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Urothelial carcinoma

Endophytic growth pattern

Reviewer: Monika Roychowdhury, M.D., University of Minnesota Medical Center (see Reviewers page)
Revised: 3 July 2011, last major update April 2011
Copyright: (c) 2003-2011, PathologyOutlines.com, Inc.


● Endophytic growth pattern can be associated with papilloma, urothelial neoplasm of low malignant potential, low / high grade tumors that are noninvasive or invasive; this topic discusses invasive tumors
● Anastomosing cords and columns of urothelium resembling inverted papilloma or broad pushing bulbous invaginations into lamina propria (broad front pattern), but with definitive evidence of invasion
● Not a WHO diagnosis


● Mean age 68 years
● 75% male

Clinical features

● Pattern present in 11% of urothelial carcinomas
● Associated with high grade and high stage tumors, and possibly poorer prognosis (Urol Oncol 2010 Mar 5 [Epub ahead of print])


● Anastomosing cords and columns of urothelium resembling inverted papilloma or broad pushing bulbous invaginations into lamina propria (broad front pattern)
● The trabecuale are wider and more irregular than those of inverted papilloma
● Invasive if there is irregularity of broad front of bulbous invaginations, retraction artifact, desmoplasia or other features of destructive invasion
● Usually exophytic papillary urothelial carcinoma is also present
● Substantial nuclear pleomorphism, readily apparent mitotic figures and architectural abnormalities
● At least 25% of tumor should have an inverted component to be considered as inverted urothelial carcinoma (BJU Int 2011;107:532)
● Findings suggestive of invasion irregularly shaped nests with disruption or absence of the basement membrane, desmoplasia or fibrotic stromal response (note that microinvasion usually does not elicit a stromal response, which makes its identification more difficult)
● Pattern is associated with invasion in 50% of papillary urothelial carcinomas (Am J Surg Pathol 1997;21:1057)
● Urothelial carcinoma in situ, if present in the surface urothelium, provides support for a diagnosis of inverted urothelial carcinoma

Micro images

Non-invasive and invasive

Differential diagnosis

Inverted papilloma: may have focal papillary pattern; normal bland urothelium with occasional umbrella cells, no invasion (Ann Diagn Pathol 2009;13:158); negative for Ki-67, CK20, p53; normal FISH (Am J Surg Pathol 2007;31:1861)
● Inverted papilloma with atypia: rare mitotic figures and very low proliferation rate as estimated by Ki-67 immunostaining

End of Bladder > Urothelial carcinoma > Endophytic growth pattern

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