Comparison of urine cytology diagnostic reports before and after the implementation of the Paris System classification system in China.

OBJECTIVE: In 2013, The Paris System for Reporting Urinary Cytology (TPS) was developed as a uniform practical urine cytology system that could be applied worldwide. Here, we investigated the effectiveness of TPS diagnostic approach compared with that of the traditional urine cytological diagnosis method used in China. METHODS: Based on the diagnostic criteria of TPS, 412 urine samples from 143 patients with histological follow-up data were retrospectively analysed, and the diagnoses were compared with the original cytological diagnoses. RESULTS: In total, 110 patients were histologically diagnosed with high-grade urothelial carcinoma (HGUC), and 33 patients were diagnosed with low-grade urothelial neoplasia. Based on the traditional urine cytological analysis method, 50 patients (34.9%) were diagnosed as negative, 48 patients (33.6%) were diagnosed as having atypical urothelial cells, and 45 patients (31.5%) were diagnosed as positive. After reclassification using TPS, urine samples from 11 cases (7.7%) were categorised as unsatisfactory, 34 cases (23.8%) were negative, 21 cases (14.7%) were categorised as having atypical urothelial cells, 12 cases (8.4%) were diagnosed as suspicious for HGUC, 59 cases (41.2%) were diagnosed with HGUC, and six cases (4.2%) were reclassified as having low-grade urothelial neoplasia. Thus, after implementing TPS criteria, the sensitivity for positive malignancy diagnoses (HGUC alone) increased from 38.2% to 50.9%, while the specificity of the diagnosis was barely changed. CONCLUSIONS: The Paris System for Reporting Urinary Cytology greatly contributes to the standardisation of urine cytology reports and significantly improves the diagnostic sensitivity for HGUC.

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.

The updated points of TNM classification of urological cancers in the 8th edition of AJCC and UICC.

The Tumor-Node-Metastasis (TNM) staging system, jointly developed by the American Joint Commission on Cancer (AJCC) and the Union for International Cancer Control (UICC), is widely employed in clinical practice and research on patients with cancer. The definitions of TNM classification have recently been changed, improving patient stratification for management and prognosis. As the feature of new editions, biomarkers which are necessary for the stratification of patients are included to adapt for personalized medicine. Although it would be ideal for the AJCC and UICC have identical TNM staging systems, there are some differences between these two publications. In this review, we introduce the significant changes and differences in the eighth edition of the AJCC and UICC TNM staging systems for urologic cancers and summarize the evidence supporting these changes.

[Comparison of UICC and AJCC 8th edition TNM classifications in uropathology]. / Comparaison des classifications TNM des 8es éditions de l'UICC et de l'AJCC en uropathologie.

The pTNM stage is one of the most important parameters in the handling of tumor patients. The pathologist plays a major role in the determination of the stage. The classifications undergo an evolution according to the state of art. The TNM system is used worldwide and allows to precise the tumor (T) and lymph node stage and the presence of distant metastasis. This system helps to stratify patient groups and determine their prognosis. In 2017, the Union for International Cancer Control (UICC) and the American Joint Committee on Cancer (AJCC) published their 8th edition. Unluckily several differences exist between both classifications. The UICC neglected to make several recommendations according to the International Society of Urological Pathology (ISUP) decisions, which organises the consensus in uropathology.

[Morphological and immunohistochemical characteristics of the molecular subtypes of urothelial carcinomas]. / Morfologicheskaia i immunogistokhimicheskaia kharakteristika molekuliarnykh podtipov urotelial'nykh kartsinom.

The molecular subtypes of urothelial carcinoma in each classification scheme have characteristic immunohistochemical features. At the same time, the results of conducted studies often demonstrate a discrepancy between the genomic profile of urothelial carcinoma and its immunophenotype, which complicates the immunohistochemical verification of the molecular subtypes of these tumors. OBJECTIVE: To compare the morphological and immunophenotypic characteristics of the molecular subtypes of urothelial carcinoma. MATERIAL AND METHODS: Surgical specimens from 196 patients diagnosed with urothelial carcinoma of the renal pelvis and bladder were investigated. Paraffin-embedded sections were immunohistochemically examined using the standard protocol. Antibodies against CK5/6, CK17, Rb1 (Dako), CK14, CK18, CK20, Cyclin D1, Cyclin E1, Cyclin A, Cyclin B, Chromogranin, E-Cadherin, P-Cadherin, p16, Uroplakin II, TUBB2B, Vimentin, ZEB-2 ('Novocastra'), CD44, GATA-3, and Uroplakin III ('Cell Marque') were used. RESULTS: Out of 68 (35%) superficial papillary urothelial carcinomas, 24 (12%) tumors constituted Molecular Class I and 12 (6%) and 32 (16%) ones did Molecular Classes II and III, respectively. Of the 128 (65%) muscle-invasive urothelial carcinomas, 57 (29%) tumors were referred to as the luminal-papillary molecular subtype, and 24 (12%) and 14 (7%) were as the luminal-infiltrated and luminal molecular subtypes, respectively. The basal squamous molecular subtype was verified in 31 (16%) neoplasms and the neuronal phenotype was detected in 2 (1%) cases. CONCLUSION: Most pT1 tissues correspond to Molecular Class II. In the muscle-invasive urothelial carcinoma group, the neoplasms with a luminal phenotype predominate over the tumors with basal and neuronal phenotypes.

Pathology Imagebase-a reference image database for standardization of pathology.

AIMS: Despite efforts to standardize histopathology practice through the development of guidelines, the interpretation of morphology is still hampered by subjectivity. We here describe Pathology Imagebase, a novel mechanism for establishing an international standard for the interpretation of pathology specimens. METHODS AND RESULTS: The International Society of Urological Pathology (ISUP) established a reference image database through the input of experts in the field. Three panels were formed, one each for prostate, urinary bladder and renal pathology, consisting of 24 international experts. Each of the panel members uploaded microphotographs of cases into a non-public database. The remaining 23 experts were asked to vote from a multiple-choice menu. Prior to and while voting, panel members were unable to access the results of voting by the other experts. When a consensus level of at least two-thirds or 16 votes was reached, cases were automatically transferred to the main database. Consensus was reached in a total of 287 cases across five projects on the grading of prostate, bladder and renal cancer and the classification of renal tumours and flat lesions of the bladder. The full database is available to all ISUP members at www.isupweb.org. Non-members may access a selected number of cases. CONCLUSIONS: It is anticipated that the database will assist pathologists in calibrating their grading, and will also promote consistency in the diagnosis of difficult cases.

[From new genetic and histological classifications to direct treatment]. / Carcinome urothélial : des classifications histologiques et moléculaires vers un traitement adéquat.

The most important criterion for optimal cancer treatment is a correct classification of the tumour. During the last three years, several very important progresses have been made with a better definition of urothelial carcinoma (UC), especially from a molecular point of view. We start having a global understanding of UC, although many details are still not completely understood.

Lithium and renal and upper urinary tract tumors - results from a nationwide population-based study.

OBJECTIVES: A recent alarming finding suggested an increased risk of renal tumors among long-term lithium users. The objectives of the present study were to estimate rates of renal and upper urinary tract tumors (RUT), malignant and benign, among individuals exposed to successive prescriptions for lithium, anticonvulsants, and other psychotropic agents used for bipolar disorder, and among unexposed individuals. METHODS: This was a nationwide, population-based longitudinal study including time-specific data from all individuals exposed to lithium (n = 24,272) or anticonvulsants (n = 386,255), all individuals with a diagnosis of bipolar disorder (n = 9,651), and a randomly selected sample of 1,500,000 from the Danish population. The study period was from 1995 to 2012, inclusive. Outcomes were hazard rate ratios (HR) for RUT in three groups: (i) combined malignant and benign, (ii) malignant, and (iii) benign. Analyses were adjusted for the number of prescriptions for lithium/anticonvulsants, antipsychotic agents, antidepressants, and use of all other types of medication; age; gender; employment status; calendar year; and a diagnosis of bipolar disorder. RESULTS: Continued treatment with lithium was not associated with increased rates of RUT [adjusted HR malignant or benign: 0.67-1.18, p (trend) = 0.70; adjusted HR malignant: 0.61-1.34, p (trend) = 0.90; adjusted HR benign: 0.74-1.18, p (trend) = 0.70]. Similarly, continued treatment with anticonvulsants was not associated with increased rates of RUT [adjusted HR malignant or benign: 0.97-1.18, p (trend) = 0.10; adjusted HR malignant: 0.82-1.15, p (trend) = 0.80; adjusted HR benign: 0.94-1.36, p (trend) = 0.20]. The associations were confirmed among the 9,651 patients with a diagnosis of bipolar disorder. CONCLUSIONS: Treatment with lithium is not associated with increased rates of RUT.

[Cytology in uropathological diagnostics]. / Zytologie in der uropathologischen Diagnostik.

Cytology in uropathological diagnostics is mainly performed for oncological purposes. The assessment of malignancy by urothelial cell morphology is therefore decisive; however, cytology is only sensitive enough to detect high-grade tumor cells and the different low-grade tumors cannot be reliably diagnosed. Thus, the four-tier classification system of cytological findings (i.e. negative, atypical cells but significance uncertain, suspicious and positive) refers to high-grade tumor cells only. Furthermore, for valid cytological diagnostics not only the cytological specimen but also clinical information on cystoscopy findings and, if applicable, a biopsy should be evaluated together. In difficult differential diagnostic settings, e.g. differentiation between reactive versus neoplastic atypia or difficult to access lesions in the upper urinary tract, additional fluorescence in situ hybridization of cytological preparations might be helpful. At the moment there are no indications for further immunocytology or additional biomarker tests.

Pathology focused review of morphologic subtypes and molecular variants of urothelial carcinoma with an emphasis on clinical/treatment relevance.

Urothelial carcinoma (UC) has significant morbidity, mortality, and remains the most financially costly carcinoma to manage and treat. This review will cover special morphologic features of UC that may be noted by the pathologist and any subsequent significance in terms of clinical management or treatment considerations as mentioned or recommended in the latest WHO 2022 classification of GU tumors. Many important potentially therapy altering morphologic findings can be consistently identified and reported on routine microscopic examination of hematoxylin and eosin (H&E) stained slides. Furthermore, there has been a rapid advancement of molecular diagnostics and tailored therapies throughout oncology, and we will briefly highlight some of these as they relate to the management of UC. We will actively attempt to limit the discussion of histologic descriptions or pathologic diagnostic criteria of these entities and focus rather on the recognition of their importance/implication for clinicians who must make clinical management decisions based upon these findings. Finally, the importance of open lines of communication with the pathologists who review clinical specimens as well as their practice and reporting methods cannot be overstated.

Proliferative and nonproliferative lesions of the rat and mouse urinary system.

The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP), and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature for classifying lesions observed in the urinary tract of rats and mice. The standardized nomenclature of urinary tract lesions presented in this document is also available electronically on the Internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous developmental and aging lesions as well as those induced by exposure to test materials. A widely accepted and utilized international harmonization of nomenclature for urinary tract lesions in laboratory animals will decrease confusion among regulatory and scientific research organizations in different countries and provide a common language to increase and enrich international exchanges of information among toxicologists and pathologists.

Updates in Histologic Grading of Urologic Neoplasms.

CONTEXT.­: Tumor histology offers a composite view of the genetic, epigenetic, proteomic, and microenvironmental determinants of tumor biology. As a marker of tumor histology, histologic grading has persisted as a highly relevant factor in risk stratification and management of urologic neoplasms (ie, renal cell carcinoma, prostatic adenocarcinoma, and urothelial carcinoma). Ongoing research and consensus meetings have attempted to improve the accuracy, consistency, and biologic relevance of histologic grading, as well as provide guidance for many challenging scenarios. OBJECTIVE.­: To review the most recent updates to the grading system of urologic neoplasms, including those in the 2016 4th edition of the World Health Organization (WHO) Bluebook, with emphasis on issues encountered in routine practice. DATA SOURCES.­: Peer-reviewed publications and the 4th edition of the WHO Bluebook on the pathology and genetics of the urinary system and male genital organs. CONCLUSIONS.­: This article summarizes the recently updated grading schemes for renal cell carcinoma, prostate adenocarcinomas, and bladder neoplasms of the genitourinary tract.

What Is the Significance of Variant Histology in Urothelial Carcinoma?

CONTEXT: Urothelial carcinoma can exhibit a wide range of variant morphologies. Many variants present diagnostic challenges and carry clinical implications that inform prognosis and treatment decisions. OBJECTIVE: To provide an overview of the diagnostic, therapeutic, and prognostic significance of histological variants of urothelial carcinoma. EVIDENCE ACQUISITION: A PubMed/MEDLINE-based literature search was conducted using the key terms "urothelial carcinoma", "variant histology", "nested", "micropapillary", "microcystic", "sarcomatoid", "squamous differentiation", "glandular differentiation", "clear cell", "plasmacytoid", "lymphoepithelioma-like carcinoma", "squamous cell carcinoma", "small cell carcinoma", "adenocarcinoma", "radiotherapy", "neoadjuvant chemotherapy", and "adjuvant chemotherapy". EVIDENCE SYNTHESIS: The incidence of variant histology is increasing due to improved recognition. Nonetheless, diagnosis can pose challenges due to sampling limitations and interobserver variability. Although associated with advanced disease at presentation, survival outcomes for most variants do not differ significantly compared with pure urothelial carcinoma of the same stage. Controversy exists regarding optimal management due to the low quality of available evidence. For most cases, radical cystectomy with pelvic lymph node dissection (with neoadjuvant chemotherapy when appropriate) represents the standard of care. Small cell carcinoma and lymphoepithelioma-like carcinoma appear to be particularly chemosensitive. CONCLUSIONS: Accurate identification of variant histological subtypes is an important part of risk stratification, as these variants exhibit aggressive biological behaviour. Variant histology tumours are associated with advanced disease at presentation, which must be considered when counselling patients regarding survival outcomes. Optimal management remains to be defined but in most cases; neoadjuvant chemotherapy and radical cystectomy with pelvic lymph node dissection remains the mainstay of treatment. PATIENT SUMMARY: It is important to recognise histological variants of urothelial carcinoma as they indicate aggressive disease. When compared with patients with pure urothelial carcinoma of the same disease stage, survival does not appear to be significantly worse. In most cases, patients with invasive variant histology should be treated with neoadjuvant chemotherapy and radical cystectomy. Take Home Messages Accurate identification of variant histology is important as it exhibits aggressive biological behaviour and affects treatment. Although associated with advanced disease at presentation, with appropriate treatment, survival outcomes are not significantly different compared with pure urothelial carcinoma of the same stage.

Single-Port Robotic Urological Surgery Using Purpose-Built Single-Port Surgical System: Single-Institutional Experience With the First 100 Cases.

OBJECTIVES: To present a comprehensive report regarding our experience with single-port robotic surgery in our first 100 consecutive patients. We describe the diversity of procedures that can be performed with this platform as well as the challenges and complications we had with the application of this novel technology. METHODS: Between September 2018 and August 2019, data on 100 patients who underwent single-port robotic surgery were consecutively collected. Preoperative, intraoperative and early postoperative outcomes after various urologic procedures were recorded and analyzed. RESULTS: During the study period, 100 patients (age [range] 35-84 years; 88 [88%] Male) underwent various single-port robotic surgeries for different indications (Retroperitoneal [n = 14], Pelvic surgeries [n = 86]). Transperitoneal (n = 37), extraperitoneal (n = 53) and transvesical (n = 10) approaches have been used to access the target organs. Of these procedures, 73 (73%) were for different oncological indications: Radical prostatectomy (n = 60), Partial nephrectomy (n = 6), Retroperitoneal lymph node dissection (n = 1) and Radical cystectomy with intracorporeal diversion (n = 6). Surgery was successfully completed in all but 1 patient, in whom the surgery was converted to open surgery due to dense adhesions and failure to progress. Grades II-III postoperative complications were detected in (n = 9) patients. CONCLUSION: The purpose-built single-port robotic platform can be safely incorporated into the minimally invasive armamentarium. A wide range of pelvic and retroperitoneal urological procedures can be done with different approaches using this platform. Randomized trials with adequate sample size and postoperative follow up period is advisable for further evaluation of the outcomes and to determine the added value of this emerging technology.

HER2 Status in Molecular Subtypes of Urothelial Carcinoma of the Renal Pelvis and Ureter.

INTRODUCTION: Erb-b2 receptor tyrosine kinase 2 (ERBB2, also known as HER2) gene amplification or protein overexpression occurs in certain types of urothelial carcinomas. Molecular pathologic classification of urinary bladder cancer using immunohistochemistry has identified basal and luminal subtypes with differing prognoses, but the HER2 status of these subtypes has not been investigated. In addition, research on urothelial carcinoma of the renal pelvis and ureter (UCRPU) has not progressed because of its rarity, though its prognosis is worse than that of bladder cancer. In this study, we evaluated the clinical significance of HER2 status in molecular subtypes of UCRPU. MATERIALS AND METHODS: HER2 status (protein overexpression and/or gene amplification) and molecular subtyping were determined for 148 cases of UCRPU (83 and 65 cases in the renal pelvis and ureter, respectively), using immunohistochemistry and fluorescent in situ hybridization, and compared with clinicopathologic factors. RESULTS: Subtype analysis revealed that the cases were 46% basal and 54% luminal. HER2 protein overexpression and/or gene amplification was observed in 14% of UCRPU cases and was significantly more frequent in the luminal subtype than in the basal (22% vs. 4%; P = .0030). Univariate analysis showed that the overall survival of patients with HER2-positive UCRPU was significantly shorter than those with HER2-negative tumors. CONCLUSIONS: HER2 protein overexpression and gene amplification were specifically observed in the luminal subtype of UCRPU, suggesting that these cases may respond to HER2-targeted therapies like trastuzumab.

Histological variants of urothelial carcinoma: diagnostic, therapeutic and prognostic implications.

It is well established that invasive urothelial carcinoma, involving the urinary bladder and renal pelvis, has marked propensity for divergent differentiation. In recent years, several 'variant' morphologies have been described and most have been recognized in the 2004 World Health Organization Classification. These histological variants of urothelial carcinoma have clinical significance at various levels, including diagnostic, that is, awareness of the morphological variant is essential in order to avoid diagnostic misinterpretations; prognostic for patient risk stratification; and therapeutic, where a diagnostic assignment of a particular variant may be associated with the administration of a therapy distinctive from that used in conventional invasive urothelial carcinoma. The diagnoses of micropapillary urothelial carcinoma, small-cell carcinoma, lymphoepithelioma-like carcinoma and sarcomatoid carcinoma are prime examples where treatment protocols may be different than the usual muscle-invasive bladder cancer. This review discusses the variants of urothelial carcinoma, outlining for each the diagnostic features, differential diagnostic considerations and the clinical significance.

[Urological cancer].

Chemotherapy has a major role in the multidisciplinary treatment of urological cancer. Especially cisplatin-based combination chemotherapy plays a central role in the treatment of bladder cancer and testicular cancer. Intravesical chemotherapy for non-muscle-invasive bladder cancer has a clear impact on tumor recurrence when immediately instilled after TURBT and when used in an adjuvant setting. However, there is no clear evidence of an impact on progression. The consensus is that anticancer drugs should be used preferentially over BCG for low-risk disease. Systemic combination chemotherapy for muscle-invasive bladder cancer yields high response rates but suboptimal longterm outcomes for advanced bladder cancer. GC therapy provides similar efficacy in terms of overall survival and progression-free survival compared with M-VAC but with a superior safety profile. In the treatment of prostate cancer, docetaxel has become the treatment of choice for patients with hormone refractory cancer. A treatment strategy for testicular cancer has been established, and a high response rate is obtained even in advanced cancer. However, further innovations in treatment for patients with poor prognosis are required. Thus, new anticancer drugs such as taxanes and gemcitabine were added to cisplatin-based chemotherapy, and a treatment of urological cancer is progressing.

Grading of Urothelial Carcinoma and The New "World Health Organisation Classification of Tumours of the Urinary System and Male Genital Organs 2016".

CONTEXT: In the management of urothelial carcinoma, determination of the pathological grade aims at stratifying tumours into different prognostic groups to allow evaluation of treatment results, and optimise patient management. This article reviews the principles behind different grading systems for urothelial bladder carcinoma discussing their reproducibility and prognostic value. OBJECTIVE: This paper aims to show the evolution of the World Health Organisation (WHO) grading system, discussing their reproducibility and prognostic value, and evaluating which classification system best predicts disease recurrence and progression. The most optimal classification system is robust, reproducible, and transparent with comprehensive data on interobserver and intraobserver variability. The WHO published an updated tumour classification in 2016, which presents a step forward, but its performance will need validation in clinical studies. EVIDENCE ACQUISITION: Medline and EMBASE were searched using the key terms WHO 1973, WHO/International Society of Urological Pathology 1998, WHO 2004, WHO 2016, histology, reproducibility, and prognostic value, in the time frame 1973 to May 2016. The references list of relevant papers was also consulted, resulting in the selection of 48 papers. EVIDENCE SYNTHESIS: There are still inherent limitations in all available tumour classification systems. The WHO 1973 presents considerable ambiguity for classification of the G2 tumour group and grading of the G1/2 and G2/3 groups. The 2004 WHO classification introduced the concept of low-grade and high-grade tumours, as well as the papillary urothelial neoplasm of low malignant potential category which is retained in the 2016 classification. Furthermore, while molecular markers are available that have been shown to contribute to a more accurate histological grading of urothelial carcinomas, thereby improving selection of treatment for a given patient, these are not (yet) part of standard clinical practice. CONCLUSIONS: The prognosis of patients diagnosed with urothelial carcinoma greatly depends on correct histological grading of the tumour. There is still limited data regarding intraobserver and interobserver variability differences between the WHO 1973 and 2004 classification systems. Additionally, reproducibility remains a concern: histological differences between the various types of tumour may be subtle and there is still no consensus amongst pathologists. The recent WHO 2016 classification presents a further improvement on the 2004 classification, but until further data becomes available, the European Association of Urology currently recommends the use of both WHO 1973 and WHO 2004/2016 classifications. PATIENT SUMMARY: Bladder cancer, when treated in time, has a good prognosis. However, selection of the most optimal treatment is largely dependent on the information your doctor will receive from the pathologist following evaluation of the tissue resected from the bladder. It is therefore important that the classification system that the pathologist uses to grade the tissue is transparent and clear for both urologists and pathologists. A reliable classification system will ensure that aggressive tumours are not misinterpreted, and less aggressive cancer is not overtreated.