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ERUS 2018: How to Manage Histological Variants Of Bladder Cancer? Pathological Aspect

Marseille, France (UroToday.com) An overview of the pathological aspects of variant histology (VH) of bladder cancer was given by Dr. Eva Comperat.  It is important to recognize and report these VHs and discuss the interobserver variability, tumor heterogeneity and treatment decisions for these unique tumors.

According to the WHO classification of tumors of the urothelial tract, urothelial tumors include:

  • Infiltrating urothelial carcinomas with divergent differentiation
  • Nested, include largely nested
  • Microcystic
  • Micropapillary
  • Lymphoepithelioma-like
  • Diffuse/Plasmacytoid/Signet ring cell
  • Sarcomatoid
  • Giant Cell
  • Undifferentiated
  • Lipid-rich
  • Clear cell
VH is underrecognized, according to a study published in 20131.  Out of 589 TURBTs, 19.5% had VH with 90% having one VH. According to this report, several types of VH were unrecognized.  One of the problems of VH is that there is significant discordance among pathologists, with 93% agreement on classic forms, but a much lower percentage reported for less common forms.

There is also some data showing that TURBT might not sufficiently show VH, even though it will eventually show up in radical cystectomy specimens of the same patients. It is not clear if this is because of tumor heterogeneity or small samples taken in the TURBTs.

The next topic discussed was the VH of micropapillary carcinoma. In a study analyzing cT1N0M0 micropapillary carcinoma patients, those who were treated with upfront radical cystectomy had a disease-specific survival of 100%, while those who were first treated with BCG had a recurrence in 75% of cases, and 45% of them had disease progression2. Additionally, those treated with delayed radical cystectomy had a disease-specific survival of only 62%, so the timing of therapy is also crucial2. Early identification of this specific variant and performance of radical cystectomy as soon as possible will save patient lives.

Next, Dr. Comperat discussed the molecular characterization of muscle-invasive bladder cancer3. This characterization has a significant impact on the opportunity for immunological therapy, as it enables us to understand which cancer might respond well to immune therapy (Figure 1).

UroToday ERUS2018 Molecular characterization of muscle invasive bladder cancer
Figure 1 – Molecular characterization of muscle-invasive bladder cancer:

In conclusion, VH is important to recognize and report as the implication on the therapy choices and outcomes are tremendous. Unfortunately, these are still under-recognized and underreported tumors, and there is a large discordance rate between pathologists on VH diagnosis. Furthermore, tumor heterogeneity is still a significant problem that needs to be dealt with, and in the future, the incorporation of molecular data could help us treat these patients appropriately.

Presented by: Eva Compérat, Paris, France

Written by: Hanan Goldberg, MD, Urologic Oncology Fellow (SUO), University of Toronto, Princess Margaret Cancer Centre, Twitter:@GoldbergHanan at the EAU Robotic Urology Section (ERUS) Meeting - September 5 - 7, 2018 - Marseille, France

References:

  1. Shah RB, Montgomery JS, Montie JE, et al. Variant (divergent) histologic differentiation in urothelial carcinoma is under-recognized in community practice: impact of mandatory central pathology review at a large referral hospital. Urologic oncology 2013; 31(8): 1650-5.
  2. Willis DL, Fernandez MI, Dickstein RJ, et al. Clinical outcomes of cT1 micropapillary bladder cancer. The Journal of Urology 2015; 193(4): 1129-34.
  3. Robertson AG, Kim J, Al-Ahmadie H, et al. Comprehensive Molecular Characterization of Muscle-Invasive Bladder Cancer. Cell 2018; 174(4): 1033.
Further Related Content: 
How to Manage Histological Variants of Bladder Cancer? Clinical Consequences