Rare tumours of the bladder: A Saudi registry based descriptive study.

Objective: There is limited literature focusing on the characteristics and behaviours of bladder tumours outside of the common three morphologies, that is, urothelial carcinoma, squamous cell carcinoma, and adenocarcinoma. The presented study provides a descriptive analysis of rare bladder tumours in KSA. Methods: This retrospective cohort study included all patients with a primary rare bladder tumour between 1 January 2008 and 31 December 2017. The data were acquired from the Saudi Tumour Registry. Frequencies and percentages were then generated for the categorical variables, while means and standard deviations were calculated for quantitative variables. Results: The study included 65 patients. The majority (n = 35, 53.8%) were aged 60 years and older. The patients were predominantly male (n = 53, 81.5%) and the majority lived in the Western region (n = 26, 40.?%). The most diagnosed tumour morphologies were small cell carcinoma in adults (n = 11, 16.9%) and embryonal rhabdomyosarcoma in children (n = 14, 21.5%), with the dominant diagnosis method being histology of primary tumour in 98.5% of the patients. Most tumours were localised (n = 30, 46.2%) and multifocal (n = 34, 52.3%). The overall mortality rate was 24.6%, with an overall diagnosis to death interval of 1.14 ± 0.75 years wherein small cell carcinoma was the shortest (0.84 ± 0.24) days. Conclusion: There remains a gap in the literature regarding uncommon urologic tumours. Shedding light on these factors will aid in further understanding the patterns of tumour behaviour in the region. This will facilitate enhanced risk-and response-based screening strategies and more favourable outcomes. Additionally, formulating a global registry for such patients is recommended.