inverted urothelial 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.

See also : inverted papilloma

Images

 Inverted urothelial papilloma

• https://twitter.com/JennyHoffmannMD/status/851649417467711488
• https://twitter.com/TexPathol/status/1210546184768643073

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.

- anastomosing cords of urothelium, cytologically bland, peripheral palisading

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