Non-urothelial and urothelial variants of bladder cancer

Non-urothelial bladder cancers make up a rare minority of all genitourinary (GU) tract histologic cancers since urothelial cancer (UC) makes up the most common histologic subtype. Bladder cancer variant histology (BCVH) or urothelial variants also occur rarely though distinction is important given aggressive presentation and natural history. While methods for diagnosis and treatment of typical urothelial cancers (UC) are well-established, there are no clear guidelines with regard to the diagnosis of non-urothelial bladder cancers, which often results in misdiagnosis and treatment delay. This review will focus on the clinicopathologic characteristics of the most common non-urothelial bladder cancers, to be distinguished from bladder cancer variant histology containing a UC component. The role of genomics in non-urothelial bladder cancers is evolving and the use of biomarkers to guide the diagnosis and treatment of these tumors remains a key area of unmet need. Treatment of these cancers will be discussed in a companion review.

Genomic characterization of non-schistosomiasis-related squamous cell carcinoma of the urinary bladder: A retrospective exploratory study

Background

Non-schistosomiasis related-squamous cell carcinoma of urinary bladder (NSR-SCCUB) is a rare tumor subtype distinct from urothelial carcinoma (UC). Studies assessing molecular biomarkers in bladder cancer have generally focused on UC, and genomic data of NSR-SCCUB is limited. We aim to provide additional insight into the molecular underpinnings of this rare entity.

Methods

NSR-SCCUB patients were identified retrospectively at Princess Margaret Cancer Centre between 2002 and 2017. Demographics, disease characteristics, therapeutic approaches, and outcomes were collected. Tissue samples were interrogated using the Oncomine Comprehensive Assay v3 (ThermoFisher). Kaplan-Meier method was used to estimate the disease-free survival and overall survival (OS).

Results

Overall, 11 patients with NSR-SCCUB were identified between 2002 and 2017 with adequate tissue samples. Median age was 71 years (45–86), predominantly male (63.6%). At time of diagnosis, 9 patients (81.8%) had muscle-invasive disease, 1 (9.1%) had non-muscle invasive, and 1 (9.1%) had advanced disease. Nine (81.8%) patients had radical cystectomy and pelvic lymph nodes dissection. Eight (72.7%) patients had pT3 or pT4 with N0, and 5 (45.5%) were grade 3. Median OS was 12.5 months (95% CI 7.7–17.2 months). Single nucleotide variants or insertion/deletions were identified in TP53, TERT, PIK3CA, PTEN, CREBBP, FBXW7, and FGFR3. Amplifications were found in CCND1, and EGFR.

Conclusions

NSR-SCCUB has potentially actionable genomic alterations with anticancer agents and many of these aberrations are also seen in UC. The recruitment of NSR-SCCUB patients harboring such mutations should be considered in biomarker driven urinary bladder cancer studies.