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inverted urothelial papilloma

Sunday 30 September 2012

urothelial inverted papilloma

Definition: Inverted papilloma of the urinary bladder is rare, accounting for @<@1% of all bladder neoplasms. Although there is general consensus that inverted papilloma is benign in nature, little is known about its pathogenesis.

Images

- Inverted urothelial papilloma - anastomosing cords of urothelium, cytologically bland, peripheral palisading

Digital images

- JRC:2819 : Bladder inverted papilloma (56 y M. Gross painless hematuria)

Microscopy

The bladder surface is covered by benign, reactive urothelium. The cells are hyperchromatic, but predominantly well organized and not pleomorphic. The underlying stroma (lamina propria) contains papillary structures with fibrovascular cores, each with an intact basement membrane. The lesion is most consistent with in inverted papilloma.

Localization

- vesical inverted papilloma (bladder inverted papilloma)

Etiology

- Not linked to Human Papillomavirus (HPV) (23681080)

Differential diagnosis

-  cystitis cystica et glandularis

  • Cystitis cystica et glandularis refers to Brunn’s nests in the lamina propria with cystic spaces, and other glands with cuboidal to columnar epithelium.
  • Intestinal type contains Goblet cells.

- urothelial hyperplasia

  • Urothelial hyperplasia (flat urothelial hyperplasia) refers to the layer of urothelium above the basement membrane - not within the lamina propria.
  • It is thickened (has an increased number of layers), without structural or cytologic atypia.

- low-grade papillary urothelial cell carcinoma

  • Low grade papillary urothelial cell carcinoma is less organized i.e. the cells have do not line up in as much of a “picket fence” arrangement, particularly towards the basement membrane.

References

- Human Papillomavirus is Not an Etiologic Agent of Urothelial Inverted Papillomas. Alexander RE, Davidson DD, Lopez-Beltran A, Montironi R, Maclennan GT, Compérat E, Idrees MT, Emerson RE, Cheng L. Am J Surg Pathol. 2013 May 15. PMID: 23681080