Outcomes following radical cystectomy for micropapillary bladder cancer versus pure urothelial carcinoma: a matched cohort analysis

Advances, recognition, and interpretation of molecular heterogeneity among conventional and subtype histology of urothelial carcinoma (UC): a survey among urologic pathologists and comprehensive review of the literature

AIMS

Urothelial carcinoma (UC) demonstrates significant molecular and histologic heterogeneity. The WHO 2022 classification has hinted at adding molecular signatures to the morphologic diagnosis. As morphology and associated molecular repertoire may potentially translate to choices of and response to therapy and relapse rate, broader acceptability of recognizing these key features among uropathologists is needed. This prompted an international survey to ascertain the practice patterns in classical/subtype UC among uropathologists across the globe.

METHODS AND RESULTS

A survey instrument was shared among 98 uropathologists using SurveyMonkey software. Anonymized respondent data were analysed. The response rate was 85%. A majority were in concordance with the profiles of luminal (93%) and basal (82%) types. Opinion on the FGFR3 testing platform was variable. While 95% concurred that TERT promoter mutation is the key driver in UC, 72% had the opinion that APOBEC mutagenesis is the main signature in muscle invasive bladder cancer (MIBC). Uropathologists have divergent opinions on MIBC and ERCC2 mutations. Among the participants, 94% would quantify aggressive micropapillary and sarcomatoid histology, while 88% would reevaluate another transurethral resection of the bladder tumour specimen in nonmuscle invasive tumour with micropapillary, small cell, or sarcomatoid histology. A leading number agreed to specific molecular signatures of micropapillary (93%), plasmacytoid (97%), and small cell (86%) subtypes. Ninety-six percent of participants agreed that a small-cell component portends a more aggressive course and should be treated with neoadjuvant chemotherapy and 63% would perform HER2/neu testing only on oncologist's request in advanced tumours. Ninety percent agreed that microsatellite instability testing, although not a standard protocol, should be considered in young patients with upper tract UC. Eighty-six percent agreed that UC with high tumour mutational burden would be a better candidate for immunotherapy.

CONCLUSION

In the era of precision medicine, enhanced understanding of molecular heterogeneity of UC will contribute to better therapeutic options, novel biomarker discovery, innovative management protocols, and outcomes. Our survey provides a broad perspective of pathologists' perceptions and experience regarding incorporation of histomolecular approaches to "personalize" therapy. Due to variable clinical adoption, there is a need for additional data using uniform study criteria. This will drive generation of best practice guidelines in this area for widespread and consistent clinical utility.

Impact of Neoadjuvant Chemotherapy on Pathologic Downstaging in Patients With Variant Histology Undergoing Radical Cystectomy

INTRODUCTION

Variant histology (VH) bladder cancer is often associated with poor outcomes and the role of neoadjuvant chemotherapy (NAC) remains incompletely defined. Our objective was to determine comparative pathologic downstaging at radical cystectomy (RC) following NAC for patients with and without VH.

PATIENTS AND METHODS

Patients who underwent RC at 2 tertiary referral centers (1996-2018) were included. Patients with VH (sarcomatoid, nested, micropapillary, plasmacytoid) were matched 1:2 to patients with pure urothelial carcinoma by age, sex, clinical T (cT)stage, clinical N (cN)stage, cystectomy year and receipt of NAC. The primary outcome was pathologic downstaging (pT-stage < cT-stage). The differential impact of NAC on pathologic downstaging between VH and non-VH was assessed using multivariable logistic regression with interaction analysis.

RESULTS

225 VH and 437 non-VH patients were included. One hundred twenty-eight of six hundred sixty-two (19.3%) patients experienced downstaging, including 54/121 (44.6%) patients who received NAC and 74/542 (13.2%) patients who did not (P < .01). Rates of downstaging after NAC for subgroups were: 45/78 (57.7%) urothelial, 3/8 (37.5%) sarcomatoid, 2/12 (16.7%) nested, 3/14 (21.4%) micropapillary, and 1/8 (12.5%) plasmacytoid. Collectively, 9/42 (21.4%) of VH patients who received NAC were downstaged. On multivariable analyses, NAC was associated with increased likelihood of downstaging in the overall cohort (OR 5.25, 95% CI, 3.29-8.36, P < .0001) and this effect was not modified by VH versus non-VH histology (P = .13 for interaction). VH patients had worse survival outcomes compared to non-VH (P < 0.01 for all).

CONCLUSION

When comparing patients with VH to matched pure urothelial carcinoma controls, VH did not have an adverse effect on downstaging following NAC. VH patients should not be excluded from NAC if otherwise eligible.

Urinary tract cytology showing variant morphology and divergent differentiation

Urothelial carcinoma represents a diverse group of tumours with distinct histologic subtypes, each exhibiting unique cytomorphologic features, architectural growth patterns, and/or well-developed aberrant differentiation. In fact, there are more than 13 subtypes of urothelial carcinoma recognized in the 2022 WHO classification of tumours in the urinary tract. The identification of these subtypes is crucial for an accurate diagnosis of urothelial carcinoma, and many have important clinical implications. Variant/divergent features may coexist with conventional high-grade urothelial carcinoma (HGUC) or present with 100% variant morphology. In urinary tract cytology (UTC), urothelial carcinoma can display divergent differentiation, such as squamous, glandular, or small cell carcinoma differentiation. The use of cell block preparations and immunohistochemistry with available residual urine can enhance diagnostic accuracy. On the other hand, identifying urothelial carcinoma variants, including nested, micropapillary, and plasmacytoid subtypes, poses significant challenges in UTC. Many cases of these variants are only detected retrospectively after variant histology has been established from resection specimens. Moreover, some variants exhibit features inconsistent with the diagnostic criteria for HGUC according to the Paris System for Reporting Urinary Tract Cytology. Nevertheless, the rarity of pure variant morphology and the occurrence of some false negatives for these variant cases are essential to maintain the specificity of UTC overall. This review covers the histology, cytomorphology, and important clinical aspects observed in urothelial carcinoma exhibiting divergent differentiation and various urothelial carcinoma variants detected in UTC.

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.

Clinicopathologic Analysis of Micropapillary Urothelial Carcinoma of the Upper Urinary Tract: Implications for HER2-Targeted Therapy

Introduction/Background To determine the clinical significance of micropapillary urothelial carcinoma (MPUC) of the upper urinary tract (UTUC) and a potential therapeutic strategy. Patients and Methods A retrospective cohort study was conducted to examine the incidence of micropapillary UTUC from 2010 to 2018 and its clinicopathological characteristics. Clinical outcomes and cancer-specific survival (CSS) were compared between MPUC and conventional UTUC matched by stage within a 6-month variation of receiving surgery. Results A total of 24 MPUC cases were identified out of 901 cases (2.7%) of urothelial carcinoma (UC) of the renal pelvis and ureter. MPUC was significantly smaller (<3 cm) and associated with nodal metastasis compared with conventional UTUC (P = .017 & 0.021, respectively); however, no significant difference was observed for lymphovascular invasion, distant metastasis, or CSS (P > 0.50, respectively) compared with match controls. Six MPUC patients (25%) developed metastasis to the liver, lymph nodes, and lung during follow-up. Patients with HER2-positive MPUC (3 of 4) had a significantly higher risk of metastasis compared with HER2-negative MPUC (3 of 20; P = 0.035). Conclusions MPUC is an aggressive variant of UTUC and usually presents as a small locally advanced disease. HER2 immunohistochemistry may identify the subset of patients with micropapillary UTUC that are candidates for targeted therapy.

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: 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.

Overview of histologic variants of urothelial carcinoma: current trends and narrative review on treatment outcomes

Background and Objective

The histologic variants of urothelial carcinoma (UC) are tumors arising from within the urothelium in which some component of the tumor morphology is other than urothelial. They are underdiagnosed, aggressive and have varying pathologic response rates to systemic chemotherapy. There are no consensus guidelines on the use of systemic chemotherapy in variant histology (VH) of UC. We performed a contemporary review on pathologic response rates to neoadjuvant systemic therapy and survival outcomes following radical cystectomy in order to provide a rationale for clinical practice recommendations on the management of UC with VH.

Methods

A PubMed literature search was conducted for all English articles from inception reporting either pathological response rates to neoadjuvant treatment or survival outcomes after radical cystectomy in non-metastatic VH of UC.

Key Content and Findings

Neoadjuvant chemotherapy (NAC) prior to radical cystectomy was shown to be a beneficial treatment strategy in UC with VH. The micropapillary, plasmacytoid, nested and sarcomatoid histologic variants were associated with worse survival outcomes compared to conventional UC and UC with squamous or glandular differentiation despite initial downstaging with chemotherapy. There is evidence of improved survival in patients with sarcomatoid differentiation receiving NAC compared to RC alone. The major prognostic factors that affect survival outcomes in VH of UC include histologic variant subtype, patient age, presence of lymphovascular invasion, hydronephrosis, nodal metastasis and advanced T stage at diagnosis. Recent studies demonstrate that VH of UC are heterogenous tumors and responsiveness to NAC may be a function of the molecular subtypes present.

Conclusions

Based on these findings, NAC to achieve pathologic downstaging prior to radical cystectomy is recommended for MIBC with VH. Biomarkers identified by molecular profiling with immunohistochemistry will need to be validated as predictors of response to NAC in future trials.

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.

Evaluation of the Extent of Variant Histology in Urothelial Carcinoma as a Predictive Marker of Clinical Outcomes After Radical Cystectomy

BACKGROUND/AIM

This study investigated the impact of the extent of variant histology (VH) on the prognosis of patients with bladder cancer (BC).

PATIENTS AND METHODS

We retrospectively evaluated consecutive patients with muscle-invasive BC who were treated with radical cystectomy (RC) at our institution between 2005 and 2018. Recurrence-free survival (RFS) and overall survival (OS) rates were evaluated using Kaplan-Meier analysis and Cox regression.

RESULTS

We identified 103 and 47 patients with pure urothelial carcinoma (UC) and a VH in UC, respectively. At the cutoff of 80%, univariate analysis identified significant differences in RFS (p=0.046) and OS (p=0.038) between patients with ≥80% VH (n=21) and those with <80% VH (n=26). Multivariate analysis revealed that the presence of ≥80% VH was significantly associated with RFS and OS.

CONCLUSION

The presence of ≥80% VH in UC could be an independent predictor of recurrence and mortality after RC.

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

The Genitourinary Pathology Society (GUPS) undertook a critical review of the recent advances in bladder cancer focusing on important topics of high interest for the practicing surgical pathologist and urologist. This review represents the second of 2 manuscripts ensuing from this effort. Herein, we address the effective reporting of bladder cancer, focusing particularly on newly published data since the last 2016 World Health Organization (WHO) classification. In addition, this review focuses on the importance of reporting bladder cancer with divergent differentiation and variant (subtypes of urothelial carcinoma) histologies and the potential impact on patient care. We provide new recommendations for reporting pT1 staging in diagnostic pathology. Furthermore, we explore molecular evolution and classification, emphasizing aspects that impact the understanding of important concepts relevant to reporting and management of patients.

ACR Appropriateness Criteria® Post-Treatment Surveillance of Bladder Cancer: 2021 Update

Urothelial cancer is the second most common cancer, and cause of cancer death, related to the genitourinary tract. The goals of surveillance imaging after the treatment of urothelial cancer of the urinary bladder are to detect new or previously undetected urothelial tumors, to identify metastatic disease, and to evaluate for complications of therapy. For surveillance, patients can be stratified into one of three groups: 1) nonmuscle invasive bladder cancer with no symptoms or additional risk factors; 2) nonmuscle invasive bladder cancer with symptoms or additional risk factors; and 3) muscle invasive bladder cancer. This document is a review of the current literature for urothelial cancer and resulting recommendations for surveillance imaging. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

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.

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.

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.

ACR Appropriateness Criteria® Post-Treatment Surveillance of Bladder Cancer

Urothelial cancer is the second most common cancer, and cause of cancer death, related to the genitourinary tract. The goals of surveillance imaging after the treatment of urothelial cancer of the urinary bladder are to detect new or previously undetected urothelial tumors, to identify metastatic disease, and to evaluate for complications of therapy. For surveillance, patients can be stratified into one of three groups: (1) nonmuscle invasive bladder cancer with no symptoms or additional risk factors; (2) nonmuscle invasive bladder cancer with symptoms or additional risk factors; and (3) muscle invasive bladder cancer. This article is a review of the current literature for urothelial cancer and resulting recommendations for surveillance imaging. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Histologic Variants of Urothelial Carcinoma: Morphology, Molecular Features and Clinical Implications

Bladder cancer is a heterogeneous disease including conventional urothelial carcinoma (UC) and its histologic variants, and non-urothelial carcinoma, including squamous and glandular neoplasms. Urothelial carcinoma accounts for the majority of bladder cancer cases, but morphologic variants are common and include nested, microcystic, micropapillary, lymphoepithelioma-like, plasmacytoid, sarcomatoid, giant cell, undifferentiated, clear cell and lipoid. Certain variants of UC tend to be associated with a poor prognosis and have diagnostic and potential treatment implications that make the identification of variant histology crucial to clinical decision making. While there is still uncertainty regarding the prognostic implications of many of these variants, identifying and reporting variant histology is important to develop our understanding of their biology. Unique molecular features accompany many of these morphologic variants and to better understand these tumors, we review the molecular and clinical implications of histologic variants of bladder cancer. Major efforts are underway to include variant histology and divergent differentiation of UC in clinical trials to develop evidence based approaches to treatment. The purpose of this article is to review the current literature on variant histology of urothelial cancer and to highlight molecular findings and the clinical relevance of these tumors.

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.

Updates on the Genomics of Bladder Cancer and Novel Molecular Taxonomy

Urothelial carcinoma (UC) is the most common malignant neoplasm of the bladder that encompasses a wide spectrum of histopathologic features and various molecular alterations and subtypes, responsible for its significant morphologic and genomic heterogeneity. Morphologically, in addition to classic UC (not otherwise specified), many well documented variant histologies are a common finding in invasive UC, and include squamous, glandular, micropapillary, sarcomatoid, small cell/neuroendocrine, clear cell, lymphoepithelioma-like, and plasmacytoid types, among others. This review provides an update on the recent advances in the molecular characterization and novel molecular taxonomy of UC and variant histologies.

Trends in the use of neoadjuvant chemotherapy for bladder cancer with nonurothelial variant histology: An analysis of the National Cancer Database

Introduction

The aim of this study is to evaluate the trends in the use of neoadjuvant chemotherapy (NAC) over time (2006-2014) for patients diagnosed with muscle-invasive bladder cancer (MIBC) with nonurothelial variant histology (NUVH) in the National Cancer Database.

Materials and Methods

We queried the NCDB for patients with muscle-invasive (i.e. cT2-4N0-3M0/X) urothelial carcinoma (UC) of the bladder. We examined demographic, clinical, and pathologic features associated with NAC, also substratifying into pure UC and NUVH. Tests of association were performed using Chi-square/Fisher's exact test for categorical variables and t-tests, ANOVA, or Kruskal-Wallis test for continuous variables. Outcomes were examined with Cox proportional hazards and 90-day mortality with the Kaplan-Meier method.

Results

Totally 22,320 patients met our inclusion criteria, of whom 22.6% received NAC. The proportion of NAC increased significantly over time in the neuroendocrine and urothelial cell categories with 57.1% and 34.1% of patients in 2014 receiving NAC vs. 44% and 10.6% in 2006. No other variant histology showed a significant increase across the time sampled. Patients receiving NAC were more likely to have downstaging to pT0 (13.4% vs. 2.7%), negative surgical margin (89.1% vs. 86%), and pN0 (63.2% vs. 60.5%) and were less likely to have 30-day (1.4% vs. 3%) or 90-day (5% vs. 8.3%) mortality. Rates of downstaging to pT0 after NAC were similar among histologies.

Conclusion

Neoadjuvant chemotherapy utilization continues to slowly increase in patients with MIBC. Patients with variant histology lag behind in terms of receiving NAC but appear to derive as much benefit as patients with pure urothelial cell bladder cancer.

Prognostic and therapeutic role of HER2 expression in micropapillary carcinoma of the bladder

Micropapillary carcinoma of the bladder (MPBC) is a variant type of infiltrating urothelial carcinoma, which portends a poor biological behavior in terms of disease stage at first diagnosis and clinical outcome; its peculiar morphology raises issues concerning the ability of tumor detection by imaging techniques and proper biopsy procedure, and the appropriate treatment for non-muscle infiltrating and muscle-infiltrating MPBC remains a matter of debate. On the basis of its established prognostic and therapeutic role in breast and gastro-esophageal cancer in the first instance, the human epidermal growth factor receptor-2 (HER2) has been investigated in selected case series of MPBC over the last 10 years. The aim of the present review was to summarize the existing evidence on HER2 status in MPBC, and to discuss its present and future utility in risk assessment and treatment choice of this uncommon, yet aggressive, disease.

Intratumoral heterogeneity of ERBB2 amplification and HER2 expression in micropapillary urothelial carcinoma

Micropapillary urothelial carcinoma (MPUC) is a rare but an aggressive variant of urothelial carcinoma. MPUC has been shown to commonly exhibit ERBB2 amplification and HER2 protein overexpression, but the frequency and distribution of these findings within micropapillary (MP) and not otherwise specified (NOS) components of tumors with mixed histology have not been addressed. Therefore, we evaluated ERBB2 amplification and HER2 expression in 43 MPUC cases by fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC). Of the 35 tumors containing both MP and NOS components, ERBB2 amplification was present in both the MP and NOS components of 12 tumors (34.3%), in only the MP component of 11 tumors (31.4%), and exclusively in the NOS component of 4 tumors (11.4%). HER2 protein overexpression was significantly more commonly present in the MP component compared to the NOS component within the same tumor (68.6% versus 34.3%, P = .012). Overall, there was a moderately positive correlation between HER2 protein expression and ERBB2 amplification in both MP (ρ = 0.59, P < .001) and NOS (ρ = 0.70, P < .001) components. All MP/NOS areas with IHC score 3+ and none of MP/NOS areas with IHC score 0 were associated with ERBB2 amplification. We conclude that ERBB2 amplification and HER2 overexpression are preferentially but not exclusively identified in the MP component compared to the NOS component within the same tumor. Our findings identify the presence of intratumoral heterogeneity of ERBB2 amplification and HER2 expression in MPUC and provide grounds for further investigation into the mechanisms underlying the development of MPUC.

Clinical risk stratification in patients with surgically resectable micropapillary bladder cancer

OBJECTIVE

To analyse survival in patients with clinically localised, surgically resectable micropapillary bladder cancer (MPBC) undergoing radical cystectomy (RC) with and without neoadjuvant chemotherapy (NAC) and develop risk strata based on outcome data.

PATIENTS AND METHODS

A review of our database identified 103 patients with surgically resectable (≤cT4acN0 cM0) MPBC who underwent RC. Survival estimates were calculated using Kaplan-Meier method and compared using log-rank tests. Classification and regression tree (CART) analysis was performed to identify risk groups for survival.

RESULTS

For the entire cohort, estimated 5-year overall survival and disease-specific survival (DSS) rates were 52% and 58%, respectively. CART analysis identified three risk subgroups: low-risk: cT1, no hydronephrosis; high-risk: ≥cT2, no hydronephrosis; and highest-risk: cTany with tumour-associated hydronephrosis. The 5-year DSS for the low-, high-, and highest-risk groups were 92%, 51%, and 17%, respectively (P < 0.001). Patients down-staged at RC <pT1 regardless of the use of NAC had the best survival (5-year DSS of 96% vs 45% for those not down-staged; P < 0.001), while those who were not down-staged despite NAC had 5-year DSS of only 17%.

CONCLUSION

In patients with surgically resectable MPBC, NAC appears to confer benefit to patients with muscle-invasive disease without hydronephrosis, while patients with cT1 disease can proceed to upfront RC. Patients with hydronephrosis do not appear to respond well to NAC and have poor prognosis regardless of treatment paradigm. However, further external validation studies are needed to support the proposed risk stratification before treatment recommendations can be made.

The Response of Variant Histology Bladder Cancer to Intravesical Immunotherapy Compared to Conventional Cancer

Background

High-grade urothelial carcinomas (UCs) often show foci of variant differentiation. There is limited information in the literature about the response of these variant urothelial tumors to immunotherapy with bacillus Calmette–Guerin (BCG). We compared the response, to treatment with BCG, of UC containing glandular, squamous, nested, and micropapillary types of differentiation to response of conventional non-muscle invasive high-grade UC.

Methods

A total of 100 patients were diagnosed with variant histology urothelial cancer between June 1995 and December 2013. Forty-one patients with Ta or T1, confirmed by second look biopsies, received immunotherapy with BCG. Fourteen patients in this group were diagnosed with micropapillary differentiation, 13 patients with squamous differentiation, 9 patients with glandular differentiation, and 7 patients with nested variants. The control group included 140 patients with conventional high-grade UC. Both groups have been treated and followed similarly.

Findings

Patients with variant tumors had similar clinical features to patients with conventional disease, including age, male to female ratio, stage, the presence of Tis, and median follow-up. Patients with variant tumors had a significantly worse prognosis compared to patients with conventional high-grade UC, including 5-year recurrence-free survival (63.5 Vs. 71.5%, p = 0.05), 5-year progression (≥T2)-free survival (60 Vs. 82.5%, p = 0.002), 5-year disease-specific survival (73 Vs. 92.5%, p = 0.0004), and overall survival (66 Vs. 89.5%, 0.05).

Interpretation

A patient with variant bladder cancer treated with intravesical immunotherapy has a 27% chance of dying from this disease within 5 years compared to 7.5% chance for a patient with conventional high-grade UC.

A case report of urothelial carcinoma with combined micropapillary and plasmacytoid morphology in the urinary bladder

A case of combined micropapillary and plasmacytoid urothelial carcinoma (UC) of the urinary bladder is presented for a 74-year-old male who was admitted to the hospital with gross hematuria and multifocal papillary bladder tumors. Abdominal computed tomography showed a large enhancing mass on the left lateral and anterior wall of the urinary bladder, which was highly suspicious for extravesicular extension and focal extension of the anterior lesion to the pubic bone. In voided urine, cancer cells were scattered as micropapillae or nests as well as single cells on the low power view. On a higher power view, micropapillae or nests were composed of pleomorphic, high grade tumor cells with an inverted nuclear arrangement and with acinar structures occasionally identified. Single cells were discohesive and large with a thick cytoplasm and eccentrically located nuclei. Histologically, the tumor from the resected bladder showed diffusely infiltrating micropapillae or nests with a surrounding halo and dense singly-scattered plasmacytoid cells. Immunohistochemically, the cancer cells were positive for cytokeratin-7 and cytokeratin-20 but negative for S-100, leukocyte common antigen, and vimentin. At the time of radical cystectomy, severe adhesions and peritoneal metastases were found and the surgery was discontinued. The patient received systemic chemotherapy, but died of bladder cancer 14 months after surgery.

The Prognostic Impact of Histopathological Variants in Patients with Advanced Urothelial Carcinoma

Purpose

This study investigated the prognostic role of histopathological variants in patients with advanced urothelial carcinoma (UC) who were treated with systemic chemotherapy.

Materials and Methods

We conducted a retrospective analysis of patients with unresectable and/or metastatic UC who underwent systemic chemotherapy between January 1997 and December 2013 in Kaohsiung Chang Gung Memorial Hospital. Histopathological types were categorized as pure UC (PUC) and variants of UC (VUC). The overall survival (OS) and progression-free survival (PFS) were calculated using Kaplan–Meier analyses and Cox proportional regression models.

Results

A total of 206 patients were enrolled; 53 of the patients (25.7%) had histopathological variants. The most common variant was squamous differentiation (68%). Compared with patients with PUC, patients with VUC significantly exhibited upper urinary tract origin (75% vs 52%, P = .008), chronic renal insufficiency (40% vs 23%, P = .03), and carboplatin-based chemotherapy (28% vs 10%, P = .003). According to univariate analysis, the median OS for PUC patients was significantly higher than that for VUC patients (15.9 vs 11.3 months, P = .007). The median PFS for patients who received first-line chemotherapy was 6.1 and 3.8 months for PUC patients and VUC patients, respectively (P = .004). Multivariate analysis revealed that VUC (hazard ratio [HR] 1.67, 95% confidence interval [CI] 1.16–2.40, P = .006), an age ≤ 60 years (HR 0.70, 95% CI 0.49–0.99, P = .045) and presence of visceral metastasis (HR 1.54, 95% CI 1.11–2.13, P = .009) were independent factors facilitating OS prediction.

Conclusions

The presence of histopathological variants indicates poor survival outcomes in patients with metastatic UC. Accordingly, VUC should be integrated into and considered an independent factor in a predictive model of survival.

Is Immediate Radical Cystectomy Necessary for All Patients with Non-Muscle-Invasive Micropapillary Bladder Cancer?

INTRODUCTION

We aim to review the outcomes of micropapillary urothelial carcinoma (MPUC) of the bladder from a single institution. The hypothesis is that non-muscle-invasive (NMI) MPUC may have a heterogeneous prognosis, and detailed pathological analysis may identify patients that could be managed without immediate cystectomy.

PATIENTS AND METHODS

This is a retrospective analysis of patients presenting with MPUC in a primary transurethral resection specimen (n = 40). The pattern of micropapillary (MP) differentiation [surface/non-invasive (sMP) or invasive (iMP)], extent of MP differentiation and lymphovascular invasion (LVI) were correlated with overall survival (OS), recurrence-free survival and upstaging at re-resection.

RESULTS

Sixteen of 40 patients died after a median follow-up of 37 months. Tumour stage was strongly predictive of OS (p < 0.0001). LVI was associated with increased mortality (hazard ratio 12.4, 95% CI: 3.5-44.5, p = 0.0001), higher pathological stage (p = 0.001), lymph node involvement (p = 0.001) and iMP differentiation (p = 0.006). In NMI patients not undergoing cystectomy (n = 17), NMI-sMP compared with NMI-iMP differentiation was associated with an improved OS when compared with iMP (63 vs. 47 months, p = 0.05).

CONCLUSIONS

MPUC is an aggressive variant of urothelial carcinoma (UC). Similar to conventional UC, LVI associated with MPUC is an adverse prognostic indicator. iMP is a morphological marker for LVI. Histopathological reports should distinguish between sMP and iMP differentiation.

Clinical outcomes of cT1 micropapillary bladder cancer

PURPOSE

While many urologists recommend radical cystectomy for micropapillary bladder cancer invading the lamina propria (cT1), contradictory small reports exist on the efficacy of conservative management with intravesical bacillus Calmette-Guérin for this disease. We report our updated experience in what to our knowledge is the largest series of patients with cT1 micropapillary bladder cancer.

MATERIALS AND METHODS

An institutional review board approved review of our cancer database identified 283 patients with micropapillary bladder cancer, including 72 staged with cT1N0M0 disease at diagnosis and initiation of therapy. Survival analysis was performed using the Kaplan-Meier estimator and compared using the log rank test.

RESULTS

In this cohort of 72 patients 40 received primary intravesical bacillus Calmette-Guérin and 26 underwent up-front radical cystectomy. Of patients who received bacillus Calmette-Guérin 75%, 45% and 35% experienced disease recurrence, progression and lymph node metastasis, respectively. Patients treated with up-front cystectomy had improved survival compared to patients treated with primary bacillus Calmette-Guérin (5-year disease specific survival 100% vs 60% p = 0.006) and patients who underwent delayed cystectomy after recurrence (5-year disease specific survival 62%, p = 0.015). Prognosis was especially poor in patients who waited for progression before undergoing radical cystectomy with an estimated 5-year disease specific survival of only 24% and a median survival of 35 months. In patients treated with up-front cystectomy pathological up-staging was found in 27%, including 20% with lymph node metastasis.

CONCLUSIONS

While certain patients with T1 micropapillary bladder cancer may respond to intravesical bacillus Calmette-Guérin, survival is improved in those who undergo early radical cystectomy. Further molecular studies are needed to identify subsets of patients in whom the bladder can be safely spared.

Micropapillary bladder cancer: current treatment patterns and review of the literature

OBJECTIVES

No guidelines exist for the management of micropapillary bladder cancer (MPBC) and most reports of this variant of urothelial carcinoma are case series comprising small numbers of patients. We sought to determine current practice patterns for MPBC using a survey sent to the Society of Urologic Oncology (SUO) and to present those results in the setting of a comprehensive review of the existing literature.

MATERIALS AND METHODS

A survey developed by the Translational Science Working Group of the Bladder Cancer Advocacy Network-sponsored Think Tank meeting was distributed to members of the SUO. The results from 118 respondents were analyzed and presented with a literature review.

RESULTS

Most survey respondents were urologists, with 80% considering bladder cancer their primary area of interest. Although 78% of the respondents reported a dedicated genitourinary pathologist at their institution, there were discrepant opinions on how a pathologic diagnosis of MPBC is determined as well as variability on the proportion of MPBC that is clinically significant. Among them, 78% treat MPBC differently than conventional urothelial carcinoma, with 81% reporting that they would treat cT1 MPBC with upfront radical cystectomy. However, the respondents had split opinions regarding the sensitivity of MPBC to cisplatin-based chemotherapy, which affected utilization of neoadjuvant chemotherapy in muscle-invasive disease.

CONCLUSIONS

The management of MPBC is diverse among members of the SUO. Although most favors early cystectomy for cT1 MPBC, there is no consensus on the use of neoadjuvant chemotherapy for muscle-invasive MPBC.

Outcome of patients with micropapillary urothelial carcinoma following radical cystectomy: ERBB2 (HER2) amplification identifies patients with poor outcome

Micropapillary urothelial carcinoma exhibits amplification of the human epidermal growth factor receptor, ERBB2(HER2), and overexpression of the ERBB2 protein product. The clinical significance of this has yet to be established. The objective of this study was to examine ERBB2 amplification and protein expression in micropapillary urothelial carcinoma and stage-matched typical urothelial carcinoma treated by radical cystectomy to assess the frequency of amplification and protein expression, and to determine the association with cancer-specific survival. Pathologic material and data from patients undergoing cystectomy at Mayo Clinic between 1980 and 2008 were reviewed. ERBB2 amplification by fluorescence in situ hybridization (FISH) and protein expression by immunohistochemistry were assessed. Univariate and multivariate Cox proportional hazards regression models were used to evaluate for associations of ERBB2 amplification and protein expression with survival. ERBB2 amplification was identified in 9 (15%) of 61 micropapillary carcinomas compared with 9 (9%) of 100 urothelial carcinomas. In patients with micropapillary carcinoma, ERBB2 amplification was associated with a nearly threefold increased risk of cancer death. ERBB2 amplification (hazard ratio 4.3; P=0.0008) remained associated with an increased risk of death from bladder cancer among patients with micropapillary urothelial carcinoma on multivariate analysis. The association of cancer-specific survival and ERBB2 amplification was not seen in patients with urothelial carcinoma. ERBB2 immunohistochemistry correlated with ERBB2 amplification but there was no association of ERBB2 protein expression and survival. ERBB2 amplification is more frequent in micropapillary urothelial carcinoma than typical urothelial carcinoma, and patients with micropapillary carcinoma who have ERBB2 amplification have worse cancer-specific survival than those who do not. Identification of ERBB2 amplification in micropapillary carcinoma could provide important prognostic information and possibly provide a role for ERBB2 targeted therapy.