The Prevalence and Significance of Brunn’s Nests, Cystitis Cystica and Squamous Metaplasia in Normal Bladders

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Abstract
The frequency of Brunn''s nests, cystitis cystica and squamous metaplasia was studied by multiple histologic sections in 100 grossly normal bladders obtained at postmortem examination. Of the 100 bladders, 93% had at least 1 of the 3 proliferative changes. Brunn''s nests and cystitis cystica were seen in 89 and 60% of the bladders, respectively, most often at the bladder neck and trigone. Non-keratinizing squamous metaplasia of the vaginal type was seen almost exclusively on the trigone and bladder neck in 46% of the premenopausal and postmenopausal women but in only 7% of the men. There was no satisfactory evidence that inflammation was causally associated with these changes. Brunn''s nests, cystitis cystica and squamous metaplasia of the vaginal type in women appear to be normal variants of bladder urothelium and have no precancerous potential.