The Genitourinary Pathology Society Update on Classification of Variant Histologies, T1 Substaging, Molecular Taxonomy, and Immunotherapy and PD-L1 Testing Implications of Urothelial Cancers

A Systematic Review on the Current Landscape of T1 Bladder Cancer Substaging

OBJECTIVE

To conduct a systematic review on the current state of T1 bladder tumor substaging. These neoplasms display significant heterogeneity in oncological behavior and prognosis, leading to the proposal of various substaging methods. Our aim was to investigate the potential diagnostic and prognostic value of substaging in stage T1 bladder cancer for better oncologic outcomes.

METHODS

A literature search using MEDLINE, EMBASE and Cochrane Library databases was conducted in March 2024 to identify relevant studies on T1 urothelial bladder cancer staging. A systematic review of included articles was performed following the PRISMA guideline statement. Literature search was conducted in English.

RESULTS

Overall, 63 studies published between 1990 and 2024 were included for final review including a total number of 8207 bladder tumor patients subject to T1 substaging. Various substaging methods have been developed, broadly classified into histometric (anatomy-based) and micrometric (semiquantitative) techniques. Advanced stages have been consistently associated with worse prognosis and need for a more radical therapeutic approach. A standardized, validated, unified substaging report system is lacking.

CONCLUSIONS

T1 substaging is a strong predictor of oncologic outcomes. Micrometric methods seem to be more reproducible and precise than histometric techniques in terms of feasibility and prognostic value. Standardization and validation of the technique could potentially enhance the bladder cancer treatment algorithm. We would like to provide an explanation regarding why our systematic review was not prospectively registered in the PROSPERO database. Initially, this review was conceived as part of a doctoral thesis (PhD) project, and there was no intention to publish it. Although we strictly adhered to the PRISMA guidelines from the beginning, the decision to publish the review was made only after most of the data had been extracted. At that point, retrospectively registering it in PROSPERO would have been somewhat unethical, which is why we chose not to register it. We fully recognize the importance of actively registering systematic reviews, as it is the proper and ethical way to proceed in these cases. We remain committed to transparency and best practices in research and believe that prospective registration is crucial for ensuring the integrity and credibility of systematic reviews.

[German expert consensus on programmed cell death ligand 1 (PD-L1) testing in perioperative systemic therapy of muscle invasive bladder cancer]

The risk of recurrence in patients with muscle invasive bladder cancer (MIBC) after radical cystectomy depends on the pathological tumor stage. In particular, patients with lymph node metastasis (pN+), locally advanced (≥pT3), or residual muscle invasive tumor despite neoadjuvant chemotherapy are at high risk. Currently, the importance of adjuvant therapy with immune checkpoint inhibitors is increasing in the context of perioperative systemic therapeutic concepts. The indication for the PD‑1 inhibitor nivolumab currently approved in the European Union requires testing of PD-L1 (programmed cell death ligand 1) protein expression by immunochemistry in tumor tissue. Focusing on MIBC patients at high risk of recurrence, new questions arise regarding the implementation and interpretation of PD-L1 testing. An interdisciplinary group of experts from Germany has discussed relevant issues from a clinicopathological point of view and developed practical recommendations to facilitate the implementation of validated and quality-assured PD-L1 testing for the approved indications in daily clinical practice.

A single-center retrospective comparison of pT1 substaging methods in bladder cancer

Substaging of T1 urothelial cancer is associated with tumor progression and its reporting is recommended by international guidelines. However, it has not been integrated in risk stratification tools and there is no agreement on the best method to use for its reporting. We aimed to investigate the applicability, interobserver variability, and prognostic value of histological landmark based and micrometric (aggregate linear length of invasive carcinoma (ALLICA), microscopic vs. extensive system, Rete Oncologica Lombarda (ROL) system) substaging methods. A total of 79 patients with the primary diagnosis of T1 urothelial cancer treated with conventional transurethral resection and adjuvant BCG therapy between 2000 and 2020 at the Medical University of Vienna were included. The anatomical and metrical substaging systems were evaluated using agreement rate, Cohen's kappa, Kendall's tau, and Spearman rank correlation. Prognostic value for high-grade recurrence or T2 progression was evaluated in uni- and multivariable analysis. Applicability and reproducibility were good to moderate and varied between substaging methods. Obstacles are mainly due to fragmentation of samples. Anatomical substaging was associated with progression in univariable and multivariable analysis. In our cohort, we could only identify anatomical landmark-based substaging to be prognostic for T2 progression. A major obstacle for proper pathological assessment is fragmentation of samples due to operational procedure. Avoiding such fragmentation might improve reproducibility and significance of pathological T1 substaging of urothelial cancer.

The Prognostic Significance of Histological Subtypes in Patients with Muscle-Invasive Bladder Cancer: An Overview of the Current Literature

Bladder cancer (BC) is the tenth most commonly diagnosed malignancy worldwide. In approximately 25% of cases, it presents as a muscle-invasive disease, requiring a radical treatment. Traditionally, the mainstay of treatment has been radical cystectomy (RC), but in the last decade, bladder-sparing treatments have been gaining growing interest. In particular, trimodal therapy (TMT) seems to yield survival results comparable to RC with less morbidity and better quality of life (QoL) outcomes. In this scenario, we aimed at shedding light on the role of the histological subtypes (HS) of BC and their prognostic significance in muscle-invasive BC (MIBC), treated either surgically or with TMT. We performed a narrative review to provide an overview of the current literature on this topic. When compared with patients diagnosed with conventional urothelial carcinoma (UC) of the same disease stage, survival did not appear to be significantly worse across the reports. But when sub-analyzed for separate subtype, some appeared to be independently associated with adverse survival outcomes such as the micropapillary, plasmacytoid, small-cell, and sarcomatoid subtypes, whereas others did not. Moreover, the optimal management remains to be defined, also depending on the therapeutic susceptibility of each histology. From this perspective, multi-disciplinary assessment alongside the routine inclusion of such entities in randomized clinical trials appears to be essential.

Prognostic value of micrometric substaging in pT1 bladder cancer patients treated with en-bloc transurethral resection

AIMS

We aimed to assess the oncological impact of micrometric extent of invasion in patients with pT1 bladder cancer (BCa) who underwent en-bloc resection for bladder tumour (ERBT).

METHODS AND RESULTS

We retrospectively analysed the records and specimens of 106 pT1 high-grade BCa patients who underwent ERBT. The extent of invasion, such as depth from basal membrane, number of invasive foci, maximum width of invasive focus, muscularis mucosae invasion and infiltration pattern (pattern A: solid sheet-like, nodular or nested growth, pattern B: trabecular, small cluster or single-cell pattern) were evaluated by a single genitourinary pathologist. The end-points were recurrence-free (RFS) and progression-free survival (PFS). Within a median follow-up of 23 months, overall, 36 patients experienced recurrence and 13 patients experienced disease progression. The 2-year PFS differed significantly depending on depth from basal membrane (< 1.3 mm: 94.8% versus ≧ 1.3 mm: 65.2%, P = 0.005), maximum width of invasive focus (< 4 mm: 91.7% versus ≧ 4 mm: 62.3%, P < 0.001), muscularis mucosae (MM) invasion (above MM = 96.1% versus into or beyond MM = 64.8%, P = 0.002) and infiltration pattern (pattern A: 100% versus pattern B: 83.3%, P = 0.037). In a multivariable analysis, MM invasion [hazard ratio (HR) = 4.54, 95% confidence interval (CI) = 1.25-16.5] and maximum width of invasive focus ≧ 4 mm (HR = 4.79, 95% CI = 1.25-16.5) were independent prognostic factors of progression.

CONCLUSIONS

En-bloc resection facilitates the evaluation of pathologic variables that might be useful in predicting disease recurrence and progression. In particular, not only the MM invasion but also the maximum width of invasion focus, reflecting the invasive volume, appear to be reliable prognosticators for disease progression.

Using machine learning to develop preoperative model for lymph node metastasis in patients with bladder urothelial carcinoma

BACKGROUND

Lymph node metastasis (LNM) is associated with worse prognosis in bladder urothelial carcinoma (BUC) patients. This study aimed to develop and validate machine learning (ML) models to preoperatively predict LNM in BUC patients treated with radical cystectomy (RC).

METHODS

We retrospectively collected demographic, pathological, imaging, and laboratory information of BUC patients who underwent RC and bilateral lymphadenectomy in our institution. Patients were randomly categorized into training set and testing set. Five ML algorithms were utilized to establish prediction models. The performance of each model was assessed by the area under the receiver operating characteristic curve (AUC) and accuracy. Finally, we calculated the corresponding variable coefficients based on the optimal model to reveal the contribution of each variable to LNM.

RESULTS

A total of 524 and 131 BUC patients were finally enrolled into training set and testing set, respectively. We identified that the support vector machine (SVM) model had the best prediction ability with an AUC of 0.934 (95% confidence interval [CI]: 0.903-0.964) and accuracy of 0.916 in the training set, and an AUC of 0.855 (95%CI: 0.777-0.933) and accuracy of 0.809 in the testing set. The SVM model contained 14 predictors, and positive lymph node in imaging contributed the most to the prediction of LNM in BUC patients.

CONCLUSIONS

We developed and validated the ML models to preoperatively predict LNM in BUC patients treated with RC, and identified that the SVM model with 14 variables had the best performance and high levels of clinical applicability.

Influence of lamina propria invasion extension on T1 high-grade non-muscle-invasive bladder cancer in patients undergoing BCG or radical cystectomy

OBJECTIVE

To evaluate the prognostic value of T1 substaging in patients treated with bacillus Calmette-Guérin (BCG) or immediate radical cystectomy (iRC).

MATERIALS AND METHODS

We performed an institutional review board-approved retrospective study analysing non-muscle-invasive bladder cancer (NMIBC) patients with pT1 disease treated with either BCG or iRC between 2000 and 2020. Lamina propria (LP) invasion characteristics were extracted from the pathology report. The Kaplan-Meier method was used to calculate overall survival (OS), cancer-specific survival (CSS) and metastasis-free survival (MFS). Multivariable Cox models were used to determine the association between progression-free survival (PFS) and characteristics in the BCG cohort. A logistic regression model explored the relationship between T1 substaging and upstaging to >pT2 at iRC.

RESULTS

A total of 411 T1 high-grade patients were identified. LP invasion characteristics were as follows: not specified: 115 (28%); focal/superficial (F/S): 147 (35.8%); and extensive/multifocal (E/M): 149 (36.2%). Overall, 303 patients (73.7%) received BCG, and 108 patients (26.3%) underwent iRC. The median (interquartile range) follow-up was 53 (32-96) months. Patients with E/M LP invasion were significantly more likely to undergo iRC (34% vs. 19%; P = 0.003). Patients with E/M LP invasion showed poorer MFS and CSS compared to those with F/S LP invasion when treated with BCG but not when treated with iRC. Among BCG-treated patients, progression occurred in 41 patients and E/M LP invasion was independently associated with progression after BCG (hazard ratio 5.3, 95% confidence interval [CI] 2.2-13.1; P < 0.001). T1 substaging was not associated with upstaging at RC (odds ratio 3.15, 95% CI 0.82-12.12; P = 0.095).

CONCLUSIONS

Extensive/multifocal LP invasion was associated with poor PFS, MFS and CSS in patients treated with BCG. T1 substaging provides valuable prognostic information and should be reported in pathology reports.

Current Advances in the Management of Nonurothelial Subtypes of Bladder Cancer

Urothelial cancer (UC) is the most common histology seen in bladder tumors. The 2022 WHO classification of urinary tract tumors includes a list of less common subtypes (formerly known as variants) for invasive UC which are considered high-grade tumors. This review summarizes the most recent advances in the management of selected nonurothelial subtypes of bladder cancer: squamous cell carcinoma, small cell carcinoma, sarcomatoid urothelial carcinoma, micropapillary carcinoma, plasmacytoid carcinoma, adenocarcinoma, and urachal carcinoma. The role of neoadjuvant and adjuvant chemotherapy has not been well characterized for most of these histologies, and prospective data are extremely limited. Participation in clinical trials is recommended in advanced disease.

Updates on Urinary Bladder Tumors With Neuroendocrine Features

The most common neuroendocrine tumor in the urinary bladder is small cell carcinoma, which can be pure or mixed with components of urothelial or other histologic subtypes. Large cell neuroendocrine carcinoma of the bladder is rare and remains ill-defined but is increasingly recognized. Well-differentiated neuroendocrine tumor and paraganglioma can arise in the bladder but are very rare in this location. Recent advances in molecular characterization allowed for better classification and may offer improved stratification of these tumors.

Aberrant expression of GATA3 in metastatic adenocarcinoma of the prostate: an important pitfall

AIMS

The distinction of high-grade prostate cancer (PCa) from poorly differentiated urothelial carcinoma (UC) can be somewhat challenging on clinical and morphological grounds alone, yet it is of great importance for prognostication and choice of treatment. GATA3 is a useful immunohistochemical marker to confirm urothelial origin. However, recent works report strong GATA3 immunoexpression in primary high-grade PCa. The aim of this study was to explore GATA3 expression specifically in metastatic PCa.

METHODS AND RESULTS

The pathology databases of four tertiary institutions were queried for cases of metastatic PCa. Available slides and clinical records were reviewed by experienced genitourinary pathologists. Prostatic markers (PSA, PSAP, NKX3.1) and GATA3 immunohistochemistry were performed. A total of 163 metastatic PCa cases were included. At least one prostate marker was positive in each case of non-regional distant metastasis, confirming prostatic origin. GATA3 strong staining was found in four (2.5%) cases: two liver, one bone and one non-regional lymph-node metastases. All four patients had Grade Group 5 PCa at the initial diagnosis. The metastatic prostatic adenocarcinomas were solid, either with no gland formation (n = 3) or with only focal cribriforming (n = 1).

CONCLUSIONS

To our knowledge, this is the first study exploring GATA3 expression specifically in metastatic PCa. Despite being infrequent, GATA3 positivity in high-grade PCa may lead to misdiagnosis, with clinical implications. We recommend a panel of immunohistochemical markers, both prostatic and urothelial, for ruling out UC, either in primary tumour samples or in the event of metastases of unknown primary, when a genitourinary origin is suspected.

Development and validation of a preoperative nomogram to predict lymph node metastasis in patients with bladder urothelial carcinoma

PURPOSE

Predicting lymph node metastasis (LNM) in patients with bladder urothelial carcinoma (BUC) before radical cystectomy aids clinical decision making. Here, we aimed to develop and validate a nomogram to preoperatively predict LNM in BUC patients.

METHODS

Patients with histologically confirmed BUC, who underwent radical cystectomy and bilateral lymphadenectomy, were retrospectively recruited from two institutions. Patients from one institution were enrolled in the primary cohort, while those from the other were enrolled in the external validation cohort. Patient demographic, pathological (using transurethral resection of the bladder tumor specimens), imaging, and laboratory data were recorded. Univariate and multivariate logistic regression analyses were performed to explore the independent preoperative risk factors and develop the nomogram. Internal and external validation was conducted to assess nomogram performance.

RESULTS

522 and 215 BUC patients were enrolled in the primary and external validation cohorts, respectively. We identified tumor grade, infiltration, extravesical invasion, LNM on imaging, tumor size, and serum creatinine levels as independent preoperative risk factors, which were subsequently used to develop the nomogram. The nomogram showed a good predictive accuracy, with area under the receiver operator characteristic curve values of 0.817 and 0.825 for the primary and external validation cohorts, respectively. The corrected C-indexes, calibration curves (after 1000 bootstrap resampling), decision curve analysis results, and clinical impact curves demonstrated that the nomogram performed well in both cohorts and was highly clinically applicable.

CONCLUSION

We developed a nomogram to preoperatively predict LNM in BUC, which was highly accurate, reliable, and clinically applicable.

En Bloc Resection Versus Conventional TURBT for T1HG Bladder Cancer: A Propensity Score-Matched Analysis

BACKGROUND

We aimed to assess the clinical, oncological, and pathological impact of en bloc resection of bladder tumors (ERBT) compared with conventional transurethral resection of bladder tumors (cTURBT) for pT1 high-grade (HG) bladder cancer.

PATIENTS AND METHODS

We retrospectively analyzed the record of 326 patients (cTURBT: n = 216, ERBT: n = 110) diagnosed with pT1 HG bladder cancer at multiple institutions. The cohorts were matched by one-to-one propensity scores based on patient and tumor demographics. Recurrence-free survival (RFS), progression-free survival (PFS), cancer-specific survival (CSS), and perioperative and pathologic outcomes were compared. The prognosticators of RFS and PFS were analyzed using the Cox proportional hazard model.

RESULTS

After matching, 202 patients (cTURBT: n = 101, ERBT: n = 101) were retained. There were no differences in perioperative outcomes between the two procedures. The 3-year RFS, PFS, and CSS were not different between the two procedures (p = 0.7, 1, and 0.7, respectively). Among patients who underwent repeat transurethral resection (reTUR), the rate of any residue on reTUR was significantly lower in the ERBT group (cTURBT: 36% versus ERBT: 15%, p = 0.029). Adequate sampling of muscularis propria (83% versus 93%, p = 0.029) and diagnostic rates of pT1a/b substaging (90% versus 100%, p < 0.001) were significantly better in ERBT specimen compared with cTURBT specimen. On multivariable analyses, pT1a/b substaging was a prognosticator of disease progression.

CONCLUSIONS

In patients with pT1HG bladder cancer, ERBT had similar perioperative and mid-term oncologic outcomes compared with cTURBT. However, ERBT improves the quality of resection and specimen, yielding less residue on reTUR and yielding superior histopathologic information such as substaging.

Combination of Two T1 Substaging Systems (T1a/b/c and T1m/e) Better Predicts Tumor Outcomes in Patients with T1 High Grade Bladder Cancer

BACKGROUND

T1 substaging is a predictive factor for non-muscle-invasive bladder cancer, and two types of T1 substaging systems (T1a/b/c and T1m/e) are currently in use. However, the predictive ability of both systems is poor, and there is debate over which system is better.

OBJECTIVE

To confirm whether combination of two T1 substaging systems can improve the predictive ability of T1 substaging for tumor outcomes.

METHODS

Patients with primary pT1 high-grade bladder cancer from three centers were included. All tumors were assessed with T1a/b/c and T1m/e substaging. A new variable named COMB was developed in which patients were stratified into T1a/b&T1m, T1a/b&T1e, T1c&T1m or T1c&T1e subgroups. A time-dependent receiver operating characteristic curve (ROC) analysis was used to test whether the accuracy of prediction could be improved with COMB.

RESULTS

A total of 239 patients with primary pT1HG were analyzed. No tumor was T1c&T1m, and therefore, only three types of combinations were evaluated: T1a/b&T1m (62 patients), T1a/b&T1e (124 patients) and T1c&T1e (53 patients). Regardless of all patients or those treated with Re-TURBt and adequate BCG, patients with T1a/b&T1m have the best prognosis, and those with T1c&T1e have the poorest prognosis. The time-dependent ROC showed that, for both recurrence and progression, COMB had a higher AUC than T1a/b/c and T1m/e, regardless of population.

CONCLUSIONS

Compared with either system alone, the combination of two T1 substaging systems improves the predictive ability of T1 substaging for tumor outcomes.

Urothelial Carcinoma: Divergent Differentiation and Morphologic Subtypes

Urothelial carcinoma (UC) is known to encompass a wide spectrum of morphologic features and molecular alterations. Approximately 15% to 25% of invasive UC exhibits histomorphologic features in the form of "divergent differentiation" along other epithelial lineages, or different "subtypes" of urothelial or sarcomatoid differentiation. It is recommended that the percentage of divergent differentiation and or subtype(s) be reported whenever possible. Recent advances in molecular biology have led to a better understanding of the molecular underpinning of these morphologic variations. In this review, we highlight histologic characteristics of the divergent differentiation and subtypes recognized by the latest version of WHO classification, with updates on their molecular and clinical features.

Clinical utility of histopathology data: urological cancers

Cancer datasets recommend standardised reporting of histopathological data items with elements categorised as either core (required) or non-core (recommended), irrespective of the clinical scenario. However, the clinical significance of a data item in an individual case would depend on the clinicopathological setting as well as local management guidelines. A data item that is critical for patient management in one clinical scenario may be largely irrelevant in another patient. Pathologists must understand how their data are used in clinical practice so that they can focus their limited resources appropriately. We briefly review the use of histopathological data in the management of urological cancers, highlighting scenarios where a data item may be of limited clinical utility.

The Influence of Oncogenic Viruses in Renal Carcinogenesis: Pros and Cons

Viral infections are major contributors to the global cancer burden. Recent advances have revealed that known oncogenic viruses promote carcinogenesis through shared host cell targets and pathways. The aim of this review is to point out the connection between several oncogenic viruses from the Polyomaviridae, Herpesviridae and Flaviviridae families and renal carcinogenesis, highlighting their involvement in the carcinogenic mechanism. We performed a systematic search of the PubMed and EMBASE databases, which was carried out for all the published studies on RCC in the last 10 years, using the following search algorithm: renal cell carcinoma (RCC) and urothelial carcinoma, and oncogenic viruses (BKPyV, EBV, HCV, HPV and Kaposi Sarcoma Virus), RCC and biomarkers, immunohistochemistry (IHC). Our analysis included studies that were published in English from the 1st of January 2012 to the 1st of May 2022 and that described and analyzed the assays used for the detection of oncogenic viruses in RCC and urothelial carcinoma. The virus most frequently associated with RCC was BKPyV. This review of the literature will help to understand the pathogenic mechanism of the main type of renal malignancy and whether the viral etiology can be confirmed, at a minimum, as a co-factor. In consequence, these data can contribute to the development of new therapeutic strategies. A virus-induced tumor could be efficiently prevented by vaccination or treatment with oncolytic viral therapy and/or by targeted therapy.

Nonmuscle-invasive bladder cancer, old problems, new insights

PURPOSE OF REVIEW

Nonmuscle-invasive bladder cancer (NMIBC) is the most frequent bladder cancer and represents around 75% of bladder cancers. This review will discuss known challenges and recent advances in staging, grading and treatment stratification based on pathology.

RECENT FINDINGS

Pathological staging and grading in NMIBC remains challenging and different techniques exist. Substaging has been shown to be of prognostic relevance and to help predict treatment response in patients receiving Bacillus Calmette-Guérin (BCG) therapy, which is the treatment of choice for high-grade NMIBC. Recent advances in molecular classification and artificial intelligence were also able to show promising results in the stratification of patients.

SUMMARY

Many challenges in the diagnosis of NMIBC are still unresolved and ask for more prospective research. New technologies, molecular insights and AI will help in the upcoming years to better stratify and manage these patients.

Clinicopathological Review of Micropapillary Urothelial Carcinoma

PURPOSE OF REVIEW

This review will discuss micropapillary urothelial carcinoma with respect to biology, histopathologic characteristics, genetic and molecular features, diagnosis, clinical management, and future directions of research.

RECENT FINDINGS

Recent consensus opinion study showed only moderate interobserver reproducibility in the diagnostic criteria. The most reproducible criteria with the highest consensus were multiple nests in the same lacunar spaces. There are recent reports of high rates of intratumoral heterogeneity of ERBB2 amplification within tumor containing both micropapillary and classic urothelial components. Micropapillary urothelial carcinoma is a well-documented highly aggressive variant of urothelial carcinoma with proven worse outcomes. Accurate recognition and reporting of this pattern is critical for optimal management. Newer therapeutic strategies related to the molecular and genetic findings seen in MPUC remain to be explored further.

Updated pathology reporting standards for bladder cancer: biopsies, transurethral resections and radical cystectomies

Aim

Optimal management of bladder cancer requires an accurate, standardised and timely pathological diagnosis, and close communication between surgeons and pathologists. Here, we provide an update on pathology reporting standards of transurethral resections of the bladder and cystectomies.

Methods

We reviewed recent literature, focusing on developments between 2013 and 2021.

Results

Published reporting standards developed by pathology organizations have improved diagnosis and treatment. Tumor sub-staging and subtyping has gained increased attention. Lymph nodes continue to be an area of debate, and their staging has seen minor modifications. Several tasks, particularly regarding specimen preparation (“grossing”), are not yet standardized and offer opportunity for improvement. Molecular classification is rapidly evolving, but currently has only limited impact on management.

Conclusion

Pathological reporting of bladder cancer is continuously evolving and remains challenging in some areas. This review provides an overview of recent major developments, with a particular focus on published reporting standards.