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urothelial papilloma

Friday 24 May 2013


Definition : Urothelial papillomas do not show any appreciable thickening of the lining urothelium.

Cross-sectional view of papillary fronds showing showing 4 to 6 layers of normal-appearing urothelium. In some cases, tangential sectioning may give a false impression of increased urothelial thickness.

The umbrella cells show prominent vacuolization in some fronds. Urothelial papillomas pursue a benign clinical course and recur uncommonly. In rare cases, they progress to higher-grade lesions.

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.

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).

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).


- papilloma of the bladder, vacuolisation of superficial cells

- Urothelial papilloma

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)

See also

- papilloma

Open references

- Urothelial (Transitional Cell) Papilloma of the Urinary Bladder: A Clinicopathologic Study of 26 Cases. Mod Pathol 2003;16(7):623–629 -