Micropapillary Bladder Cancer: Insights from the National Cancer Database

Early experience with sequential intravesical gemcitabine and docetaxel for micropapillary variant non-muscle invasive bladder cancer

BACKGROUND

Guidelines lack clear recommendations regarding conservative management of micropapillary (MP) variant non-muscle invasive bladder cancer (NMIBC). Bladder-sparing therapy using intravesical Bacillus Calmette-Guerin (BCG) has been reported although there are concerns regarding recurrence and progression with this approach. Due to the ongoing BCG shortage, we have utilized sequential intravesical gemcitabine and docetaxel (Gem/Doce) as primary therapy for NMIBC, including some cases with limited MP urothelial carcinoma (MPUC). To compare oncologic outcomes of patients with non-muscle invasive MPUC and conventional UC treated with Gem/Doce.

METHODS

A secondary analysis of 138 patients with high-risk NMIBC treated with intravesical Gem/Doce from January 2011 to December 2021 was performed. Oncologic outcomes were compared in patients with or without MPUC using the Kaplan-Meier method.

RESULTS

Median follow-up (f/u) for all patients was 23 months (IQR 13-34). There were 129 patients with pure UC and 9 with MPUC. In those with MPUC, all were high-grade (HG), 8/9 were stage T1, 7/9 had a focal MP component (extent < 10%), 3/9 had concomitant CIS, and 2/9 had lymphovascular invasion. All MPUC tumors were re-resected, and 4 had T0, 3 had T1 HG, 1 had Ta HG, 1 had carcinoma in situ (CIS); none had residual MP or LVI tumors before Gem/Doce treatment. The 24-month high-grade recurrence-free survival was 89% and 80% in patients with MPUC and pure UC, respectively. Survival outcomes did not significantly differ between patients with and without MPUC. Four patients with MPUC experienced recurrent NMIBC after Gem/Doce, and all were treated successfully with rescue sequential intravesical valrubicin and docetaxel (Val/Doce). Pathology of these four recurrent patients revealed more aggressive histologic features in the original tumor including: multifocal tumor (3/4), T1 HG disease (4/4), concomitant CIS (2/4), and moderate MP variant extent (30%) (1/4). No patient with MPUC underwent cystectomy, experienced progression, or died at last follow-up (median f/u of 43 months).

CONCLUSIONS

Gem/Doce with Val/Doce rescue appears to have activity against carefully selected non-muscle invasive MPUC with favorable histology. Larger prospective trials are needed to validate these results.

Learning generalizable AI models for multi-center histopathology image classification

Investigation of histopathology slides by pathologists is an indispensable component of the routine diagnosis of cancer. Artificial intelligence (AI) has the potential to enhance diagnostic accuracy, improve efficiency, and patient outcomes in clinical pathology. However, variations in tissue preparation, staining protocols, and histopathology slide digitization could result in over-fitting of deep learning models when trained on the data from only one center, thereby underscoring the necessity to generalize deep learning networks for multi-center use. Several techniques, including the use of grayscale images, color normalization techniques, and Adversarial Domain Adaptation (ADA) have been suggested to generalize deep learning algorithms, but there are limitations to their effectiveness and discriminability. Convolutional Neural Networks (CNNs) exhibit higher sensitivity to variations in the amplitude spectrum, whereas humans predominantly rely on phase-related components for object recognition. As such, we propose Adversarial fourIer-based Domain Adaptation (AIDA) which applies the advantages of a Fourier transform in adversarial domain adaptation. We conducted a comprehensive examination of subtype classification tasks in four cancers, incorporating cases from multiple medical centers. Specifically, the datasets included multi-center data for 1113 ovarian cancer cases, 247 pleural cancer cases, 422 bladder cancer cases, and 482 breast cancer cases. Our proposed approach significantly improved performance, achieving superior classification results in the target domain, surpassing the baseline, color augmentation and normalization techniques, and ADA. Furthermore, extensive pathologist reviews suggested that our proposed approach, AIDA, successfully identifies known histotype-specific features. This superior performance highlights AIDA's potential in addressing generalization challenges in deep learning models for multi-center histopathology datasets.

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.

The role of neoadjuvant chemotherapy for patients with variant histology muscle invasive bladder cancer undergoing robotic cystectomy: Data from the International Robotic Cystectomy Consortium

OBJECTIVE

To assess the role of neoadjuvant chemotherapy (NAC) before robot-assisted radical cystectomy (RARC) for patients with variant histology (VH) muscle-invasive bladder cancer (MIBC).

METHODS

Retrospective review of 988 patients who underwent RARC (2004-2023) for MIBC. Primary outcomes included the utilization of NAC among this cohort of patients, frequency of downstaging, and discordance between preoperative and final pathology in terms of the presence of VH. Secondary outcomes included disease-specific (DSS), recurrence-free (RFS), and overall survival (OS).

RESULTS

A total of 349 (35%) had VH on transurethral resection or at RARC. The 4 most common VH subgroups were squamous (n = 94), adenocarcinoma (n = 64), micropapillary (n = 34), and sarcomatoid (n = 21). There was no difference in OS (log-rank: P = 0.43 for adenocarcinoma, P = 0.12 for micropapillary, P = 0.55 for sarcomatoid, P = 0.29 for squamous), RFS (log-rank: P = 0.25 for adenocarcinoma, P = 0.35 for micropapillary, P = 0.83 for sarcomatoid, P = 0.79 for squamous), or DSS (log-rank P = 0.91 for adenocarcinoma, P = 0.15 for micropapillary, 0.28 for sarcomatoid, P = 0.92 for squamous) among any of the VH based on receipt of NAC. Patients with squamous histology who received NAC were more likely to be downstaged on final pathology compared to those who did not (P < 0.01).

CONCLUSION

Our data showed no significant difference in OS, RFS, or DSS for patients with VH MIBC cancer who received NAC before RARC. Patients with the squamous variant who received NAC had more pathologic downstaging compared to those who did not. The role of NAC among patients with VH is yet to be defined. Results were limited by small number in each individual group and lack of exact proportion of VH.

Impact of variant histology on upstaging and survival in patients with nonmuscle invasive bladder cancer undergoing radical cystectomy

INTRODUCTION

Variant histology (VH) of urothelial carcinoma is uncommon and frequently presents at the muscle-invasive stage. VH is considering a significant risk factor for progression among patients with nonmuscle invasive bladder cancer (NMIBC). While there is some debate, expert opinion is generally that upfront radical cystectomy (RC) should be consider for these patients. Limited data exists to support this position. In this study, we sought to examine the rate of upstaging and overall survival for patients with VH NMIBC against patients with pure urothelial NMIBC who underwent RC, to help clarify the optimal treatment strategy for these patients.

METHODS

The institutional REDCap database was utilized to identify all patients with T1 and Ta bladder cancer that underwent RC over the study period (2004-2022). Matched-pair analysis was performed between patients with VH and pure urothelial NMIBC; 42 pairs were matched on prior intravesical therapy, presence of muscularis propria on transurethral resection of bladder tumor (TURBT), any carcinoma in situ presence on prior TURBTs, and final tumor staging on TURBT. The primary outcomes of interest were pathologic tumor upstaging rate at RC and overall survival. Secondary outcomes of interest included association of demographic or pretreatment variables with upstaging, and upstaging rates for specific variant histologies.

RESULTS

Patients with VH NMIBC undergoing RC were upstaged at a significantly higher rate than a matched cohort of patients with pure urothelial NMIBC (73.8% vs. 52.4%, P = 0.0244) and among those upstaged, had significantly higher rates of pT3 to pT4 (54.7% vs. 23.8%, P = 0.0088). Rate of node positivity at RC for VH NMIBC was also higher compared to pure urothelial NMIBC (40.5% vs. 21.4%, P = 0.0389). Among histologic variants, patients with plasmacytoid and sarcomatoid subtypes demonstrated the highest rates of upstaging; differences were not statistically significant. The overall median survival was 28.4 months for patients with VH after RC compared to 155.1 months for patients with pure urothelial NMIBC (P = 0.009).

CONCLUSION

Patients with VH NMIBC undergoing RC are at significantly higher risk of upstaging at RC when compared to patients with pure urothelial NMIBC and have worse overall survival. While this study supports the concept of an aggressive treatment approach for patients with VH NMIBC, improvements in understanding of the disease are necessary to improve outcomes.

Predictors of response to neoadjuvant therapy in urothelial cancer

Neoadjuvant cisplatin-based chemotherapy (NACC) followed by radical cystectomy is the standard treatment for localized muscle-invasive bladder cancer (MIBC). Patients who achieve a complete pathological response following NACC have better overall survival than those with residual disease. However, a subset of patients does not derive benefit from NACC while experiencing chemotherapy-related side effects that may delay cystectomy, which can be detrimental. There is a need for predictive and prognostic biomarkers to better stratify patients who will derive benefits from NACC. This review summarizes the currently available literature on various predictors of response to neoadjuvant chemotherapy. Covered predictors include clinical factors, treatment regimens (including chemotherapy and immunotherapy), histological predictors, and molecular predictors such as DNA repair genes, p53, FGFR3, ERBB2, Bcl-2, EMMPRIN, survivin, choline-phosphate cytidylyltransferase-α, epigenetic markers, immunological markers, other molecular predictors and gene expression profiling. Further, we elaborate on the potential role of neoadjuvant immunotherapy and the correlative biomarkers of response.

Neoadjuvant Chemotherapy Prior to Radical Cystectomy for Muscle-Invasive Bladder Cancer With Variant Histology: A Systematic Review and Meta-Analysis of Survival Outcomes and Pathological Features

PURPOSE

To conduct systematic review and meta-analysis to evaluate effects of neoadjuvant chemotherapy (NAC) on survival and histopathological outcomes of variant histology (VH) of urothelial carcinoma (UC) of bladder.

METHODS

This systematic review was registered in PROSPERO (CRD42023389115). Literature search was conducted in PubMed/Medline, Embase, and Cochrane Library for studies published up to January 2023. Population, intervention, comparator, outcome, and study design were as follows: bladder cancer patients with VH (population), neoadjuvant chemotherapy (intervention), radical cystectomy only (comparators), oncological survival and pathologic response (outcomes), and retrospective or prospective (study design).

RESULTS

Finally, a total of 17 studies were included in the present study (quantitative analysis, n = 17; qualitative analysis, n = 12). Pooled HR was 0.49 (95% CI: 0.31-0.76; P = .002) for OS. Pooled HR was 0.61 (95% CI: 0.38-0.98; P = .04) for CSS. Pooled HR was 0.44 (95% CI: 0.21-0.93; P = .03) in PFS. Pooled OR was 6.61 (95% CI: 4.50-9.73; P < .00001) in complete pathologic response. Pooled OR was 9.59 (95% CI: 3.56-25.85; P < .00001) in any pathologic response. Evidence quality assessments for each 5 comparisons using the GRADE approach were that Certainty was moderate in 1, low in 1, and very low in 3.

CONCLUSIONS

Administration of NAC before surgery in bladder cancer patients with VH might confer better survival outcomes and higher pathologic down staging rate than no administration of NAC before surgery.

International Society of Urological Pathology (ISUP) Consensus Conference on Current Issues in Bladder Cancer. Working Group 2: Grading of Mixed Grade, Invasive Urothelial Carcinoma Including Histologic Subtypes and Divergent Differentiations, and Non-Urothelial Carcinomas

The 2022 International Society of Urological Pathology (ISUP) Consensus Conference on Urinary Bladder Cancer Working Group 2 was tasked to provide evidence-based proposals on the applications of grading in noninvasive urothelial carcinoma with mixed grades, invasive urothelial carcinoma including subtypes (variants) and divergent differentiations, and in pure non-urothelial carcinomas. Studies suggested that predominantly low-grade noninvasive papillary urothelial carcinoma with focal high-grade component has intermediate outcome between low- and high-grade tumors. However, no consensus was reached on how to define a focal high-grade component. By 2004 WHO grading, the vast majority of lamina propria-invasive (T1) urothelial carcinomas are high-grade, and the rare invasive low-grade tumors show only limited superficial invasion. While by 1973 WHO grading, the vast majority of T1 urothelial carcinomas are G2 and G3 and show significant differences in outcome based on tumor grade. No consensus was reached if T1 tumors should be graded either by the 2004 WHO system or by the 1973 WHO system. Because of the concern for underdiagnosis and underreporting with potential undertreatment, participants unanimously recommended that the presence of urothelial carcinoma subtypes and divergent differentiations should be reported. There was consensus that the extent of these subtypes and divergent differentiations should also be documented in biopsy, transurethral resection, and cystectomy specimens. Any distinct subtype and divergent differentiation should be diagnosed without a threshold cutoff, and each type should be enumerated in tumors with combined morphologies. The participants agreed that all subtypes and divergent differentiations should be considered high-grade according to the 2004 WHO grading system. However, participants strongly acknowledged that subtypes and divergent differentiations should not be considered as a homogenous group in terms of behavior. Thus, future studies should focus on individual subtypes and divergent differentiations rather than lumping these different entities into a single clinicopathological group. Likewise, clinical recommendations should pay attention to the potential heterogeneity of subtypes and divergent differentiations in terms of behavior and response to therapy. There was consensus that invasive pure squamous cell carcinoma and pure adenocarcinoma of the bladder should be graded according to the degree of differentiation. In conclusion, this summary of the International Society of Urological Pathology Working Group 2 proceedings addresses some of the issues on grading beyond its traditional application, including for papillary urothelial carcinomas with mixed grades and with invasive components. Reporting of subtypes and divergent differentiation is also addressed in detail, acknowledging their role in risk stratification. This report could serve as a guide for best practices and may advise future research and proposals on the prognostication of these tumors.

The Many Faces of Urothelial Carcinomas: An Update From Pathology to Clinical Approach and Challenges in Practice

Urothelial carcinoma is a heterogeneous disease with histomorphological and genomic variations throughout the same tumor or between tumors from different patients. It has been shown that most of these histologic and genetic differences have prognostic significance and may have a guiding role in determining the appropriate treatment choice for the patient. Therefore, it is crucial for both the pathologist and the clinician to be conscious of these variations and to consider them in patient management. Recently, a consensus molecular classification has been developed and categorized urothelial carcinomas into 6 subclasses. These molecular subclasses seem to be associated with prognosis and/or response to certain therapeutic approaches like chemotherapy or immune checkpoint inhibitory therapy; however, it has not yet been sufficiently validated and has some limitations for routine application. As is well known, there are therapeutic limitations in locally advanced or metastatic urothelial carcinomas, especially those inappropriate for standard therapy with platinum-based chemotherapy regimens. Emerging new therapeutic approaches and testing for appropriate patient selection for those are discussed in this article.

Invasive Micropapillary Urothelial Carcinoma: an Uncommon and Underreported Variant in Cystectomy Specimens

Conventional urothelial carcinoma is the most common histological type of urinary bladder carcinoma. The latest edition of the WHO classification of tumours of the urothelial tract lays special emphasis on the ability of urothelial tumours to exhibit divergent differentiation with multiple histologic variants and a diverse genomic landscape. The presence of a micropapillary component (MPC) in urothelial carcinoma is associated with high-grade disease and poor response to intravesical chemotherapy. The present study aims to enumerate the clinicohistological features of urothelial carcinomas with micropapillary differentiation. Slides from 144 radical cystectomy specimens received over 6 years were reviewed independently by two pathologists. A predominant histological pattern along with co-existing pathology was noted. Of these, five cases were pure micropapillary carcinomas, four had conventional urothelial carcinoma with a MPC, one had a microscopic tumour at the mucosal surface, and two cases showed micropapillary histology in the lymph node metastasis, following transurethral resection of bladder tumour and Bacillus Calmette-Guerin therapy. The tumours with pure micropapillary carcinoma presented with a higher pathological stage and poor overall survival. Organ and lymph node metastasis was noted in five and eight cases, respectively, of which six showed a micropapillary pattern in the lymph nodes. Micropapillary urothelial carcinoma is a rare and aggressive variant of urothelial carcinoma with unique histologic features. This variant is often missed and underreported in biopsy and surgical resection specimens. Since the presence of MPC confers a poorer prognosis, the identification and reporting of this entity are important.

Nomograms for predicting survival in patients with micropapillary bladder cancer: a real-world analysis based on the surveillance, epidemiology, and end results database and external validation in a tertiary center

BACKGROUND

The present study aimed to construct and validate nomograms that can be used to predict cancer-specific survival (CSS) and overall survival (OS) in patients with micropapillary bladder cancer.

METHODS

The data of 627 patients diagnosed with micropapillary bladder cancer between 2000 and 2018 were obtained from the surveillance, epidemiology, and end results database. Patients were randomly divided into the training and internal validation sets (7:3). The Cox proportional hazards regression model was applied to evaluate the association between variables and survival and then nomograms were constructed to predict the survival of an individual patient. The performance of nomograms was validated by using calibration curves, concordance index, receiver operating characteristic curves with the calculated area under the curve and decision curve analysis in the training and internal validation set. Data from 41 micropapillary bladder cancer patients at Qilu Hospital of Shandong University from 2000 to 2022 were collected for external validation.

RESULTS

Several independent risk factors were taken into the two nomograms (CSS and OS), including age, marital status, AJCC TMN stage, surgical approach, lymph node ratio, and tumor size while the OS nomogram additionally contained race. The concordance index of the training set, internal validation set, and external verification set were all over 0.7. The calibration curve indicated good consistence between the nomogram prediction and actual survival. Area under the curve and decision curve analysis results indicated great clinical usefulness of nomograms.

CONCLUSIONS

The nomograms predicting the survival outcome of patients with micropapillary bladder cancer would provide a valuable tool to help clinicians to evaluate the risk of patients and make individual treatment strategies.

Oncologic outcomes of neoadjuvant chemotherapy in patients with micropapillary variant urothelial carcinoma of the bladder

BACKGROUND

There is lack of consensus about the effectiveness of neoadjuvant platinum-based chemotherapy in patients with micropapillary variant urothelial carcinoma (MVUC) prior to radical cystectomy. We studied the association between neoadjuvant chemotherapy (NAC) and pathologic response (PR) among patients with micropapillary versus non-variant bladder urothelial carcinoma (UC).

METHODS

We queried the National Cancer Database to identify patients with localized UC and MVUC from 2004 to 2017. We restricted our analysis to patients who underwent radical cystectomy with or without NAC. We compared clinical, demographic, and pathologic characteristics associated with NAC. We used multivariable logistic regression and propensity score matching to examine the association between NAC and the occurrence of a pathologic complete response (pT0) and pathologic lymph node positivity (pN+). Kaplan Meier analyses and Cox proportional hazards models were used to assess overall survival (OS). We performed analyses among subsets of patients with clinical stage II (cT2) disease, as well as the entire cohort (cT2-T4).

RESULTS

We identified 18,761 patients, including 18,027 with non-variant UC and 734 patients with MVUC. Multivariable analysis revealed that NAC use was associated with greater odds of pT0 (9.64[7.62-12.82], P<0.001), and the association did not differ significantly between MVUC and non-variant UC. In a propensity matched analysis of patients with MVUC, NAC use was associated with higher odds of pT0 (OR 4.93 [2.43-13.18] P<0.001), lower odds of pN+ (OR 0.52 [0.26-0.92] P=0.047) and pathologic upstaging (OR 0.63 [0.34-0.97] P=0.042) in all stages. Similar findings were observed with cT2 disease. No significant association was seen between NAC and OS with MVUC (HR 0.89 [0.46-1.10] P=0.63), including the subset of patients with cT2 (HR 0.83 [0.49-1.06] P=0.58).

CONCLUSIONS

NAC is associated with similar pathologic and nodal responses in patients with localized MVUC and non-variant UC. Improvements in pathologic findings did not translate into OS in this retrospective hospital-based registry study.

Bladder Preservation for Muscle-Invasive Bladder Cancer With Variant Histology

A growing body of evidence has shown bladder-preservation with chemo-radiotherapy achieves comparable survival to Radical Cystectomy (5-year OS 50%-70%) and superior quality of life outcomes for patients with muscle-invasive urothelial carcinoma of the bladder (UC). However, up to 55% of patients harbor variant histology and in this review we aim to clarify the role of bladder-preservation for this group. We first draw the distinction between urothelial carcinoma with divergent differentiation (UCDD) and non-urothelial carcinoma (NUC). UCDD is common, increasing in prevalence, and whilst each subtype may have its own characteristics current evidence suggests comparable outcomes with radical cystectomy and bladder-preservation. Non-urothelial carcinoma is a collection of distinct pathologies each deserving of its own management strategy. However, these tumors are rare, and evidence is generated from retrospective studies with significant inherent bias. Small cell carcinoma of the bladder has good evidence for bladder-preservation; however, other pathologies such as Squamous Cell Carcinoma and Adenocarcinoma are not well supported. We recommend careful multidisciplinary appraisal of the evidence for each subtype and honest patient discussion about the limited evidence before reaching management decisions. As we look to the future molecular-profiling may help better characterize these tumors and aid in treatment selection.

Urothelial Carcinoma: Update on Staging and Reporting, and Pathologic Changes Following Neoadjuvant Chemotherapies

Staging and reporting of cancers of the urinary tract have undergone major changes in the past decade to meet the needs for improved patient management. Substantial progress has been made. There, however, remain issues that require further clarity, including the substaging of pT1 tumors, grading and reporting of tumors with grade heterogeneity, and following NAC. Multi-institutional collaborative studies with prospective data will further inform the accurate diagnosis, staging, and reporting of these tumors, and in conjunction with genomic data will ultimately contribute to precision and personalized patient management.

Radical cystectomy for bladder urothelial carcinoma with aggressive variant histology

Purpose: The aim of this study is to report our experience in managing bladder cancer in patients with variant pathology. Methods: Retrospective data collection for all patients managed by radical cystectomy over the last 3 years for a variant pathol-ogy was completed. We specifically included micropapillary and nested variants. Results: Ten patients were identified, with eight having micropapillary carcinoma (MPC) and two having nested vari-ants. Nine patients were male. The median age was 75. The two patients with nested variant were 56 and 62 years old, respec-tively, whereas all patients with MPC were over the age of 70. Upon cystectomy of all micropapillary cases, three patients(37.5%) had positive lymph node invasion and the final patholo-gy was T2 (two patients), T3 (two patients), and T4 (four patients). Barring a grade III complication Clavien-Dindo classi-fication due to wound dehiscence that necessitated secondary surgical closure, there were no specific perioperative complica-tions. Given the urethral invasion, cystourethrectomy was per-formed on the female patient. Within a median 13-month fol-low-up, three patients developed local recurrence, including two urethral and one new lateral pelvic mass. Conclusions: Considering the muscle invasive nature of micropapillary and nested bladder cancer, aggressive surgical management should not be postponed. Moreover, due to notable prevalence of concurrent and/or recurrent urethral involvement, initial urethrectomy or early and frequent postoperative ure-throscopy should be provided. Patients with variant histology bladder cancer may benefit from early radical cystectomy when compared to bladder sparing protocols and prostate sparing cystectomy treatment options. 

Neoadjuvant chemotherapy for muscle-invasive bladder cancer: does variant histology matter?

PURPOSE

The most frequent histology of bladder tumors is urothelial carcinoma. Most are pure urothelial carcinomas (PUC) but up to one-third of the cases present variant histological (VH) features. The aim of this study was to evaluate the role of variant histology in neoadjuvant chemotherapy (NAC) response in patients with urothelial muscle-invasive bladder cancer.

METHODS

We retrospectively analyzed data from 77 patients with bladder cancer who performed neoadjuvant chemotherapy at two institutions.

RESULTS

Complete pathological response (ypT0) was higher in patients with PUC (38.5%), comparing with VH (12%). Logistic regression analysis demonstrated that variant histology is associated with an 89% lesser likelihood of tumor downstaging, with advanced clinical T stages and positive smoking history as independent predictors. The estimated mean cancer-specific survival was 68.91 months for PUC patients and 50.23 months for VH patients (log rank test, P = 0.024). Multivariate Cox regression analysis demonstrated that VH and clinical T stage were independent predictors of cancer-specific survival, indicating a worse outcome for patients with VH and advanced clinical T stages.

CONCLUSIONS

There are only a few retrospective studies evaluating the clinical impact of variant histology tumors, which are mainly managed as PUC. Our results demonstrate that VH is associated with a worse likelihood of tumor downstaging after NAC and a worse cancer-specific survival in bladder cancer patients. There is a need for further studies and genetic analysis to identify the patients most likely to achieve ypT0 status and downstaging after NAC.

Micropapillary bladder cancer: an evolving biology

PURPOSE OF REVIEW

To summarize a comprehensive overview of more recent evidence on micropapillary bladder cancer (MPBC), focusing on actual incidence, clinical features, therapeutic strategies, and prognosis.

RECENT FINDINGS

MPBC generally exhibits an aggressive behaviour compared with pure urothelial carcinoma (pUC) with advances in tumour stage and nodal and distant spread at diagnosis. Due to its rarity and presence of only small sample size and retrospective studies, no consensus currently exists regarding the most effective therapeutic strategy to be performed among nonmuscle-invasive (conservative treatment versus immediate radical cystectomy) and muscle-invasive MPBC (neoadjuvant therapy versus upfront radical cystectomy versus adjuvant chemotherapy).

SUMMARY

The incidence of MPBC is recently increased according to latter literature, ranging from 2.9 to 7.6% of all bladder cancer. Despite its aggressive behaviour at time of presentation, more recent evidence fails to demonstrate a significant association between MPBC and worse outcomes compared with pUC when adjusted for clinical and pathological features. According to latter evidence, MPBC pathological response to NAC appears to be unsatisfactory compared with pUC patients while neoadjuvant immunotherapy with Pembrolizumab may represent an effective treatment among MPBC patients, based on PD-L1 and TMB expression.

Neoadjuvant and Adjuvant Chemotherapy for Variant Histology Bladder Cancers: A Systematic Review and Meta-Analysis

Context

To improve the prognosis of variant histology (VH) bladder cancers, clinicians have used neoadjuvant chemotherapy (NAC) or adjuvant chemotherapy (AC) on the basis of radical cystectomy (RC). Despite some new data, the evidence remains mixed on their efficacy.

Objective

To update the current evidence on the role of NAC and AC for VH bladder cancers.

Evidence Acquisition

We searched for all studies investigating NAC or AC for bladder cancer patients with variant histology in PubMed, Embase, and the Cochrane Central Register of Controlled Trials up to December 2021. The primary end points were recurrence-free survival (RFS), cancer-specific survival (CSS), and overall survival (OS).

Evidence Synthesis

We identified 18 reports comprising a total of 10,192 patients in the NAC studies. In patients with VH, the use of NAC did improve CSS (hazard ratio [HR] 0.74, 95% confidence interval [CI] 0.55–0.99, p = 0.044), and OS (HR 0.74, 95% CI 0.66–0.84, p = 0.000), but not RFS (HR 1.15, 95% CI 0.56–2.33, p = 0.706). Subgroup analyses demonstrated that receiving NAC was associated with better OS in sarcomatoid VH (HR 0.67, 95% CI 0.54–0.83, p = 0.000) and neuroendocrine VH (HR 0.54, 95% CI 0.43–0.68, p = 0.000). For AC, we identified eight reports comprising a total of 3254 patients. There was a benefit in CSS (HR 0.61, 95% CI 0.43–0.87, p = 0.006) and OS (HR 0.76, 95% CI 0.60–0.98, p = 0.032). Subgroup analyses demonstrated that only neuroendocrine VH had better CSS (HR 0.29, 95% CI 0.13–0.67, p = 0.174) when receiving AC.

Conclusions

NAC or AC for VH bladder cancers confers an OS and CSS benefit compared with RC alone. For NAC, the benefit was independently observed in the sarcomatoid and neuroendocrine subgroups. As for AC, only neuroendocrine subgroups improved CSS.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42021289487.

Cytologic features of micropapillary variant urothelial carcinoma in urinary tract cytology: Case series and review of literature

BACKGROUND

The micropapillary variant of urothelial carcinoma (MPVUC) is rare and aggressive. Surgical specimens often show atypical micro-clusters (AMCs) of cells with hyperchromatic, pyknotic, peripheral, irregular nuclei with variable nuclear to cytoplasmic ratios. We reviewed urinary tract cytology (UTC) from patients with MPVUC and hypothesized that AMCs would be present similar to those in surgical specimens.

METHODS

The archives were searched from 2000 to 2020 for patients with surgical cases with either MPVUC or conventional high-grade urothelial carcinoma (HGUC) and with prior abnormal UTC. Two pathologists reviewed UTC cases and controls in a blinded manner for AMCs, with quantitation of none, low, moderate, and high. Interrater reliability was compared by quadratic weighted Cohen's Kappa test. The association between numerical average score and MPVUC status was determined by logistic regression.

RESULTS

Five patients with invasive MPVUC, one patient with a noninvasive micropapillary component, and 15 control patients with conventional HGUC were included. All patients had prior or concurrent abnormal UTC samples. Increasing category of quantities of AMCs on cytology was associated with micropapillary status (OR 7.9, 95% CI 2.7-118, p = .045), with moderate agreement between raters (Cohen's Kappa 0.54, 95% CI 0.19-0.89, p = .004).

CONCLUSIONS

In patients with MPVUC on surgical specimen, AMCs were frequently observed on cytology. Similar atypical clusters were observed in patients with nonmicropapillary HGUC, albeit at lower frequency. However, given the WHO recommendation to diagnose micropapillary only if an invasive micropapillary component is present, a specific diagnosis of MPVUC on UTC cannot be based solely on the presence of AMCs.

Micropapillary bladder cancer: an added indication to prophylactic urethrectomy

There is little research on the role of urethrectomy during cystectomy in patients with micropapillary bladder cancer (MPBC). We present two cases of MPBC cystectomy and suggest that urethrectomy be performed concurrently as a preventive measure. The first case involved a woman who had a mixed solid and papillary bladder tumour. An anterior pelvic exenteration was performed as well as a total urethrectomy. The T4a micropapillary variant tumour was confirmed by pathology. The second case involved a man with T1 MPBC who was treated with a BCG induction course. A recurrent muscle-invasive MPBC was discovered during follow-up. During the radical cystoprostatectomy, the urethra was spared. T2 MPBC was discovered through pathology. He had a urethrectomy 6 months later due to urethral bleeding, and the pathology revealed micropapillary cancer of the urethra.

The effect of neoadjuvant chemotherapy among patients undergoing radical cystectomy for variant histology bladder cancer: A systematic review

Objective

To systematically review the evidence about the effect of neoadjuvant chemotherapy (NAC) for muscle-invasive bladder cancer (MIBC) with pure urothelial carcinoma (pUC) in radical cystectomy (RC) candidates affected by variant histology (VH) bladder cancer.

Methods

A review of the current literature was conducted through the Medline and National Center for Biotechnology Information (NCBI) PubMed, Scopus databases in May 2020. The updated Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed for this systematic review. Keywords used were ‘bladder cancer’, ‘bladder carcinoma’, ‘bladder tumour’ and ‘bladder cancer variants’ and ‘neoadjuvant chemotherapy’. Only original articles in English published after 2000 and reporting oncological outcomes a series of more than five patients with VH were included. We excluded series in which the oncological outcomes of patients with pUC and VH were undistinguishable.

Results

The literature search identified 2231 articles. A total of 51 full-text articles were assessed for eligibility, with 17 eventually considered for systematic review, for a cohort of 450,367 patients, of which 5010 underwent NAC + RC. The median age at initial diagnosis ranged from 61 to 71 years. Most patients received cisplatin-gemcitabine, methotrexate-vinblastine-adriamycin-cisplatin, or carboplatin-based chemotherapy. Only one study reported results of neoadjuvant immunotherapy. The median follow-up ranged from 1 to 120 months. The results showed that squamous cell carcinoma (SCC) is less sensitive to NAC than pUC and that SCC predicts poorer prognosis. NAC was found to be a valid approach in treating small cell carcinoma and may have potential benefit in micropapillary carcinoma.

Conclusions

NAC showed the best oncological outcomes in small cell variants and micropapillary carcinoma, while NAC survival benefit for SCC and adenocarcinoma variants needs further studies. Drawing definite considerations on the efficacy of NAC in VH is complicated due to the heterogeneity of present literature. Present results need to be confirmed in randomised controlled trials.

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.

Non-Muscle Invasive Bladder Cancer with Variant Histology: Biological Features and Clinical Implications

BACKGROUND

The most common bladder cancer (BC) histotype is pure urothelial carcinoma (UC), which may undergo divergent differentiation in some cases. Variant histology (VH) presents along variable morphologies, either single or combined between them or with pure UC. From a clinical standpoint, the vast majority of BC is diagnosed at non-invasive or minimally invasive stages, namely as non-muscle invasive BC (NMIBC). There is a wide range of therapeutic options for patients with NMIBC, according to their clinical and pathological features. However, current risk stratification models do not show optimal effectiveness. Evidence from the literature suggests that VH has peculiar biological features, and may be associated with poorer survival outcomes compared to pure UC.

SUMMARY

In order to describe the biological features and prognostic/predictive role of VH in NMIBC, and to discuss current treatment options, we performed a systematic literature search through multiple databases (PubMed/Medline, Google Scholar) for relevant articles according to the following terms, single and/or in combination: "non-muscle invasive bladder cancer," "variant histology," "micropapillary variant," "glandular differentiation," "squamous differentiation," "nested variant," "plasmacytoid variant," and "sarcomatoid variant." We extracted 99 studies including original articles, reviews, and systematic reviews, and subsequently analyzed data from 16 studies reporting on the outcome of NMIBC with VH. We found that the relative rarity of these forms as well as the heterogeneity in study populations and therapeutic protocols results in conflicting findings overall. Key Messages: The presence of VH should be taken into account when counseling a patient with NMIBC, since it may upgrade the disease to high-risk tumor and thus warrant a more aggressive treatment.

The optimal management of variant histology in muscle invasive bladder cancer

Bladder cancer is a heterogenous disease that is associated with tangible mortality in muscle invasive disease. The WHO 2016 classification of urothelial tumours reflects the contemporary approach towards histological variants in bladder cancer, including variants of urothelial carcinoma (UC) and non-urothelial variants. This review focuses on variant histology in UC, and discusses the importance of accurate histological diagnosis, and subsequent risk stratification and therapeutic decision making based on proper variant recognition. Most urothelial variants are associated with poorer outcomes compared to conventional UC, although some perform reasonably better. However, high quality evidence detailing optimal treatment and survival outcomes are still lacking in literature, due to the rarity of these cases.

Transcriptomic analysis of micropapillary high grade T1 urothelial bladder cancer

No consensus currently exist on the optimal treatment of patients with high-risk nonmuscle invasive (HGT1) micropapillary variant of bladder cancer (MPBC). Transcripsome analysis may allow stratification of MPBC-HGT1 enabling prediction of recurrence and guide therapeutic management for individual patients. Whole transcriptome RNA-Sequencing of tumors from 23 patients with MPBC-HGT1 and 64 conventional urothelial carcinomas (cUC) (reference set) was performed. Differentially expressed genes between MPBC-HGT1 and cUC-HGT1 were explored. Cox proportional hazard models and Kapplan–Meier methods were used to assess the relation between time to progression (TTP) and individual gene expression adjusting for clinical covariates. Over 3000 genes were differentially expressed in MPBC-HGT1 as compared with cUC-HGT1 and a 26-gene signature is characteristic of MPBC within HGT1. A set of three genes; CD36, FAPB3 and RAETE1; were significantly associated with TTP. High expression of FABP3 and CD36 were associated with shorter TTP (p = 0.045 and p = 0.08) as was low expression of RAET1E (p = 0.01). Our study suggest that a 26-gene signature can define MPBC-HGT1 within conventional urothelial carcinomas. A prognostic risk index of three genes (FABP3, CD36 and RAET1E) was found to be associated with shorter TTP and may help classify a group of patients with MPBC-HGT1 with high-risk of early progression. These observations might have implications in terms of radical cystectomy recommendation in MPBC patients.

Clinical Characteristics and Prognosis of Rare Histological Variants of Bladder Cancer: A Single-Center Retrospective Study from China

Objective

To investigate the clinical characteristics and prognosis of patients with rare histological variants of bladder cancer (RHV-BC) in China.

Materials and Methods

Patients diagnosed as bladder carcinoma with RHV in our center, from March 2009 and April 2019, were included. The univariate and multivariate COX regression model were used to evaluate the association between clinical characteristics and overall survival (OS).

Results

A total of 54 (1.4%) patients with RVH-BC were identified from 3803 potential patients with bladder cancer. The RHV classifications included micropapillary variant (MPV), sarcomatoid variant (SAV), neuroendocrine variant (NEV), nested variant (NV), plasmacytoid variant (PCV), and lymphoepithelioma-like variant (LEV), which were found in 19, 18, seven, six, three, and one patient, respectively. The mean of recurrence-free survival (RFS), cancer-specific survival (CSS), and OS of patients were 18.8 months, 37.0 months and 36.0 months, respectively. The multivariable analyses indicated that metastasis and T ≥2 were independent risk factors of OS. Besides, 84.4% (27/32) of patients who were receiving intravesical therapies (IVT) suffered recurrence. Patients with adjuvant chemotherapy (AC) had a recurrence rate of 64.7% (11/17).

Conclusion

T≥2 and metastasis were independent risk factors of OS in patients with RHV-BC. Considering a high recurrence following transurethral resection of bladder tumor (TURBT) and IVT, early radical cystectomy (RC) might be performed for patients with RHV-BC.

Urothelial carcinoma: variant histology, molecular subtyping, and immunophenotyping significant for treatment outcomes

Although urothelial carcinoma (UC) has been recognised as a homogenous disease entity until recently, it exhibits widely diverse histological variants. Recent studies have revealed that some histological variants may serve as markers of very high risk for advanced cancers and poor prognoses. Certain histological variants can generate a pathological T stage, which may result in unnecessary surgery. Though platinum based chemotherapy is the standard treatment, the use of immune checkpoint inhibitors (ICIs) for UC treatment has become a major trend in oncology. UCs showing specific histological variants have responded exceptionally well to chemotherapy and ICIs. Currently, molecular studies base molecular classification on gene expression profile signatures in order to make diagnoses or predict responses to chemotherapies and ICIs. Notably, some histological variants correlate with specific molecular subtypes. The usefulness of immunophenotyping for classification purposes was recognised only recently. Immunophenotypes are classified into three categories according to lymphocyte distribution in or around the cancer cell nest: desert, excluded, and inflamed. This immunophenotyping has been increasingly shown to be of value in predicting the response to ICIs. This review describes the morphological characteristics of histological variants as well as the advantages and limitations in determining them, with particular reference to clinical benefits. Subsequently, we describe the concept of molecular classification and immunophenotypes, and their morphological features, which are easily interpreted and amenable to daily practice via hematoxylin and eosin staining. We also consider the clinical advantages, limitations, and issues encountered while using these in routine clinical practice.

Response to Neoadjuvant Chemotherapy and Survival in Micropapillary Urothelial Carcinoma: Data From a Tertiary Referral Center and the Surveillance, Epidemiology, and End Results (SEER) Program

BACKGROUND

Micropapillary urothelial carcinoma (MPC) is a rare urothelial carcinoma variant with conflicting data guiding clinical practice. In this study, we explored oncologic outcomes in relation to neoadjuvant chemotherapy (NAC) in a retrospective cohort of patients with MPC, alongside data from Surveillance, Epidemiology, and End Results (SEER)-Medicare.

PATIENTS AND METHODS

We retrospectively identified patients with MPC or conventional urothelial carcinoma (CUC) without any variant histology undergoing radical cystectomy (RC) in our institution (2003-2018). SEER-Medicare was also queried to identify patients diagnosed with MPC (2004-2015). Clinicopathologic data and treatment modalities were extracted. Overall survival (OS) was estimated with the Kaplan-Meier method. Mann-Whitney-Wilcoxon and chi-square tests were used for comparative analysis and Cox regression for identifying clinical covariates associated with OS.

RESULTS

Our institutional database yielded 46 patients with MPC and 457 with CUC. In SEER-Medicare, 183 patients with MPC were identified, and 63 (34%) underwent RC. In the institutional cohort, patients with MPC had significantly higher incidence of cN+ (17% vs. 8%), pN+ stage (30% vs. 17%), carcinoma-in-situ (43% vs. 25%), and lymphovascular invasion (30% vs. 16%) at RC versus those with CUC (all P < .05). Pathologic complete response (ypT0N0) to NAC was 33% for MPC and 35% for CUC (P = .899). Median OS was lower for institutional MPC versus CUC in univariate analysis (43.6 vs. 105.3 months, P = .006); however, MPC was not independently associated with OS in the multivariate model. Median OS was 25 months in the SEER MPC cohort for patients undergoing RC, while NAC was not associated with improved OS in that group.

CONCLUSION

Pathologic response to NAC was not significantly different between MPC and CUC, while MPC histology was not an independent predictor of OS. Further studies are needed to better understand biological mechanisms behind its aggressive features as well as the role of NAC in this histology variant.

Current Management of Localized Muscle-Invasive Bladder Cancer: A Consensus Guideline from the Genitourinary Medical Oncologists of Canada

BACKGROUND: Despite recent advances in the management of muscle-invasive bladder cancer (MIBC), treatment outcomes remain suboptimal, and variability exists across current practice patterns. OBJECTIVE: To promote standardization of care for MIBC in Canada by developing a consensus guidelines using a multidisciplinary, evidence-based, patient-centered approach who specialize in bladder cancer. METHODS: A comprehensive literature search of PubMed, Medline, and Embase was performed; and most recent guidelines from national and international organizations were reviewed. Recommendations were made based on best available evidence, and strength of recommendations were graded based on quality of the evidence. RESULTS: Overall, 17 recommendations were made covering a broad range of topics including pathology review, staging investigations, systemic therapy, local definitive therapy and surveillance. Of these, 10 (59% ) were level 1 or 2, 7 (41% ) were level 3 or 4 recommendations. There were 2 recommendations which did not reach full consensus, and were based on majority opinion. This guideline also provides guidance for the management of cisplatin-ineligible patients, variant histologies, and bladder-sparing trimodality therapy. Potential biomarkers, ongoing clinical trials, and future directions are highlighted. CONCLUSIONS: This guideline embodies the collaborative expertise from all disciplines involved, and provides guidance to further optimize and standardize the management of MIBC.

Micropapillary Versus Urothelial Carcinoma of the Urinary Bladder: Stage at Presentation and Efficacy of Chemotherapy Across All Stages-A SEER-based Study

BACKGROUND

Stage-specific guideline recommendations are lacking for chemotherapy in micropapillary carcinoma of the urinary bladder (MCUB).

OBJECTIVE

To test the efficacy of stage-specific chemotherapy for MCUB.

DESIGN, SETTING, AND PARTICIPANTS

Within the Surveillance, Epidemiology and End Results (SEER) registry (2001-2016), we identified patients with MCUB and pure urothelial carcinoma of the urinary bladder (UCUB) of all stages.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Kaplan-Meier survival analyses and multivariate Cox regression models were used to determine cancer-specific mortality (CSM) in addition to power analyses.

RESULTS AND LIMITATIONS

Of 210 491 patients of all stages, 518 (0.2%) harboured MCUB versus 209 973 (99.8%) UCUB. Stage at presentation was invariably higher in MCUB than in UCUB patients. Of the MCUB patients, 223 (43.1%) received chemotherapy versus 42 921 (20.4%) of the UCUB patients. In MCUB patients, chemotherapy improved CSM-free survival significantly in metastatic stage (hazard ratio [HR] 0.36, p = 0.04). Longer median CSM-free survival was also associated with chemotherapy use in addition to radical cystectomy (RC) versus RC alone in non-organ-confined MCUB (HR 0.69, p = 0.2). Additional power analyses revealed an underpowered comparison. Finally, no CSM difference was recorded in organ-confined MCUB according to the use of chemotherapy in addition to RC versus RC alone (HR 0.98, p = 1).

CONCLUSIONS

Stage at presentation was invariably higher in MCUB than in UCUB patients. Very important CSM reduction was associated with chemotherapy use in metastatic MCUB. A promising protective effect of perioperative chemotherapy might also be applicable to non-organ-confined MCUB, but without sufficient statistical power. Conversely, no association was recorded in organ-confined MCUB.

PATIENT SUMMARY

Patients with micropapillary carcinoma of the urinary bladder (MCUB) present in higher tumour stages than those with urothelial carcinoma of the urinary bladder. Chemotherapy for MCUB is effective in metastatic stages, but of no beneficial effect in organ-confined stage. In not-yet-metastatic but already non-organ-confined stages, we did not have enough observations to show a statistically significant protective effect of chemotherapy.

Prognostic values of the clinicopathological characteristics and survival outcomes in micropapillary urothelial carcinoma of the bladder: A SEER database analysis

Purpose

To study prognostic values of the clinicopathological characteristics and survival outcomes in micropapillary urothelial carcinoma (MPUC) of the urinary bladder.

Method

We used the national Surveillance, Epidemiology, and End Results database (2004‐2016) to compare MPUC with transitional cell carcinoma (TCC) and to investigate prognostic values of clinicopathological characteristics, as well as survival outcomes, in MPUC of the urinary bladder. A multivariable Cox proportional hazard model, subgroup analyses, and propensity score matching were used.

Results

In all, 519 patients with MPUC and 154 453 patients with TCC were enrolled. Compared with TCC, patients with MPUC had a higher rate of muscle invasive disease (P < .001), lymph node metastasis (P < .001), and distal metastasis (P < .001), as well as higher tumor grade (P < .001). According to the survival analyses, the MPUC group also had lower survival probability in both cancer‐specific mortality (CSM) (P < .0001) and overall mortality (OM) analyses (P < .0001). Cox proportional hazard regression showed that the MPUC group had a higher risk of OM (hazard ratios [HR] = 1.39, 95% confidence intervals [CI] = 1.22‐1.57, P < .0001), although the CSM (HR = 1.18, 95% CI = 1.00‐1.40, P = .0505) in that group was fair. In the subgroup analysis, only MPUC patients without distal metastasis faced a higher risk of CSM (HR = 1.33, 95% CI = 1.101.61, P < .0001).

Conclusions

Micropapillary urothelial carcinoma prognosis is poorer than that of TCC. Micropapillary urothelial carcinoma is an independent prognostic factor for OM in patients with urinary bladder cancer.

Micropapillary urothelial carcinoma of urinary bladder displays immunophenotypic features of luminal and p53-like subtypes and is not a variant of adenocarcinoma

OBJECTIVES

Micropapillary urothelial carcinoma of the urinary bladder (MPUC) is a rare variant of urothelial carcinoma which has aggressive clinical characteristics. The objective is to investigate the molecular subtypes of MPUC and the impact to the clinical outcome and determine whether MPUC represents a variant of adenocarcinoma.

MATERIALS AND METHODS

We evaluated surrogate immunohistochemical markers of luminal, basal, and p53-like subtypes and correlated with prognosis and the expression of markers related to bladder adenocarcinoma and glandular differentiation in 56 cases of MPUC (10 cases of transurethral resection and 46 cases of radical cystectomy). Biomarker expression in co-existing conventional urothelial carcinoma was also analyzed. Cox regression analysis was performed to study the impact of molecular subtype on the clinical outcome.

RESULTS

Thirty-four cases (61%) met criteria for the luminal subtype. Twenty-two cases (39%) displayed a p53-like subtype. In contrast, 40/56 (71%) cases of coexisting conventional urothelial carcinoma were classified as luminal subtype and 16/56 (29%) cases were designated as p53-like subtype. There was no significant survival difference between luminal subtype and p53-like subtype. CDX2, villin, and cadherin 17 were negative in all cases. MUC1 was strongly and diffusely expressed in the stroma-facing surface of MPUC tumor cells in all the cases.

CONCLUSIONS

Our findings suggest that MPUC possesses characteristics of luminal and p53-like subtypes, and does not harbor phenotypic features of the basal subtype. There is no significant difference in the prognosis between luminal and p53-like subtype MPUC. MPUC is not a variant of adenocarcinoma and does not represent a form of glandular differentiation, in contrast to other organ sites.

Molecular and histopathology directed therapy for advanced bladder cancer

Bladder cancer is a heterogeneous group of tumours with at least 40 histological subgroups. Patients with localized disease can be cured with surgical resection or radiotherapy, but such curative options are limited in the setting of recurrent disease or distant spread, in which case systemic therapy is used to control disease and palliate symptoms. Cytotoxic chemotherapy has been the mainstay of treatment for advanced bladder cancer, but high-quality evidence is lacking to inform the management of rare subgroups that are often excluded from studies. Advances in molecular pathology, the development of targeted therapies and the resurgence of immunotherapy have led to the reclassification of bladder cancer subgroups and rigorous efforts to define predictive biomarkers for cancer therapies. In this Review, we present the current evidence for the management of conventional, variant and divergent urothelial cancer subtypes, as well as non-urothelial bladder cancers, and discuss how the integration of genomic, transcriptomic and proteomic characterization of bladder cancer could guide future therapies.

Computed tomography-based texture analysis of bladder cancer: differentiating urothelial carcinoma from micropapillary carcinoma

PURPOSE

The purpose of the study is to determine the feasibility of using computed tomography-based texture analysis (CTTA) in differentiating between urothelial carcinomas (UC) of the bladder from micropapillary carcinomas (MPC) of the bladder.

METHODS

Regions of interests (ROIs) of computerized tomography (CT) images of 33 MPCs and 33 UCs were manually segmented and saved. Custom MATLAB code was used to extract voxel information corresponding to the ROI. The segmented tumors were input to a pre-existing radiomics platform with a CTTA panel. A total of 58 texture metrics were extracted using four different texture extraction techniques and statistically analyzed using a Wilcoxon rank-sum test to determine the differences between UCs and MPCs.

RESULTS

Of the 58 texture metrics extracted using the gray level co-occurrence matrix (GLCM) and gray level difference matrix (GLDM), 28 texture metrics were statistically significant (p < 0.05) for differences in tumor textures and 27 texture metrics were statistically significant (p < 0.05) for peritumoral fat textures. The remaining nine metrics extracted using histogram and fast Fourier transform analyses did not show significant differences between the textures of the tumors and their peritumoral fat.

CONCLUSIONS

CTTA shows that MPC have a more heterogeneous texture compared to UC. As visual discrimination of MPC from UC from clinical CT scans are difficult, results from this study suggest that tumor heterogeneity extracted using GLCM and GLDM may be a good imaging aid in segregating MPC from UC. This tool can aid clinicians in further sub-classifying bladder cancers on routine imaging, a process which has potential to alter treatment and patient care.

Cell Polarity Reversal Distinguishes True Micropapillary Growth From Retraction Artifact in Invasive Urothelial Carcinoma

Focal micropapillary features in invasive urothelial carcinoma is sometimes difficult to distinguish from retraction artifact morphologically. Cell polarity reversal has been demonstrated in micropapillary tumors by epithelial membrane antigen (EMA) immunostaining. We have previously described the use of E-cadherin as a cell polarity marker in ovarian micropapillary serous borderline tumors. The aim of this study was to evaluate the utility of immunohistochemistry for EMA and E-cadherin in differentiating micropapillary urothelial carcinoma from retraction artifact. We identified 29 invasive urothelial carcinomas with micropapillary features and 30 invasive urothelial carcinomas without reported micropapillary features but with areas of retraction artifact. Cell polarity reversal was considered present if E-cadherin showed membranous apical cup-like staining or if EMA demonstrated a well-defined basal staining towards the stroma. Twenty-seven of 29 cases (93%) of urothelial carcinoma with micropapillary features demonstrated EMA or E-cadherin staining patterns consistent with cell polarity reversal. Staining consistent with micropapillary architecture was identified with both markers in 20 of these 27 cases (74%). Six cases showed reversal of polarity by E-cadherin alone, whereas 1 case showed polarity reversal by EMA alone. Retraction artifacts showed circumferential staining by E-cadherin and lacked well-defined basal staining by EMA. Three cases originally classified as with retraction artifact showed reversal of cell polarity by both EMA and E-cadherin and were reclassified as micropapillary. Our data show that pathologists can reliably make this distinction in most cases. However, in some cases with ambiguous features, EMA and E-cadherin immunostaining may aid in resolving this diagnostic dilemma.

Advances in risk stratification of bladder cancer to guide personalized medicine

Bladder cancer is a heterogeneous disease that poses unique challenges to the treating clinician. It can be limited to a relatively indolent papillary tumor with low potential for progression beyond this stage to muscle-invasive disease prone to distant metastasis. The former is best treated as conservatively as possible, whereas the latter requires aggressive surgical intervention with adjuvant therapies in order to provide the best clinical outcomes. Risk stratification traditionally uses clinicopathologic features of the disease to provide prognostic information that assists in choosing the best therapy for each individual patient. For bladder cancer, this informs decisions regarding the type of intravesical therapy that is most appropriate for non-muscle-invasive disease or whether or not to administer neoadjuvant chemotherapy prior to radical cystectomy. More recently, tumor genetic sequencing data have been married to clinical outcomes data to add further sophistication and personalization. In the next generation of risk classification, we are likely to see the inclusion of molecular subtyping with specific treatment considerations based on a tumor’s mutational profile.