Urinary Bladder Sinuses

Abstract

We described urinary bladder sinuses (UBS) in the urinary bladder, characterized by segmental mucosal with muscularis mucosa invaginations into the submucosa (superficial UBS) and muscularis propria (deep UBS). Radical cystectomy specimens and transurethral resections of the bladder were reviewed. Superficial UBS (extending up to the submucosa) were distinguished from cystitis cystica, and deep UBS differed from embryonic remnants, intramural ureters, and diverticulum by their cleft-like structures lined by the urothelium. In transurethral resections of the bladder specimens and bladder biopsy specimens, superficial UBS were identified in 13/20 cases. In radical cystectomy specimens, superficial UBS were identified in 15/50 cases, whereas deep UBS (all with associated superficial UBS) were seen in 23/50 additional cases. Deep UBS limited to the inner quarter of the muscularis propria and only reached the level of the inner third outer/middle third of the muscularis propria in 5 cases. Intraepithelial neoplasia involved the mucosa of UBS in 10 cases; this may pose diagnostic problems with invasive carcinoma. Furthermore, UBS were often associated with mucosal redundancy and hypertrophy of the muscularis propria, therefore mimicking muscle invasive cancer on pelvic examination and imaging techniques. Recognition of UBS is important to pathologically and clinically avoid over-staging of bladder malignancies.