Bladder & urothelial tract
Urothelial carcinoma - invasive
Inverted growth pattern
Author: Monika Roychowdhury, M.D.
Last author update: 1 December 2014
Last staff update: 9 December 2024 (update in progress)
Copyright: 2003-2024, PathologyOutlines.com, Inc.
PubMed Search: Inverted growth pattern [title]
Table of Contents
Definition / general | Epidemiology | Clinical features | Microscopic (histologic) description | Differential diagnosisCite this page: Roychowdhury M Inverted growth pattern. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/bladderendophyticgrowth.html. Accessed December 28th, 2024.
Definition / general
- Inverted (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
Epidemiology
- 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 2012;30:49)
Microscopic (histologic) description
- 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
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
