Scanning electron microscopy was performed on forceps biopsies from 13 patients with catheter-associated polypoid cystitis. Pleomorphic microvilli, which varied considerably in appearance, were found on surface cells of all cases with polypoid cystitis. Practically all of the characteristics of pleomorphic microvilli assigned earlier to bladder tumor cells in humans were identified on specimens from patients with polypoid cystitis. Pleomorphic microvilli were not observed in the bladder biopsies from control patients. The appearance of pleomorphic microvilli was consistent with reversible lesions of the human bladder and they are not specific markers of pre-neoplastic hyperplasia or malignancy.
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