Brunn cysts or mucous cysts of the urinary bladder are considered to originate from von Brunn nests as the result of pinching off of epithelial nests from urothelial buds. Cysts in the urinary bladder are considered as tumor-like lesions.
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Clinical presentation
Most Brunn cysts are asymptomatic, rarely they can result in bladder outlet obstruction in males 3,4.
Differential diagnosis
urachal cysts: typically in the dome and anterior wall
cloacal cysts are confined to the posterior wall
other cystic lesions, e.g. dermoid cyst, Mullerian duct cyst, seminal vesicle cyst, ureterocele and hydatid cyst
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nested variant of urothelial carcinoma (NVUC)
rare tumor with an incidence of 0.3% of invasive bladder tumors
on microscopy, bladders with florid proliferations of von Brunn nests show larger cell nests with regular shape and spacing compared to smaller, irregular nests of NVUC with irregular spacing and infiltrative base; the presence of muscle invasion proper is a key distinguishing feature
History and etymology
Brunn cysts were first described in 1988 by Israel Franco that considered it a pinched off portion of urothelial epithelium and hypothesized the origin as congenital.