro S, Villamon R, Gil-Salmon M, Llombart- Bosch A. Cytokeratin expression patterns in low-grade papillary urothelial neoplasms of the urinary bladder. Cancer 2003;97: [50] Wild PJ, Herr A, Wissmann C, Stoehr R, Rosenthal A, Zaak D, et al. Gene expression profiling of progressive papillary noninvasive carcinomas of the urinary bladder. Clin Cancer Res 2005;11: [51] Cordon-Cardo C, Cote RJ, Sauter G. Genetic and molecular markers of urothelial premalignancy and malignancy. Scand J Urol Nephrol Suppl 2000;205: [52] Haukaas S, Daehlin L, Maartmann-Moe H, Ulvik NM. The long-term outcome in patients with superficial transitional cell carcinoma of the bladder: a single-institutional experience. BJU Int 1999;83: [53] Herr HW. Tumor progression and survival of patients with high grade, noninvasive papillary (TaG3) bladder tumors: 15 year outcome. J Urol 2000;163:60 2. [54] Mostofi FJ, Davis CJ, Sesterhenn IA, editors. Histological Typing of urinary bladder tumours. In: World Health Organisation international histological classification of tumours. Berlin, Heidelberg, New York, Tokio: Springer Verlag; p [55] Cheng L, Neumann RM, Bostwick DG. Papillary urothelial neoplasms of low malignant potential. Clinical and biological implications. Cancer 1999;86: [56] Alvarez Kindelan J, Lopez Beltran A, Requena Tapia MJ. Urothelial papillary neoplasms of low malignant potential. Retrospective studies. Actas Urol Esp 2000;24: [57] Fujii Y, Kawakami S, Koga F, Nemoto T, Kihara K. Long-term outcome of bladder papillary urothelial neoplasms of low malignant potential. BJU International 2003;92: CME questions Please visit to answer these CME questions on-line. The CME credits will then be attributed automatically. 1. The 2004 World Health Organization (WHO) classification for non-invasive urothelial tumours A. is concurrent with the 1998 WHO/International Society of Urologic Pathologists (ISUP) classification for urothelial tumours. B. subdivides urothelial carcinoma in situ (CIS) into a low- and high-grade group. C. provides detailed guidelines for clinical follow-up for each lesion. D. is identical to the 1973 WHO typing system for bladder tumours with regard to flat urothelial lesions. 2. Regarding papillary urothelial neoplasms of low malignant potential (PUNLMP) according to the 2004 WHO classification for bladder tumours, which of the following statements is correct: A. The term PUNLMP according to the 2004 WHO classification and superficial low-grade transitional cell carcinoma can be used synonymously. B. PUNLMP lesions rarely progress (<5% stage progression rate) to invasive urothelial tumours. C. PUNLMP lesions rarely recurr (<10% recurrence rate). D. PUNLMP lesions show molecular and genetic characteristics similar to high grade urothelial cancer or carcinoma in situ (CIS). 3. Regarding PUNLMP lesions and papillary urothelial carcinoma, low-grade (LGPUC) according to the 2004 WHO classification, which of the following statements is correct: A. PUNLMP and LGPUC demonstrated no difference regarding recurrence rates in recent studies. B. In recent studies LGPUC showed stage progression rates in 40 50% of cases within a 5- year follow-up. C. The clinical and prognostic relevance of the subgrouping of low-grade urothelial tumours as PUNLMP and LGPUC in the 2004 WHO classification needs further validation by clinical studies. D. The majority of LGPUCs were originally considered grade1 transitional cell carcinomas according to the 1973 WHO typing system for bladder tumours. 4. Urothelial atypia A. is a well defined entity according to the 1973 WHO typing system for bladder tumours. B. as defined by the 2004 WHO classification for bladder tumours is an obligatory premalignant lesion. C. of unknown significance (AUS) according to the 2004 WHO classificaton is a descriptive term used in diagnostically difficult cases and patients diagnosed with this lesion need further follow-up. D. is subdivided into reactive atypia and premalignant atypia according to the recent WHO classification. 5. Urothelial papilloma according to the 2004 WHO classification for bladder tumours A. is composed of a delicate fibrovascular core covered by urothelium indistinguishable from that of normal urothelium. B. is histopathologically characterized by a maximum of 6 cell layers.