Pitfalls in the Use of Smoothelin to Identify Muscularis Propria Invasion by Urothelial Carcinoma

The Impact of Second Opinion Expert Pathology Review in Patient Management at the Time of Transurethral Resection of the Bladder

BACKGROUND AND OBJECTIVE

Pathological features in non-muscle-invasive bladder cancer specimens are pivotal in determining correct patients' therapeutic management. Sparse data exist regarding the importance of second opinion performed by an expert uropathologist. This study aimed to assess the importance of a second opinion by an expert uropathologist in the management of bladder cancer.

METHODS

The study relied on 272 bladder cancer specimens from 231 patients seeking a pathology second opinion after transurethral resection of the bladder for a clinical suspicion of bladder cancer, relapse, or second-look procedure. Pathology second opinion was offered by an experienced fellowship-trained uropathologist. Discrepancies were recorded considering primary tumor staging, the presence of muscularis propria, and the presence of histological variants. Cases were categorized as no significant discordance, major discordance without management change, and major discordance with management change according to the European Urology Association (EAU) guidelines.

KEY FINDINGS AND LIMITATIONS

Among 272 second opinion cases, 39% (108/272) had major discordance and 28% (75/272) had major discordance with change in management according to the EAU guidelines. Upstaging and downstaging were reported in 66 (24%) patients. Improper identification of the presence of muscularis propria was found in 46 (17%) cases, of which 11 (4%) were deemed clinically relevant. Differences regarding the presence of histological variants were diagnosed in 40 cases (15%), resulting in eight (3%) changes in clinical management. In ten specimens (4%), multiple clinically relevant discrepancies were found.

CONCLUSIONS AND CLINICAL IMPLICATIONS

The second opinion evaluation changed the clinical management in 25% of the cases. These results support the importance of specimen review by an expert uropathologist as a major driver in the correct bladder cancer management.

PATIENT SUMMARY

We investigated the importance of a second opinion performed by an expert uropathologist in the management of bladder cancer. We found that 25% had their treatment plan changed due to the revised pathological report.

Usefulness of COL11A1 as a Prognostic Marker of Tumor Infiltration

BACKGROUND

Determining the infiltration of carcinomas is essential for the proper follow-up and treatment of cancer patients. However, it continues to be a diagnostic challenge for pathologists in multiple types of tumors. In previous studies (carried out in surgical specimens), the protein COL11A1 has been postulated as an infiltration marker mainly expressed in the extracellular matrix (ECM). We hypothesized that a differential expression of COL11A1 may exist in the peritumoral stroma of tumors that have acquired infiltrating properties and that it may be detected in the small biopsies usually available in normal clinical practice.

MATERIAL AND METHODS

In our study, we performed immunohistochemical staining in more than 350 invasive and noninvasive small samples obtained via core needle biopsy (CNB), colonoscopy, or transurethral resection of bladder tumor (TURBT) of breast, colorectal, bladder, and ovarian cancer.

RESULTS

Our results revealed that COL11A1 immunostaining had a sensitivity to classify the samples into infiltrative vs. noninfiltrative tumors of 94% (breast), 97% (colorectal), >90% (bladder), and 74% (ovarian); and a specificity of 97% (breast), 100% (colorectal), and >90% (bladder). In ovarian cancer, the negative predictive value (0.59) did not present improvement over the usual histopathological markers. In all samples tested, the cumulative sensitivity was 86% and the specificity 96% (p < 0.0001).

CONCLUSIONS

COL11A1-positive immunostaining in small biopsies of breast, colon, bladder and ovarian cancer is an accurate predictive marker of tumor infiltration that can be easily implemented in daily clinical practice.

Deep learning for histopathological segmentation of smooth muscle in the urinary bladder

BACKGROUND

Histological assessment of smooth muscle is a critical step particularly in staging malignant tumors in various internal organs including  the urinary bladder. Nonetheless, manual segmentation and classification of muscular tissues by pathologists is often challenging. Therefore, a fully automated and reliable smooth muscle image segmentation system is in high demand.

METHODS

To characterize muscle fibers in the urinary bladder, including muscularis mucosa (MM) and muscularis propria (MP), we assessed 277 histological images from surgical specimens, using two well-known deep learning (DL) model groups, one including VGG16, ResNet18, SqueezeNet, and MobileNetV2, considered as a patch-based approach, and the other including U-Net, MA-Net, DeepLabv3 + , and FPN, considered as a pixel-based approach. All the trained models in both the groups were evaluated at pixel-level for their performance.

RESULTS

For segmenting MP and non-MP (including MM) regions, MobileNetV2, in the patch-based approach and U-Net, in the pixel-based approach outperformed their peers in the groups with mean Jaccard Index equal to 0.74 and 0.79, and mean Dice co-efficient equal to 0.82 and 0.88, respectively. We also demonstrated the strengths and weaknesses of the models in terms of speed and prediction accuracy.

CONCLUSIONS

This work not only creates a benchmark for future development of tools for the histological segmentation of smooth muscle but also provides an effective DL-based diagnostic system for accurate pathological staging of bladder cancer.

Stage T1 bladder cancer: diagnostic criteria and pitfalls

Accurate pathological staging is crucial for patient management. Patients with T1 bladder cancer are at risk of recurrence, progression, and death of cancer. Recognition of early invasion (stage T1 disease) in urothelial carcinoma remains one of the most challenging areas in urological surgical pathology practice. A logical roadmap to T1 diagnosis would include careful evaluation of histological grade, stromal epithelial interface, characteristics of the invading epithelium, and the stroma associated responses. Tangential sectioning, crush and cautery artifacts, and associated inflammatory infiltrate are commonly encountered problems and the source of pitfalls. In this review, we outline diagnostic criteria, common pitfalls, and different histological patterns of invasion into the lamina propria. Current recommendations on reporting of biopsy and transurethral resection specimens, molecular biomarkers, clinical implications of T1 cancer diagnosis and recent developments on the T1 substaging are also discussed. Most T1 bladder cancer patients will benefit from conservative management after restaging transurethral resection of bladder and bacillus Calmette-Guérin maintenance. Patients with high risk features, such as concurrent urothelial carcinoma in situ, increased depth of invasion, lymphovascular invasion, and variant histology among others, should be considered for early cystectomy.

Analysis of Tumor Depth Invasion With Anti-Smoothelin Antibody in Equivocal Transurethral Resection of Urinary Bladder Tumor Surgical Specimens

OBJECTIVE

To examine the expression and value of the smoothelin marker in control cases, to standardize the working method, and to analyze its application in pathologic staging process of problematic transurethral resection of bladder tumor (TURBT) cases.

MATERIAL AND METHODS

Immunohistochemical (IHC) staining was performed on tumor-free bladder wall sections, tumor-free large bowel sections, TURBTs with unequivocal tumor stage, and TURBTs with equivocal stage. The IHC staining of muscularis mucosa (MM), muscularis propria (MP), and blood vessels was evaluated semiquantitatively.

RESULTS

Smoothelin IHC staining pattern ranged from negative (30% to 67% cases) to 2+ (0% to 15% cases) in MM and from 1+ (10% to 50% cases) to 3+ (9% to 48% cases) in MP. When compared on the same slide, the smoothelin expression of MP showed a stronger staining intensity than the one of the MM in all the analyzed cases. Blood vessel muscle cells stained in a constant intensity as the MM (r = 0.9808; r = 0.9604). Smoothelin determined restaging of 33% of the problematic TURBT cases.

CONCLUSION

Smoothelin is an IHC marker that shows differential staining between coexistent MM and MP; however, variations in staining intensity and pattern may occur, aspects that can be influenced by different technique variables. We recommend using this marker as a diagnostic tool in problematic TURBT cases only when there is sufficient experience in control cases with this antibody.

Bladder Cancer Involving Smooth Muscle of Indeterminate Type or Muscularis Mucosae in Transurethral Biopsy Specimens

OBJECTIVES

Bladder cancers invading the muscularis mucosae (MM) are treated differently from those invading the muscularis propria (MP). However, it may be difficult to determine the type of smooth muscle in transurethral resection (TUR) or biopsy specimens. We aimed to investigate the clinicopathologic features of bladder cancers involving smooth muscle of indeterminate type (SMIT) in TUR specimens in comparison with those invading the MM.

METHODS

We identified 103 patients with bladder cancer involving SMIT (n = 27) or the MM (n = 76) in TUR specimens. All patients underwent subsequent restaging TUR or cystectomy.

RESULTS

Bladder cancer with SMIT invasion showed a significantly higher rate of MP invasion in the subsequent specimens than those invading the MM (52% vs 29%). Lack of MP in the TUR specimens had a significantly higher risk of MP invasion in the subsequent specimens than those with the MP (61% vs 40%). The overall survival time for patients with SMIT invasion was significantly shorter than those with MM invasion.

CONCLUSIONS

Bladder cancers with SMIT invasion in TUR specimens show more frequent cancer upstaging in the subsequent specimens and a poorer clinical outcome than those invading the MM, which highlights the importance of a cancer restaging procedure for these patients.

pT1 high-grade bladder cancer: histologic criteria, pitfalls in the assessment of invasion, and substaging

Most patients with bladder carcinoma are diagnosed with non-muscle-invasive disease, stage Ta, and pT1. Stage remains as the single most important prognostic indicator in urothelial carcinoma. Among the pT1 bladder cancer patients, recurrence and progression of disease occur in 50% and 10%, respectively. The identification of high-risk patients within the pT1 subgroup remains an important clinical goal and an active field of research. Substaging of pT1 disease has been claimed as important histologic discriminator by the 2016 World Health Organization (WHO) classification of the genitourinary tract tumors and by the 8th edition of the American Joint Committee on Cancer (AJCC) staging manual supporting its implementation in clinical practice. Interobserver variation in pT1 diagnosis and the associated pitfalls in pT1 assessment are the critical pathological issues. The aim of this review paper is to provide the practicing pathologist with the state of the art of morphological and immunohistochemical features useful for the diagnosis of early invasive bladder carcinomas, including practical clues on how to avoid relevant interpretative pitfalls, and to summarize the current status of pT1 substaging.

Dataset for the reporting of urinary tract carcinoma-biopsy and transurethral resection specimen: recommendations from the International Collaboration on Cancer Reporting (ICCR)

The International Collaboration on Cancer Reporting (ICCR) is an alliance of major pathology organisations in Australasia, Canada, Europe, United Kingdom, and United States of America that develops internationally standardised, evidence-based datasets for the pathology reporting of cancer specimens. This dataset was developed by a multidisciplinary panel of international experts based on previously published ICCR guidelines for the production of cancer datasets. It is composed of Required (core) and Recommended (noncore) elements identified on the basis of literature review and expert consensus. The document also includes an explanatory commentary explaining the rationale behind the categorization of individual data items and provides guidance on how these should be collected and reported. The dataset includes nine required and six recommended elements for the reporting of cancers of the urinary tract in biopsy and transurethral resection (TUR) specimens. The required elements include specimen site, operative procedure, histological tumor type, subtype/variant of urothelial carcinoma, tumor grade, extent of invasion, status of muscularis propria, noninvasive carcinoma, and lymphovascular invasion (LVI). The recommended elements include clinical information, block identification key, extent of T1 disease, associated epithelial lesions, coexistent pathology, and ancillary studies. The dataset provides a structured template for globally harmonized collection of pathology data required for management of patients diagnosed with cancer of the urinary tract in biopsy and TUR specimens. It is expected that this will facilitate international collaboration, reduce duplication of effort in updating current national/institutional datasets, and be particularly useful for countries that have not developed their own datasets.

Clinical significance of urothelial carcinoma ambiguous for muscularis propria invasion on initial transurethral resection of bladder tumor

PURPOSE

To evaluate the clinical significance of invasive urothelial carcinoma that is ambiguous for muscularis propria invasion on initial transurethral resection of bladder tumor (TURBT).

METHODS

All consecutive in-house TURBTs with invasive urothelial carcinoma from 1999 to 2017 that underwent radical cystectomy (RC) were grouped as follows: invasion of the lamina propria (INLP; n = 102; 24%), invasion of muscularis propria (INMP; n = 296; 69%) and ambiguous for muscularis propria invasion (AMP; n = 30; 7%). AMP was defined as extensive invasive carcinoma displaying thin muscle bundles where it is difficult to determine with certainty if those muscle bundles represent muscularis mucosae or muscularis propria (detrusor). Cases with any amount of small cell carcinoma or prior therapy were excluded.

RESULTS

The average age was 66 years in INLP, 67 years in INMP, and 65 years in AMP. RC showed invasive carcinoma stage pT2 or above in 50/102 (49%) of INLP vs. 255/296 (86%) of INMP (P ≤ 001) vs. 25/30 (83.33%) of AMP (P = 0.002). Lymph nodes showed metastatic carcinoma in 18/98 (18.36%) of INLP vs. 96/272 (35.29%) of INMP (P = 0.002), and 6/25 (24%) in AMP (P = 0.729). The average follow-up was 48 months (range 0-192). Survival of AMP patients was similar to INLP and both were significantly better than INMP (P = 0.002 and P = 0.016).

CONCLUSION

The great majority of patients with AMP on initial TURBT have advanced disease on RC and emphasizes the need for early repeat TURBT or even consideration of early cystectomy to lower the risk of worse pathological findings and to prolong survival.

Contemporary Grading and Staging of Urothelial Neoplasms of the Urinary Bladder: New Concepts and Approaches to Challenging Scenarios

Grading and staging of urothelial neoplasm are the most crucial factors in risk stratification and management; both necessitate optimal accuracy and consistency. Several updates and recommendations have been provided though recent publications of the 4th edition of the World Health Organization classification, the 8th edition of the American Joint Committee on Cancer staging system, and the International Consultation on Urological Diseases-European Association of Urology updates on bladder cancer. Updates and recent studies have provided better insights into and approaches to the challenging scenarios in grading and staging of urothelial neoplasm; however, there remain aspects that need further investigation and refinement.

Contribution of bladder cancer pathology assessment in planning clinical trials

Bladder cancer is a heterogeneous disease that demonstrates a wide spectrum of histologic features. The modern classification of bladder cancer is largely based on pathologic analysis, which assesses tumor grade, stage, type, size, and other features that are essential for understanding the biological behavior of bladder cancer. Bladder cancers with similar histologic features are likely to show comparable responses to a new therapeutic agent in clinical trial. Furthermore, pathologic analysis also evaluates the quality of tissue samples in clinical trial to ensure the integrity of various molecular tests. In spite of the emerging role of genomic and molecular studies, pathology remains the cornerstone in the diagnosis, prognosis, and treatment of bladder cancer. Herein, the pathologic considerations for bladder cancer clinical trial planning are reviewed.

Practical Applications of Immunohistochemistry in the Diagnosis of Genitourinary Tumors

Context.—

Pathologic diagnosis of tumors in the genitourinary system can be challenging based on morphology alone, particularly when diagnostic material is limited, such as in core biopsies. Immunohistochemical stain can be a useful tool to aid in the diagnosis.

Objective.—

To provide an update on practical applications and interpretation of immunohistochemical stains in the diagnosis of tumors in prostate, kidney, bladder, and testis. We particularly focus on difficult differential diagnoses, providing our insights in frequently encountered challenging situations. Commonly used immunohistochemical panels are discussed.

Data Sources.—

Review of literature and our own experience.

Conclusion.—

Immunohistochemical stain is a valuable tool in the diagnosis of genitourinary tumors when appropriately used.

Diagnostic Value of Smoothelin and Vimentin in Differentiating Muscularis Propria from Muscularis Mucosa of Bladder Carcinoma

Background

Determination of the extent of involvement or pathological staging is one of the requirements for adequate evaluation of bladder cancer specimens. Therefore, the differentiation between MP and MM is essential for proper treatment and avoiding over or under staging.

Aim

The present study aimed at evaluation of diagnostic value of smoothelin and vimentin expression both singly and in combination for differentiation between MM and MP.

Methods

This study was carried out on 59 cystectomy specimens of primary bladder carcinoma and eleven cystoscopic biopsies for non-neoplastic bladder lesions (cystitis).

Results

Histologically, MM was identified clearly in 40 cases and MP was identified in all 70 examined cases. The cases were immunostained for smoothelin and vimentin. Intensity of smoothelin expression showed significant difference (P = 0.001) between MM and MP with 97.5% sensitivity and 95% specificity and the percentage of smoothelin expression was significantly higher in MP compared to MM (P = 0.001) with 95.7% sensitivity and 85% specificity (using 65% as cut-off point). Vimentin was negative in MP and showed positive expression in 32 cases (80%) of MM with a statistical significant difference (P = 0.001) providing 80% sensitivity and 100% specificity. Combined moderate to strong smoothelin and negative vimentin offered 100% sensitivity and 100% specificity towards the identification of MP.

Conclusions

Differentiation of MM from MP can be made based on histopathological criteria, which are unfortunately overlapping in many cases. Moderate to strong smoothelin expression with negative vimentin could be very helpful procedure in difficult and overlapping cases with a high diagnostic validity.

Challenges in Pathologic Staging of Bladder Cancer: Proposals for Fresh Approaches of Assessing Pathologic Stage in Light of Recent Studies and Observations Pertaining to Bladder Histoanatomic Variances

The paradigm of pathologic stage (pT) categorization in bladder cancer remains the depth of invasion into the different histologic layers of the bladder wall. However, the approaches to assigning pT stage category toward an enhanced outcome stratification have been marked by challenges and innovations, due in part to our growing appreciation of the surprisingly perplexing bladder histoanatomy. Upstaging of pT1 tumors after radical cystectomy is substantial and underscores the potential value of pT1 substaging in transurethral resection (TUR) specimens. The 2017 American Joint Committee on Cancer tumor-node-metastasis system recommends pT1 substaging but recognizes the need to optimize the approach. Over the years, the cut-off for microinvasion has been significantly lowered to 0.5 mm and is now a promising scheme for pT1 (micrometric) substaging. Unlike the micrometric approach, histoanatomic substaging using muscularis mucosae (MM) and vascular plexus as landmarks is less feasible in TUR specimens and inconsistent in stratifying the outcome of pT1 tumors. The lamina propria possesses inherent variations in depth, MM, and vascular plexus dispositions that should be factored in future pT1 substaging proposals. Histoanatomic variations among the bladder regions also occur, and studies suggest that trigone and bladder neck cancers may have more adverse outcomes. The muscularis propria (MP), besides being the essential histologic landmark for assigning pT2 stage category, is also considered a surrogate for the adequacy of TUR, furthering the importance of identifying its presence in TUR specimens. MP, however, may be mimicked by hyperplastic or isolated MP-like MM muscle bundles in the lamina propria with overstaging implications, and caution should be exercised in distinguishing these 2 muscle types morphologically and immunohistochemically. Presence of additional superficial MP unique from the detrusor muscle proper may also complicate staging at the trigone and ureter insertion sites. With regard to the depth of MP invasion, large and multicenter studies have reaffirmed the prognostic significance of pT2a/b subcategories. It is revealed that there are at least 3 ways used to demarcate the irregular MP to perivesical soft tissue junction, and use of a common criterion indicates improvement in pT2b/pT3a staging reproducibility. Although studies have shown significantly poorer outcome in pT3b compared with pT3a tumors, this designation has a substantial reliance on the prosector's gross assessment of perivesical soft tissue invasion which if performed incorrectly may lead to staging inaccuracy of pT3 tumors. The 8th edition of the American Joint Committee on Cancer has updated the staging schema for bladder cancers with concomitant prostatic stromal invasion and cancers within bladder diverticula. Because of 2 possible pT designations, prostatic stromal invasion in TUR specimens should not be automatically staged as either pT4a or pT2 (urethral). Recent data support that bladder cancer invading into the seminal vesicle has comparable outcome to pT4b tumors. Interestingly, several studies in pT4a tumors, which are staged based on sex-specific organs, have shown poorer outcome in females than males after radical cystectomy, and while there are possibly several reasons, they may also include anatomic factors. Despite the progress has been made, work remains to be done to inform future bladder cancer pT category definitions and their reproducibility in application and prognostication.

Bladder cancer

Bladder cancer is a complex disease associated with high morbidity and mortality rates if not treated optimally. Awareness of haematuria as the major presenting symptom is paramount, and early diagnosis with individualised treatment and follow-up is the key to a successful outcome. For non-muscle-invasive bladder cancer, the mainstay of treatment is complete resection of the tumour followed by induction and maintenance immunotherapy with intravesical BCG vaccine or intravesical chemotherapy. For muscle-invasive bladder cancer, multimodal treatment involving radical cystectomy with neoadjuvant chemotherapy offers the best chance for cure. Selected patients with muscle-invasive tumours can be offered bladder-sparing trimodality treatment consisting of transurethral resection with chemoradiation. Advanced disease is best treated with systemic cisplatin-based chemotherapy; immunotherapy is emerging as a viable salvage treatment for patients in whom first-line chemotherapy cannot control the disease. Developments in the past 2 years have shed light on genetic subtypes of bladder cancer that might differ from one another in response to various treatments.

Morphologic and Molecular Characteristics of Bladder Cancer

Bladder cancer is the fourth most common cancer in men, and is associated with significant morbidity and mortality. Pathologic evaluation of urothelial cancers relies predominantly on histomorphologic features but can be aided in a small subset of cases by immunohistochemical analyses. Distinction of papillary versus flat lesions, low-grade versus high-grade cytology, and histologic variants and the presence or absence of invasive tumor is important for proper clinical management. Advances in the molecular alterations associated with the various subtypes of urothelial carcinoma have been made but such studies are ongoing.

Down-staging (<pT2) of urothelial cancer at cystectomy after the diagnosis of detrusor muscle invasion (pT2) at diagnostic transurethral resection (TUR): is prediction possible?

Urothelial cell carcinoma (UCC) with musculus detrusor (MD) invasion is treated by cystectomy. Subsequent pathologic evaluation of cystectomies does not reveal MD invasion (<pT2) in a subgroup of patients. Our objective was to identify features at diagnostic transurethral resection (TUR) predicting down-staging (<pT2) at cystectomy. Patients with pathologically confirmed MD invasion at TUR followed by cystectomy for UCC without (neo-) adjuvant therapy were included (N = 106). Slides of both TUR and cystectomy specimens were reviewed, and survival analyses were performed. In total, 27/106 (26 %) tumors were down-staged at cystectomy, of which 13 (12 %) had no residual tumor (pT0). There was no significant difference in age, gender, time interval between TUR and operation, number of slides sampled, and presence of TUR scar between down-staged (<pT2) and pT2 UCC. At review of TUR specimens (N = 52) with UCC initially diagnosed as pT2, MD invasion was not confirmed in eight cases (15 %). One case showed extensive histiocytic reaction misinterpreted as UCC; in four cases, muscularis mucosae had been considered MD, and in three cases, desmoplastic reaction mimicked MD. No histologic parameter at TUR was significantly associated with down-staging at cystectomy. Overall and disease-specific survival was not statistically different in down-staged and pT2 UCC. In conclusion, down-staging of UCC (<pT2) at cystectomy occurred in 26 %. At review of diagnostic TURs, MD invasion was not confirmed in 15 %. No clinical or pathologic parameter was predictive for down-staging at cystectomy. There was no difference in survival between down-staged and pT2-staged UCC.