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.

General

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

Microscopic

Features:

  • 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.

DDx:

Images

Case 1

Case 2

IHC

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

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

See also

References

  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.