Benign Tumor Mimicking Invasive Urothelial Carcinoma: Inverted Urothelial Papilloma of the Bladder

Inverted urothelial papilloma is a benign neoplasm with endophytic development and anastomosed insular and trabecular architecture. The objectives of our work are to report a case of inverted papilloma.

A 72-year-old patient with no significant medical history was presented with macroscopic hematuria with no other associated urinary or extra-urinary signs. The physical examination was unremarkable. Cystoscopic exploration revealed an intravesical polyp that was resected. Macroscopic examination showed a polypoid fragment measuring 2mm. Microscopic examination revealed urothelial mucosa with benign tumor proliferation with endophytic development. It consisted of nests, cords, and anastomosed trabeculae. The cells were of medium size with regular nuclei devoid of atypia (Figures 1&2). The conclusion favored a completely excised inverted urothelial papilloma. Followup was indicated. The evolution was unremarkable.

Inverted urothelial papilloma is a benign neoplasm with endophytic development and anastomosed insular and trabecular architecture [1]. Inverted papilloma of the bladder is a rare benign tumor representing 1 to 2.2% of bladder tumors [2]. Inverted papilloma of the bladder typically appears in the fifth and sixth decades of life with a mean age of 59 years, with significant male predominance and a sex ratio ranging from 5 to 8 [3]. Our patient had macroscopic hematuria alone or associated with other urinary signs, which is the revealing sign in more than 50% of cases [4], as was the case with our patient. Cystoscopic appearance is in the form of a non-invasive polypoid tumor in the trigone and vesical neck, which remain the preferential locations with a frequency of 84.5% [5-7]. The diagnostic criteria in the 2022 WHO classification of urinary tract tumors are the presence of benign urothelial tumor proliferation with endophytic development, and squamous metaplasia is possible. The main differential diagnosis is invasive urothelial carcinoma due to the endophytic development of the tumor and the presence of cytonuclear atypia that distinguishes it. Treatment relies on endoscopic resection with surveillance by flexible cystoscopy every 4 months in the first year and then every 6 months for the next 3 years. Systematic surveillance of the upper urinary tract is not deemed necessary [8,9], given the risk of association with urothelial carcinoma.

Inverted papilloma is a rare tumor that remains unfamiliar to urologists and poses a problem of differential diagnosis with urothelial carcinomas for pathologists. Association with malignant tumors is not uncommon and requires regular surveillance (Figures1&2).

None.

No conflict of interest.