Transurethral Resection Specimens of the Bladder: Outcome of Invasive Urothelial Cancer Involving Muscle Bundles Indeterminate Between Muscularis Mucosae and Muscularis Propria

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.

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.

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.

Clinicopathologic characterization of intradiverticular carcinoma of urinary bladder - a study of 22 cases from a single cancer center

Background

To examine histopathologic features and clinical outcomes of intradiverticular bladder carcinomas.

Methods

Twenty-two consecutive patients with intradiverticular bladder carcinoma treated with either endoscopic transurethral resection or partial or radical cystectomy at a single institution between years of 1995 to 2011. Clinicopathologic characteristics and oncologic outcomes of patients were retrospectively analyzed, including tissue histology re-review by genitourinary pathologists.

Results

Histologically, 9 cases (41%) were non-invasive papillary urothelial carcinoma, 13 cases (59%) were invasive urothelial carcinoma, including three cases of small cell carcinoma. Final pathology revealed synchronous extradiverticular urothelial carcinomas in 6 out of 9 cases (67%) of non-invasive and 2 out of 10 cases (20%) invasive intradiverticular urothelial carcinoma, respectively. More than half of cases (13/22, 59%) showed a distinctive hypertrophic layer of muscularis mucosae. There was no statistical difference in disease free survival or overall survival between non-invasive and invasive tumors within approximately 3 years of follow up (mean 38 months, median 32 months). While stage T3 patients generally did poorly, oncologic outcomes for stage T1 patients were no different than those of stage Ta.

Conclusion

Intradiverticular carcinomas are often associated with a hypertrophic layer of muscularis mucosae that can potentially confound tumor staging. Non-invasive intradiverticular urothelial carcinomas are more likely to have coexisting synchronous extradiverticular lesions. The absence of a muscularis propria layer may not necessarily predispose T1 tumors to more aggressive disease.

Virtual Slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_222

Restaging transurethral resection for non-muscle invasive bladder cancer: who, why, when, and how?

The rate of clinical understaging in non-muscle invasive bladder cancer (NMIBC) after an initial transurethral resection (TUR) is significant, particularly for high-grade disease, and this has a major impact on prognosis. A repeat TUR, 2 to 6 weeks following the initial resection, is recommended in appropriately selected cases to avoid diagnostic inaccuracy and improve treatment allocation. This article summarizes the rationale and indications for performing a repeat TUR in NMIBC and also provides information regarding patient selection and technique.

ICUD-EAU International Consultation on Bladder Cancer 2012: Pathology

CONTEXT

To present a summary of the 2nd International Consultation on Bladder Cancer recommendations on the pathology of bladder cancer using an evidence-based strategy.

OBJECTIVE

To standardize descriptions of the diagnosis and reporting of urothelial carcinoma of the bladder and help optimize uniformity between individual pathology practices and institutions.

EVIDENCE ACQUISITION

A detailed Medline analysis was performed for original articles addressing bladder cancer with regard to pathology. Proceedings from the last 5 yr of major conferences were also searched.

EVIDENCE SYNTHESIS

The major findings are presented in an evidence-based fashion. Large retrospective and prospective data were analyzed.

CONCLUSIONS

Providing the best management for patients with bladder neoplasia relies on close cooperation and teamwork among urologists, oncologists, radiologists, and pathologists.