Inverted urothelial papilloma

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Inverted urothelial papilloma
Diagnosis in short

Inverted urothelial papilloma. H&E stain.

LM like papillomas... but grow downward; never have an exophytic component; nests have peripheral palisading of nuclei - important
LM DDx low grade papillary urothelial carcinoma with an inverted growth pattern
IHC Ki-67 -ve, CK20 -ve, p53 -ve (rarely +ve)
Site urothelium - usu. urinary bladder

Prevalence uncommon
Prognosis benign

Inverted urothelial papilloma, also inverted papilloma, is a benign urothelial lesion that may be confused with urothelial carcinoma.


  • May be confused with papillary urothelial carcinoma with an inverted growth pattern.



  • Like papillomas... but grow downward.[1]
  • According to THvdK,[2] inverted papillomas never have an exophytic component; if an exophytic component is present it is urothelial carcinoma. This is disputed by one paper from Mexico that examines two cases.[3]
  • Nests have peripheral palisading of nuclei - important.



Case 1

Case 2


May be useful versus inverted growth pattern UCC:[4]

  • Ki-67 -ve.
  • CK20 -ve.
  • p53 -ve (rarely +ve).

See also

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Bladder Tumour, Transurthral Resection:
     - Inverted papilloma.


The sections show urothelial mucosa with a densely packed urothelial nests with peripheral palisading. The cells of the urothelial nests are bland. Proliferative activity is not apparent. Definite papillae are absent. No exophytic component is apparent.


  1. Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 310. ISBN 978-0781765275.
  2. THvdK. 21 June 2010.
  3. Albores-Saavedra J, Chable-Montero F, Hernández-Rodríguez OX, Montante-Montes de Oca D, Angeles-Angeles A (June 2009). "Inverted urothelial papilloma of the urinary bladder with focal papillary pattern: a previously undescribed feature". Ann Diagn Pathol 13 (3): 158–61. doi:10.1016/j.anndiagpath.2009.02.009. PMID 19433293.
  4. Jones, TD.; Zhang, S.; Lopez-Beltran, A.; Eble, JN.; Sung, MT.; MacLennan, GT.; Montironi, R.; Tan, PH. et al. (Dec 2007). "Urothelial carcinoma with an inverted growth pattern can be distinguished from inverted papilloma by fluorescence in situ hybridization, immunohistochemistry, and morphologic analysis.". Am J Surg Pathol 31 (12): 1861-7. doi:10.1097/PAS.0b013e318060cb9d. PMID 18043040.