Anatomical Pathology Interesting Case Conference

Microscopic Description:

Histology revealed invaginating polypoid proliferation of anastomosing cords and trabeculae with peripheral palisading of cells, central streaming of urothelial cells is also seen.

IHC: CK 20-.

Discussion:

Inverted papilloma is a rare non-invasive, benign, endophytic urothelial tumor of the urinary bladder caused due to chronic inflammation. It is mostly an incidental finding during cystoscopy. It often presents as intermittent, gross, painless hematuria.

Grossly, it can be single (more likely) or multiple, sessile, pedunculated or polypoid mass with smooth surface. The size range is from 1 to 80 mm.

Microscopically, It shows circumscribed mass with trabecular growth pattern. The anastomosing cords and trabeculae of uniform width from the urothelium invaginate into the lamina propria. The central portion of the tumor has spindle-shaped cells parallel to the cords (streaming).

 

IHC: CK 20-, low Ki-67 positivity.

Treatment involves complete transurethral resection of the lesion.

It is a risk factor for transitional cell urothelial carcinoma (2.5-10%) and has a risk of recurrence of < 5%. Henceforth, timely follow up cystoscopy is required.

References:
 

Sweeney MK, Rais-Bahrami S, Gordetsky J. Inverted urothelial papilloma: A review of diagnostic pitfalls and clinical management. Can Urol Assoc J. 2017 Jan-Feb;11(1-2):66-69.

Rahman, Mohammad Ekhlasur, Muhammad Rakib Hasan, Mahabub Hassan, Kashif Waheed, Angelos Christofides, and Bharati Tripathi. 2025. “Unveiling an Inverted Papilloma of the Bladder: A Case Series and Literature Review.” Cureus 17 (10): e95417–17.

 

Patel P, Reikie BA, Maxwell JP. Long-term clinical outcome of inverted urothelial papilloma including cases with focal papillary pattern: Is continuous surveillance necessary? Urology. 2013;82:857–60. doi: 10.1016/j.urology.2013.06.040.

Guo A, Liu A, Teng X. The pathology of urinary bladder lesions with an inverted growth pattern. Chin J Cancer Res. 2016;28:107–21. doi: 10.3978/j.issn.1000-9604.2016.02.01.

Brown AL, Cohen RJ. Inverted papilloma of the urinary tract. BJU Int. 2010;107:24–6. doi: 10.1111/j.1464-410X.2011.10046.x.

Broussard JN, Tan PH, Epstein JI, et al. Atypia in inverted urothelial papillomas: Pathology and prognostic significance. Hum Pathol. 2004;35:1499–1504. doi: 10.1016/j.humpath.2004.09.010.

 

Case Images