Friday 24 May 2013
Urothelial papilloma should be distinguished from "papillary urothelial neoplasm of low malignant potential" (PUNLMP) (WHO/ISUP Classification, 1998) (formerly Grade 1 (of 3) papillary transitional cell carcinoma, WHO Classification, 1973).
Urothelial papilloma consists of papillary fronds containing delicate fibrovascular cores lined by less than 7 layers of cytologically and architecturally normal urothelium. Prominent cytoplasmic vacuoles are seen.
Using criteria recommended by WHO, urothelial papilloma comprises less than 3% of papillary urothelial neoplasms. Usually, they are small solitary papillary lesions (less than 2 cm in size).
Prominent cytoplasmic vacuoles are seen.
The absence of cytologic atypia or mitotic figures can be noted.
Some authors propose expanding the category of urothelial papilloma to include most WHO Grade 1 urothelial carcinoma – a proposal not favored by most pathologists.
Cytologically and architecturally normal urothelium lining the papillary frond can be noted.
Urothelial papilloma is considered to be a benign lesion with infrequent recurrences and exceedingly low risk of development of urothelial carcinoma. (Cheng et al. Urothelial papilloma of the bladder. Cancer 1999; 86:2098-101)
Urothelial (Transitional Cell) Papilloma of the Urinary Bladder: A Clinicopathologic Study of 26 Cases. Mod Pathol 2003;16(7):623–629 - http://www.nature.com/modpathol/journal/v16/n7/full/3880815a.html